Electric Field Effect in Atomically Thin Carbon Films

We describe monocrystalline graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar electric field effect such that electrons and holes in concentrations up to 10 13 per square centimeter and with room-temperature mobilities of ∼10,000 square centimeters per volt-second can be induced by applying gate voltage.

Positional cloning of the mouse obese gene and its human homologue

The mechanisms that balance food intake and energy expenditure determine who will be obese and who will be lean. One of the molecules that regulates energy balance in the mouse is the obese (ob) gene. Mutation of ob results in profound obesity and type II diabetes as part of a syndrome that resembles morbid obesity in humans. The ob gene product may function as part of a signalling pathway from adipose tissue that acts to regulate the size of the body fat depot.

Segmentation of brain MR images through a hidden Markov random field model and the expectation-maximization algorithm

The finite mixture (FM) model is the most commonly used model for statistical segmentation of brain magnetic resonance (MR) images because of its simple mathematical form and the piecewise constant nature of ideal brain MR images. However, being a histogram-based model, the FM has an intrinsic limitation--no spatial information is taken into account. This causes the FM model to work only on well-defined images with low levels of noise; unfortunately, this is often not the the case due to artifacts such as partial volume effect and bias field distortion. Under these conditions, FM model-based methods produce unreliable results. In this paper, we propose a novel hidden Markov random field (HMRF) model, which is a stochastic process generated by a MRF whose state sequence cannot be observed directly but which can be indirectly estimated through observations. Mathematically, it can be shown that the FM model is a degenerate version of the HMRF model. The advantage of the HMRF model derives from the way in which the spatial information is encoded through the mutual influences of neighboring sites. Although MRF modeling has been employed in MR image segmentation by other researchers, most reported methods are limited to using MRF as a general prior in an FM model-based approach. To fit the HMRF model, an EM algorithm is used. We show that by incorporating both the HMRF model and the EM algorithm into a HMRF-EM framework, an accurate and robust segmentation can be achieved. More importantly, the HMRF-EM framework can easily be combined with other techniques. As an example, we show how the bias field correction algorithm of Guillemaud and Brady (1997) can be incorporated into this framework to achieve a three-dimensional fully automated approach for brain MR image segmentation.

Gut microbiome modulates response to anti-PD-1 immunotherapy in melanoma patients

Preclinical mouse models suggest that the gut microbiome modulates tumor response to checkpoint blockade immunotherapy; however, this has not been well-characterized in human cancer patients. Here we examined the oral and gut microbiome of melanoma patients undergoing anti-programmed cell death 1 protein (PD-1) immunotherapy (n = 112). Significant differences were observed in the diversity and composition of the patient gut microbiome of responders versus nonresponders. Analysis of patient fecal microbiome samples (n = 43, 30 responders, 13 nonresponders) showed significantly higher alpha diversity (P < 0.01) and relative abundance of bacteria of the Ruminococcaceae family (P < 0.01) in responding patients. Metagenomic studies revealed functional differences in gut bacteria in responders, including enrichment of anabolic pathways. Immune profiling suggested enhanced systemic and antitumor immunity in responding patients with a favorable gut microbiome as well as in germ-free mice receiving fecal transplants from responding patients. Together, these data have important implications for the treatment of melanoma patients with immune checkpoint inhibitors.

Protein translation and folding are coupled by an endoplasmic-reticulum-resident kinase

Protein synthesis and the folding of the newly synthesized proteins into the correct three-dimensional structure are coupled in cellular compartments of the exocytosis pathway by a process that modulates the phosphorylation level of eukaryotic initiation factor-2alpha (eIF2alpha) in response to a stress signal from the endoplasmic reticulum (ER). Activation of this process leads to reduced rates of initiation of protein translation during ER stress. Here we describe the cloning of perk, a gene encoding a type I transmembrane ER-resident protein. PERK has a lumenal domain that is similar to the ER-stress-sensing lumenal domain of the ER-resident kinase Ire1, and a cytoplasmic portion that contains a protein-kinase domain most similar to that of the known eIF2alpha kinases, PKR and HRI. ER stress increases PERK's protein-kinase activity and PERK phosphorylates eIF2alpha on serine residue 51, inhibiting translation of messenger RNA into protein. These properties implicate PERK in a signalling pathway that attenuates protein translation in response to ER stress.

Leptin levels in human and rodent: measurement of plasma leptin and ob RNA in obese and weight-reduced subjects

Leptin, the gene product of the obese gene, may play an important role in regulating body weight by signalling the size of the adipose tissue mass. Plasma leptin was found to be highly correlated with body mass index (BMI) in rodents and in 87 lean and obese humans. In humans, there was variability in plasma leptin at each BMI suggesting that there are differences in its secretion rate from fat. Weight loss due to food restriction was associated with a decrease in plasma leptin in samples from mice and obese humans.

Regulated translation initiation controls stress-induced gene expression in mammalian cells

Protein kinases that phosphorylate the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha) are activated in stressed cells and negatively regulate protein synthesis. Phenotypic analysis of targeted mutations in murine cells reveals a novel role for eIF2alpha kinases in regulating gene expression in the unfolded protein response (UPR) and in amino acid starved cells. When activated by their cognate upstream stress signals, the mammalian eIF2 kinases PERK and GCN2 repress translation of most mRNAs but selectively increase translation of Activating Transcription Factor 4 (ATF4), resulting in the induction of the downstream gene CHOP (GADD153). This is the first example of a mammalian signaling pathway homologous to the well studied yeast general control response in which eIF2alpha phosphorylation activates genes involved in amino acid biosynthesis. Mammalian cells thus utilize an ancient pathway to regulate gene expression in response to diverse stress signals.

Coupling of stress in the ER to activation of JNK protein kinases by transmembrane protein kinase IRE1

Malfolded proteins in the endoplasmic reticulum (ER) induce cellular stress and activate c-Jun amino-terminal kinases (JNKs or SAPKs). Mammalian homologs of yeast IRE1, which activate chaperone genes in response to ER stress, also activated JNK, and IRE1alpha-/- fibroblasts were impaired in JNK activation by ER stress. The cytoplasmic part of IRE1 bound TRAF2, an adaptor protein that couples plasma membrane receptors to JNK activation. Dominant-negative TRAF2 inhibited activation of JNK by IRE1. Activation of JNK by endogenous signals initiated in the ER proceeds by a pathway similar to that initiated by cell surface receptors in response to extracellular signals.

Dynamic interaction of BiP and ER stress transducers in the unfolded-protein response

PERK and IRE1 are type-I transmembrane protein kinases that reside in the endoplasmic reticulum (ER) and transmit stress signals in response to perturbation of protein folding. Here we show that the lumenal domains of these two proteins are functionally interchangeable in mediating an ER stress response and that, in unstressed cells, both lumenal domains form a stable complex with the ER chaperone BiP. Perturbation of protein folding promotes reversible dissociation of BiP from the lumenal domains of PERK and IRE1. Loss of BiP correlates with the formation of high-molecular-mass complexes of activated PERK or IRE1, and overexpression of BiP attenuates their activation. These findings are consistent with a model in which BiP represses signalling through PERK and IRE1 and protein misfolding relieves this repression by effecting the release of BiP from the PERK and IRE1 lumenal domains.

Prognostic factors analysis of 17,600 melanoma patients: validation of the American Joint Committee on Cancer melanoma staging system

PURPOSE

The American Joint Committee on Cancer (AJCC) recently proposed major revisions of the tumor-node-metastases (TNM) categories and stage groupings for cutaneous melanoma. Thirteen cancer centers and cancer cooperative groups contributed staging and survival data from a total of 30,450 melanoma patients from their databases in order to validate this staging proposal.

PATIENTS AND METHODS

There were 17,600 melanoma patients with complete clinical, pathologic, and follow-up information. Factors predicting melanoma-specific survival rates were analyzed using the Cox proportional hazards regression model. Follow-up survival data for 5 years or longer were available for 73% of the patients.

RESULTS

This analysis demonstrated that (1) in the T category, tumor thickness and ulceration were the most powerful predictors of survival, and the level of invasion had a significant impact only within the subgroup of thin (< or = 1 mm) melanomas; (2) in the N category, the following three independent factors were identified: the number of metastatic nodes, whether nodal metastases were clinically occult or clinically apparent, and the presence or absence of primary tumor ulceration; and (3) in the M category, nonvisceral metastases was associated with a better survival compared with visceral metastases. A marked diversity in the natural history of pathologic stage III melanoma was demonstrated by five-fold differences in 5-year survival rates for defined subgroups. This analysis also demonstrated that large and complex data sets could be used effectively to examine prognosis and survival outcome in melanoma patients.

CONCLUSION

The results of this evidence-based methodology were incorporated into the AJCC melanoma staging as described in the companion publication.

Osteoarthritis: new insights. Part 1: the disease and its risk factors

Osteoarthritis is the most common form of arthritis, affecting millions of people in the United States. It is a complex disease whose etiology bridges biomechanics and biochemistry. Evidence is growing for the role of systemic factors (such as genetics, dietary intake, estrogen use, and bone density) and of local biomechanical factors (such as muscle weakness, obesity, and joint laxity). These risk factors are particularly important in weight-bearing joints, and modifying them may present opportunities for prevention of osteoarthritis-related pain and disability. Major advances in management to reduce pain and disability are yielding a panoply of available treatments ranging from nutriceuticals to chondrocyte transplantation, new oral anti-inflammatory medications, and health education. This article is part 1 of a two-part summary of a National Institutes of Health conference. The conference brought together experts on osteoarthritis from diverse backgrounds and provided a multidisciplinary and comprehensive summary of recent advances in the prevention of osteoarthritis onset, progression, and disability. Part 1 focuses on a new understanding of what osteoarthritis is and on risk factors that predispose to disease occurrence. It concludes with a discussion of the impact of osteoarthritis on disability.

Perk is essential for translational regulation and cell survival during the unfolded protein response

Malfolded proteins in the endoplasmic reticulum (ER) inhibit translation initiation. This response is believed to be mediated by increased phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha) and is hypothesized to reduce the work load imposed on the folding machinery during stress. Here we report that mutating the gene encoding the ER stress-activated eIF2alpha kinase PERK abolishes the phosphorylation of eIF2alpha in response to accumulation of malfolded proteins in the ER resulting in abnormally elevated protein synthesis and higher levels of ER stress. Mutant cells are markedly impaired in their ability to survive ER stress and inhibition of protein synthesis by cycloheximide treatment during ER stress ameliorates this impairment. PERK thus plays a major role in the ability of cells to adapt to ER stress.

Observation of Gravitational Waves from a Binary Black Hole Merger

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

Pulmonary expression of interleukin-13 causes inflammation, mucus hypersecretion, subepithelial fibrosis, physiologic abnormalities, and eotaxin production

Interleukin (IL)-13 is a pleiotropic cytokine produced in large quantities by activated CD4(+) Th2 lymphocytes. To define further its potential in vivo effector functions, the Clara cell 10-kDa protein promoter was used to express IL-13 selectively in the lung, and the phenotype of the resulting transgenic mice was characterized. In contrast to transgene-negative littermates, the lungs of transgene-positive mice contained an inflammatory response around small and large airways and in the surrounding parenchyma. It was mononuclear in nature and contained significant numbers of eosinophils and enlarged and occasionally multinucleated macrophages. Airway epithelial cell hypertrophy, mucus cell metaplasia, the hyperproduction of neutral and acidic mucus, the deposition of Charcot-Leyden-like crystals, and subepithelial airway fibrosis were also prominently noted. Eotaxin protein and mRNA were also present in large quantities in the lungs of the transgene-positive, but not the transgene-negative, mice. IL-4, IL-5, granulocyte-macrophage colony-stimulating factor, and monocyte chemoattractant protein-5 were not similarly detected. Physiological evaluations revealed significant increases in baseline airways resistance and airways hyperresponsiveness (AHR) to methacholine in transgene-positive animals. Thus, the targeted pulmonary expression of IL-13 causes a mononuclear and eosinophilic inflammatory response, mucus cell metaplasia, the deposition of Charcot-Leyden-like crystals, airway fibrosis, eotaxin production, airways obstruction, and nonspecific AHR. IL-13 may play an important role in the pathogenesis of similar responses in asthma or other Th2-polarized tissue responses.

Disruption of IRS-2 causes type 2 diabetes in mice

Human type 2 diabetes is characterized by defects in both insulin action and insulin secretion. It has been difficult to identify a single molecular abnormality underlying these features. Insulin-receptor substrates (IRS proteins) may be involved in type 2 diabetes: they mediate pleiotropic signals initiated by receptors for insulin and other cytokines. Disruption of IRS-1 in mice retards growth, but diabetes does not develop because insulin secretion increases to compensate for the mild resistance to insulin. Here we show that disruption of IRS-2 impairs both peripheral insulin signalling and pancreatic beta-cell function. IRS-2-deficient mice show progressive deterioration of glucose homeostasis because of insulin resistance in the liver and skeletal muscle and a lack of beta-cell compensation for this insulin resistance. Our results indicate that dysfunction of IRS-2 may contribute to the pathophysiology of human type 2 diabetes.

Mammalian sweet taste receptors

The sense of taste provides animals with valuable information about the quality and nutritional value of food. Previously, we identified a large family of mammalian taste receptors involved in bitter taste perception (the T2Rs). We now report the characterization of mammalian sweet taste receptors. First, transgenic rescue experiments prove that the Sac locus encodes T1R3, a member of the T1R family of candidate taste receptors. Second, using a heterologous expression system, we demonstrate that T1R2 and T1R3 combine to function as a sweet receptor, recognizing sweet-tasting molecules as diverse as sucrose, saccharin, dulcin, and acesulfame-K. Finally, we present a detailed analysis of the patterns of expression of T1Rs and T2Rs, thus providing a view of the representation of sweet and bitter taste at the periphery.

ARF promotes MDM2 degradation and stabilizes p53: ARF-INK4a locus deletion impairs both the Rb and p53 tumor suppression pathways

The INK4a-ARF locus encodes two unrelated proteins that both function in tumor suppression. p16INK4 binds to and inhibits the activity of CDK4 and CDK6, and ARF arrests the cell cycle in a p53-dependent manner. We show here that ARF binds to MDM2 and promotes the rapid degradation of MDM2. This interaction is mediated by the exon 1beta-encoded N-terminal domain of ARF and a C-terminal region of MDM2. ARF-promoted MDM2 degradation is associated with MDM2 modification and concurrent p53 stabilization and accumulation. The functional consequence of ARF-regulated p53 levels via MDM2 proteolysis is evidenced by the ability of ectopically expressed ARF to restore a p53-imposed G1 cell cycle arrest that is otherwise abrogated by MDM2. Thus, deletion of the ARF-INK4a locus simultaneously impairs both the INK4a-cyclin D/CDK4-RB and the ARF-MDM2-p53 pathways.

Significant acidification in major Chinese croplands

Soil acidification is a major problem in soils of intensive Chinese agricultural systems. We used two nationwide surveys, paired comparisons in numerous individual sites, and several long-term monitoring-field data sets to evaluate changes in soil acidity. Soil pH declined significantly (P < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. Processes related to nitrogen cycling released 20 to 221 kilomoles of hydrogen ion (H+) per hectare per year, and base cations uptake contributed a further 15 to 20 kilomoles of H+ per hectare per year to soil acidification in four widespread cropping systems. In comparison, acid deposition (0.4 to 2.0 kilomoles of H+ per hectare per year) made a small contribution to the acidification of agricultural soils across China.

A major inducer of anticarcinogenic protective enzymes from broccoli: isolation and elucidation of structure

Consumption of vegetables, especially crucifers, reduces the risk of developing cancer. Although the mechanisms of this protection are unclear, feeding of vegetables induces enzymes of xenobiotic metabolism and thereby accelerates the metabolic disposal of xenobiotics. Induction of phase II detoxication enzymes, such as quinone reductase [NAD(P)H:(quinone-acceptor) oxidoreductase, EC 1.6.99.2] and glutathione S-transferases (EC 2.5.1.18) in rodent tissues affords protection against carcinogens and other toxic electrophiles. To determine whether enzyme induction is responsible for the protective properties of vegetables in humans requires isolation of enzyme inducers from these sources. By monitoring quinone reductase induction in cultured murine hepatoma cells as the biological assay, we have isolated and identified (-)-1-isothiocyanato-(4R)-(methylsulfinyl)butane [CH3-SO-(CH2)4-NCS, sulforaphane] as a major and very potent phase II enzyme inducer in SAGA broccoli (Brassica oleracea italica). Sulforaphane is a monofunctional inducer, like other anticarcinogenic isothiocyanates, and induces phase II enzymes selectively without the induction of aryl hydrocarbon receptor-dependent cytochromes P-450 (phase I enzymes). To elucidate the structural features responsible for the high inducer potency of sulforaphane, we synthesized racemic sulforaphane and analogues differing in the oxidation state of sulfur and the number of methylene groups: CH3-SOm-(CH2)n-NCS, where m = 0, 1, or 2 and n = 3, 4, or 5, and measured their inducer potencies in murine hepatoma cells. Sulforaphane is the most potent inducer, and the presence of oxygen on sulfur enhances potency. Sulforaphane and its sulfide and sulfone analogues induced both quinone reductase and glutathione transferase activities in several mouse tissues. The induction of detoxication enzymes by sulforaphane may be a significant component of the anticarcinogenic action of broccoli.

The effects of specific medical conditions on the functional limitations of elders in the Framingham Study

OBJECTIVES

The purpose of this study was to identify associations between specific medical conditions in the elderly and limitations in functional tasks; to compare risks of disability across medical conditions, controlling for age, sex, and comorbidity; and to determine the proportion of disability attributable to each condition.

METHODS

The subjects were 709 noninstitutionalized men and 1060 women of the Framingham Study cohort (mean age 73.7 +/- 6.3 years). Ten medical conditions were identified for study: knee osteoarthritis, hip fracture, diabetes, stroke, heart disease, intermittent claudication, congestive heart failure, chronic obstructive pulmonary disease, depressive symptomatology, and cognitive impairment. Adjusted odds ratios were calculated for dependence on human assistance in seven functional activities.

RESULTS

Stroke was significantly associated with functional limitations in all seven tasks; depressive symptomatology and hip fracture were associated with limitations in five tasks; and knee osteoarthritis, heart disease, congestive heart failure, and chronic obstructive pulmonary disease, were associated with limitations in four tasks each.

CONCLUSIONS

In general, stroke, depressive symptomatology, hip fracture, knee osteoarthritis, and heart disease account for more physical disability in noninstitutionalized elderly men and women than other diseases.

Pharmacological and biochemical demonstration of the role of cyclooxygenase 2 in inflammation and pain

Nonsteroidal antiinflammatory drugs (NSAIDs) are widely used for the treatment of inflammatory diseases, but significant side effects such as gastrointestinal erosion and renal damage limit their use. NSAIDs inhibit the enzyme cyclooxygenase (COX), which catalyzes the conversion of arachidonic acid to prostaglandins (PGs) and thromboxane. Two forms of COX have been identified--COX-1, which is constitutively expressed in most tissues and organs, and the inducible enzyme, COX-2, which has been localized primarily to inflammatory cells and tissues. In an animal model of acute inflammation (injection of carrageenan into the footpad), edema was produced that was associated with marked accumulation of COX-2 mRNA and thromboxane. A selective inhibitor of COX-2 (SC-58125) inhibited edema at the inflammatory site and was analgesic but had no effect on PG production in the stomach and did not cause gastric toxicity. These data suggest that selective inhibition of COX-2 may produce superior antiinflammatory drugs with substantial safety advantages over existing NSAIDs.