Water microdroplets containing graphene oxide and a second solute are shown to spontaneously segregate into sack-cargo nanostructures upon drying. Analytical modelling and molecular dynamics suggest the sacks form when slow-diffusing graphene oxide preferentially accumulates and adsorbs at the receding air-water interface, followed by capillary collapse. Cargo-filled graphene nanosacks can be nanomanufactured by a simple, continuous, scalable process and are promising for many applications where nanoscale materials should be isolated from the environment or biological tissue.

Sirt1 is an evolutionarily conserved NAD+ dependent deacetylase involved in a wide range of processes including cellular differentiation, apoptosis, as well as metabolism, and aging. In this study, we investigated the role of hypothalamic Sirt1 in energy balance. Pharmacological inhibition or siRNA mediated knock down of hypothalamic Sirt1 showed to decrease food intake and body weight gain. Central administration of a specific melanocortin antagonist, SHU9119, reversed the anorectic effect of hypothalamic Sirt1 inhibition, suggesting that Sirt1 regulates food intake through the central melanocortin signaling. We also showed that fasting increases hypothalamic Sirt1 expression and decreases FoxO1 (Forkhead transcription factor) acetylation suggesting that Sirt1 regulates the central melanocortin system in a FoxO1 dependent manner. In addition, hypothalamic Sirt1 showed to regulate S6K signaling such that inhibition of the fasting induced Sirt1 activity results in up-regulation of the S6K pathway. Thus, this is the first study providing a novel role for the hypothalamic Sirt1 in the regulation of food intake and body weight. Given the role of Sirt1 in several peripheral tissues and hypothalamus, potential therapies centered on Sirt1 regulation might provide promising therapies in the treatment of metabolic diseases including obesity.

The hypothalamic-pituitary-thyroid axis is down-regulated during starvation, and falling levels of leptin are a critical signal for this adaptation, acting to suppress preprothyrotropin-releasing hormone (prepro-TRH) mRNA expression in the paraventricular nucleus of the hypothalamus. This study addresses the mechanism for this regulation, using primary cultures of fetal rat hypothalamic neurons as a model system. Leptin dose-dependently stimulated a 10-fold increase in pro-TRH biosynthesis, with a maximum response at 10 nM. TRH release was quantified using immunoprecipitation, followed by isoelectric focusing gel electrophoresis and specific TRH radioimmunoassay. Leptin stimulated TRH release by 7-fold. Immunocytochemistry revealed that a substantial population of cells expressed TRH or leptin receptors and that 8 -13% of those expressing leptin receptors coexpressed TRH. Leptin produced a 5-fold induction of luciferase activity in CV-1 cells transfected with a TRH promoter and the long form of the leptin receptor cDNA. Although the above data are consistent with a direct ability of leptin to promote TRH biosynthesis through actions on TRH neurons, addition of ␣-melanocyte-stimulating hormone produced a 3.5-fold increase in TRH biosynthesis and release, whereas neuropeptide Y treatment suppressed pro-TRH biosynthesis ϳ3-fold. Furthermore, the melanocortin-4 receptor antagonist SHU9119 partially inhibited leptin-stimulated TRH release from the neuronal culture. Consequently, our data suggest that leptin regulates the TRH neurons through both direct and indirect pathways.Food deprivation in animals and humans results in endocrine and metabolic changes that include decreases in circulating levels of thyroid hormones (1, 2). Previous work in starved rats has shown that this is associated with a decrease in hypothalamic, but not thalamic, reticular prepro-TRH 1 mRNA, supporting the concept that the hypothyroidism of starvation is of hypothalamic origin (1). Leptin is a recently discovered peptide hormone that is synthesized and released by adipose tissue (3-6). Serum leptin levels decrease during starvation, and leptin has been proposed to be a major regulator of the central nervous system-mediated adaptation to starvation (2). Absence of leptin is responsible for the obese phenotype of ob/ob mice, and administration of this hormone to these animals reverses many of the endocrine defects (3-6). It was recently suggested that leptin has an important role in the neuroendocrine regulation of the HPT axis (2,7,8). During prolonged fasting in rats, low levels of triiodothyronine and thyroxine are observed, and TSH is in the low to normal range. This is due in part to fasting-induced suppression of prepro-TRH gene expression in the paraventricular nucleus (PVN) of the hypothalamus neurons. Since the decrease in thyroid hormone levels is blunted in fasted mice and rats by systemic administration of leptin (2, 9), it has been proposed that the decrease in leptin during fasting alters the set point for feedback inhibition by ...

Malignant mesothelioma has been linked to asbestos exposure and generally has a poor prognosis because it is often diagnosed in advanced stages and is refractory to conventional therapy. Human malignant mesotheliomas accumulate multiple somatic genetic alterations, including inactivation of the NF2 and CDKN2A/ARF tumor suppressor genes. To better understand the significance of NF2 inactivation in malignant mesothelioma and identify tumor suppressor gene alterations that cooperate with NF2 loss of function in malignant mesothelioma pathogenesis, we treated Nf 2 (+/À) knockout mice with asbestos to induce malignant mesotheliomas. Asbestos-exposed Nf 2 (+/À) mice exhibited markedly accelerated malignant mesothelioma tumor formation compared with asbestos-treated wild-type (WT) littermates. Loss of the WT Nf 2 allele, leading to biallelic inactivation, was observed in all nine asbestos-induced malignant mesotheliomas from Nf 2 (+/À) mice and in 50% of malignant mesotheliomas from asbestos-exposed WT mice. For a detailed comparison with the murine model, DNA analyses were also done on a series of human malignant mesothelioma samples. Remarkably, similar to human malignant mesotheliomas, tumors from Nf 2 (+/À) mice showed frequent homologous deletions of the Cdkn2a/ Arf locus and adjacent Cdkn2b tumor suppressor gene, as well as reciprocal inactivation of Tp53 in a subset of tumors that retained the Arf locus. As in the human disease counterpart, malignant mesotheliomas from the Nf2 (+/À) mice also showed frequent activation of Akt kinase, which plays a central role in tumorigenesis and therapeutic resistance. Thus, this murine model of environmental carcinogenesis faithfully recapitulates many of the molecular features of human malignant mesothelioma and has significant implications for the further characterization of malignant mesothelioma pathogenesis and preclinical testing of novel therapeutic modalities. (Cancer Res 2005; 65(18): 8090-5)

The ultimate success of many nanotechnologies will depend on our ability to understand and manage nanomaterial health risks. Carbon nanotubes are now primarily fabricated by catalytic routes and typically contain significant quantities of transition metal catalyst residues. Iron-catalyzed free-radical generation has been hypothesized to contribute to oxidative stress and toxicity upon exposure to ambient particulate, amphibole asbestos fibers, and single-wall carbon nanotubes. A key issue surrounding nanotube iron is bioavailability, which has not been systematically characterized, but is widely thought to be low on the basis of electron microscope observations of metal encapsulation by carbon shells. Here, we validate and apply simple acellular assays to show that toxicologically significant amounts of iron can be mobilized from a diverse set of commercial nanotube samples in the presence of ascorbate and the chelating agent ferrozine. This mobilized iron is redox active and induces single-strand breaks in plasmid DNA in the presence of ascorbate. Iron bioavailability varies greatly from sample to sample and cannot be predicted from total iron content. Iron bioavailability is not fully suppressed by vendor "purification" and is sensitive to partial oxidation, mechanical stress, sample age, and intentional chelation. The results suggest practical materials chemistry approaches for anticipating and managing bioavailable iron to minimize carbon nanotube toxicity.

Molecular cloning techniques are particularly well suited to the study of gene organization in Drasophila melanogaster because recombinant DNA can easily be localized in the genome by in situ hybridization to salivary gland polytene chromosomes. We report here the isolation and preliminary characterization of a recombinant phage, designated C25, containing a bona fide D. melanogaster ribosomal protein gene. In situ hybridization demonstrates that this sequence maps to region 99D on chromosome 3.

Asbestos fibers produce diffuse malignant mesotheliomas in chronic rodent inhalation assays or after direct intrapleural or intraperitoneal injection. In vitro models have provided evidence that asbestos fibers are genotoxic carcinogens that can directly or indirectly generate reactive oxygen- and nitrogen-derived species that cause DNA damage. Heterozygous p53+/- mice show an increased incidence and reduced latency of malignant mesotheliomas induced by weekly intraperitoneal injections of crocidolite asbestos fibers. In this study, we investigated whether loss of heterozygosity (LOH) at the p53 tumor-suppressor gene locus contributes to accelerated tumor progression. LOH was found in 50% of the tumors produced in heterozygous p53+/- mice. In contrast to tumors that arise in p53+/+ mice or those that retained one p53 allele, LOH was associated with large tumor masses with central areas of necrosis, local invasion, and penetration of lymphatics. Increased tumor size was not associated with increased levels of cell proliferation as determined by BrdU incorporation, but it was correlated with a reduction in apoptosis as determined morphologically and by the TUNEL assay. Wild-type p53 protein is essential for cell cycle arrest in response to DNA damage and in maintenance of genomic stability. Cell lines established from tumors that showed LOH at the p53 tumor-suppressor gene locus were nearly tetraploid. These results suggest that p53 haplo-insufficiency sensitizes mice to the clastogenic or aneuploidogenic effects of crocidolite asbestos fibers, resulting in a shorter latent period. As solid tumors develop, spontaneous loss of the wild-type allele accompanied by decreased apoptosis and genetic instability is associated with accelerated tumor growth, invasion, and lymphatic dissemination.

Different physiological conditions affect the biosynthesis and processing of hypophysiotropic proTRH in the hypothalamic paraventricular nucleus, and consequently the output of TRH. Early studies suggest that norepinephrine (NE) mediates the cold-induced activation of the hypothalamic-pituitary-thyroid axis at a central level. However, the specific role of NE on the biosynthesis and processing of proTRH has not been fully investigated. In this study, we found that NE affects gene transcription, protein biosynthesis, and secretion in TRH neurons in vitro; these changes were coupled with an up-regulation of prohormone convertase enzymes (PC) 1/3 and PC2. In vivo, NE is the main mediator of the cold-induced activation of the hypothalamic-pituitary-thyroid axis at the hypothalamic level, in which it potently stimulates the biosynthesis and proteolytic processing of proTRH through a coordinated up-regulation of the PCs. This activation occurs via beta-adrenoreceptors and phosphorylated cAMP response element binding signaling. In contrast, alpha-adrenoreceptors regulate TRH secretion but not proTRH biosynthesis and processing. Therefore, this study provides novel information on the molecular mechanisms of control of hypophysiotropic TRH biosynthesis.