Giant piezoresistive on/off ratios in rare-earth chalcogenide thin films enabling nanomechanical switching.

Sophisticated microelectromechanical systems for device and sensor applications have flourished in the past decade. These devices exploit piezoelectric, capacitive, and piezoresistive effects, and coupling between them. However, high-performance piezoresistivity (as defined by on/off ratio) has primarily been observed in macroscopic single crystals. In this Letter, we show for the first time that rare-earth monochalcogenides in thin film form can modulate a current by more than 1000 times due to a pressure-induced insulator to metal transition. Furthermore, films as thin as 8 nm show a piezoresistive response. The combination of high performance and scalability make these promising candidates for nanoscale applications, such as the recently proposed piezoelectronic transistor (PET). The PET would mechanically couple a piezoelectric thin film with a piezoresistive switching layer, potentially scaling to higher speeds and lower powers than today's complementary metal-oxide-semiconductor technology.

Mutations in host cell factor 1 separate its role in cell proliferation from recruitment of VP16 and LZIP.

Host cell factor 1 (HCF-1) is a nuclear protein required for progression through G(1) phase of the cell cycle and, via its association with VP16, transcriptional activation of the herpes simplex virus immediate-early genes. Both functions require a six-bladed beta-propeller domain encoded by residues 1 to 380 of HCF-1 as well as an additional amino-terminal region. The beta-propeller domain is well conserved in HCF homologues, consistent with a critical cellular function. To date, the only known cellular target of the beta-propeller is a bZIP transcription factor known as LZIP or Luman. Whether the interaction between HCF-1 and LZIP is required for cell proliferation remains to be determined. In this study, we used directed mutations to show that all six blades of the HCF-1 beta-propeller contribute to VP16-induced complex assembly, association with LZIP, and cell cycle progression. Although LZIP and VP16 share a common tetrapeptide HCF-binding motif, our results reveal profound differences in their interaction with HCF-1. Importantly, with several of the mutants we observe a poor correlation between the ability to associate with LZIP and promote cell proliferation in the context of the full HCF-1 amino terminus, arguing that the HCF-1 beta-propeller domain must target other cellular transcription factors in order to contribute to G(1) progression.

Exposure of neurons to excitotoxic levels of glutamate induces cleavage of the RNA editing enzyme, adenosine deaminase acting on RNA 2, and loss of GLUR2 editing.

AMPA receptors are glutamate receptors that are tetramers of various combinations of GluR1-4 subunits. AMPA receptors containing GluR1, 3 and 4 are Ca2+ permeable, however, AMPA receptors containing even a single subunit of GluR2 are Ca2+ impermeable. Most AMPA receptors are Ca2+ impermeable due to the presence of GluR2. GluR2 confers special properties on AMPA receptors through the presence of arginine at the pore apex; other subunits (GluR1, 3, 4) contain glutamine at the pore apex and allow Ca2+ influx. Normally, an RNA editing step changes DNA-encoded glutamine to arginine, introduces arginine in the GluR2 pore apex. GluR2 RNA editing is carried out by an RNA-dependent adenosine deaminase (ADAR2). Loss of GluR2 editing leads to the formation of highly excitotoxic AMPA channels [Mahajan and Ziff (2007) Mol Cell Neurosci 35:470-481] and is shown to contribute to loss of motor neurons in amyotrophic lateral sclerosis (ALS). Relatively higher levels of Ca2+-permeable AMPA receptors are found in motor neurons and this has been correlated with lower GluR2 mRNA levels. However, the reason for loss of GluR2 editing is not known. Here we show that exposure of neurons to excitotoxic levels of glutamate leads to specific cleavage of ADAR2 that leads to generation of unedited GluR2. We demonstrate that cleaved ADAR2 leads to a decrease or loss of GluR2 editing, which will further result in high Ca2+ influx and excitotoxic neuronal death.

Novel toxicity of the unedited GluR2 AMPA receptor subunit dependent on surface trafficking and increased Ca2+-permeability.

RNA editing modifies the GluR2 AMPA receptor subunit pore loop at the Q/R site and limits receptor Ca(2+) permeability. Editing failure is implicated in neurodegenerative diseases, including amyotrophic lateral sclerosis. We show that channels with unedited GluR2 are highly toxic in cultured hippocampal neurons. Toxicity exceeds that of other Ca(2+)-permeable AMPA receptor types and is influenced by agonist binding site mutations, ability to desensitize, and extracellular Ca(2+) levels. Significantly, toxicity also depends on GluR2's constitutive surface trafficking, a function dependent on GluR2 C-terminal domain interaction with NSF, a specialized chaperone. We have exploited the interaction between unedited GluR2 and NSF to reduce GluR2 surface levels. We show that a peptide that blocks the GluR2-NSF interaction reduces unedited GluR2 toxicity by reducing receptor surface expression. Peptide block of trafficking provides a model for design of drugs to reduce unedited GluR2 excitotoxicity in neurodegenerative diseases that result from editing failure.

Synergistic antimalarial activity of ketones with rufigallol and vitamin C.

Malaria remains a major cause of human morbidity and mortality worldwide. Plasmodium falciparum, the most virulent of the 4 human Plasmodium species causing malaria, is potentially life threatening, is increasing in prevalence and is becoming even more resistant to in-use drugs. In light of the growing problem of multi-drug resistance to malarial parasites, the development of new drugs or the use of a combination therapy is of primary importance. A previous report describes a remarkable synergistic antimalarial interaction between 2 structurally similar compounds, rufigallol, an anthraquinone derivative and exifone, a benzophenone derivative, in vitro. The synergistic antimalarial activity of exifone and vitamin C was also reported. To extend the same analogy to other ketones, we carried out antimalarial testing of 20 benzophenone derivatives, individually, in combination with rufigallol, and also in combination with vitamin C, in mice infected with Plasmodium berghei. Five ketones, out of 20, showed good antimalarial activity, in vivo, when tested individually. Nine ketones, out of 20, showed good antimalarial activity, in vivo, when tested in combination with rufigallol, indicating the synergism between them. However, synergism between ketones and vitamin C was not satisfactory since only 2 ketones showed good antimalarial activity when tested in combination with vitamin C.

Transcriptional activation of avian CYP1A4 and CYP1A5 by 2,3,7, 8-tetrachlorodibenzo-p-dioxin: differences in gene expression and regulation compared to mammalian CYP1A1 and CYP1A2.

The toxicity, carcinogenicity, and biochemical effects of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) are dependent upon activation of the Ah receptor, a ligand-activated transcription factor. Ah receptor activation leads to the induction of cytochrome P450 (CYP) 1A enzymes, which include CYP1A1 and 1A2 in mammals and CYP1A4 and 1A5 in chickens. CYP1A induction is a major effect of TCDD exposure although its relationship to TCDD toxicity and carcinogenicity are not understood. In these studies we investigated by nuclear run-on transcription assays along with Northern and Western blotting in chick embryo liver, kidney, and heart whether avian CYP1A4 and 1A5, like mammalian CYP1A1 and 1A2, are transcriptionally induced by TCDD and whether the chick CYP1A enzymes exhibit differences analogous to mammalian CYP1A enzymes in organ expression. We report that CYP1A4 and 1A5, like CYP1A1 and 1A2, are transcriptionally induced by TCDD in liver. However, whereas CYP1A1 is not constitutively expressed in liver, CYP1A2 and both CYP1A4 and 1A5 are constitutively expressed. Further, whereas TCDD induces only CYP1A1 and not CYP1A2 in extrahepatic organs, TCDD induces both CYP1A4 and 1A5 in chick kidney. Also, TCDD induced CYP1A4 but not 1A5 in both myocardium and heart vessels whereas CYP1A1 induction has only been found in endocardium. Further, liver CYP1A4 and 1A5 mRNAs had the same half lives and were both superinduced by cycloheximide, whereas mRNA half lives differ for CYP1A1 and 1A2, and cycloheximide superinduces only CYP1A1. We suggest that there are species differences in the effects of TCDD on CYP1A gene expression, organ distribution, and regulation that are likely to be accompanied by differences in CYP1A function and that this diversity may contribute to the large differences in sensitivity to TCDD among species.

Aroma compounds in sweet whey powder.

Aroma compounds in sweet whey powder were investigated in this study. Volatiles were isolated by solvent extraction followed by solvent-assisted flavor evaporation. Fractionation was used to separate acidic from nonacidic volatiles. Gas chromatography/mass spectrometry and gas chromatography/olfactometry were used for the identification of aroma compounds. Osme methodology was applied to assess the relative importance of each aroma compound. The most aroma-intense free fatty acids detected were acetic, propanoic, butanoic, hexanoic, heptanoic, octanoic, decanoic, dodecanoic, and 9-decenoic acids. The most aroma-intense nonacidic compounds detected were hexanal, heptanal, nonanal, phenylacetaldehyde, 1-octen-3-one, methional, 2,6-dimethylpyrazine, 2,5-dimethylpyrazine, 2,3-dimethylpyrazine, 2,3,5-trimethylpyrazine, furfuryl alcohol, p-cresol, 2-acetylpyrrole, maltol, furaneol, and several lactones. This study suggested that the aroma of whey powder could comprise compounds originating from milk, compounds generated by the starter culture during cheese making, and compounds formed during the manufacturing process of whey powder.

Herpes simplex virus transactivator VP16 discriminates between HCF-1 and a novel family member, HCF-2.

Herpes simplex virus infection is initiated by VP16, a viral transcription factor that activates the viral immediate-early (IE) genes. VP16 does not recognize the IE gene promoters directly but instead forms a multiprotein complex with Oct-1 and HCF-1, a ubiquitous nuclear protein required for progression through the G1 phase of the cell cycle. The functional significance of recruiting HCF-1 to the VP16-induced complex is not understood. Here we describe the identification of a second HCF-like protein, designated HCF-2. HCF-2 is smaller than HCF-1 but shares three regions of strong amino acid sequence homology, including the beta-propeller domain required for association with VP16. HCF-2 is expressed in many tissues, especially the testis, and shows a more dynamic pattern of subcellular localization than HCF-1. Although HCF-2 associates with VP16 and can support complex assembly with Oct-1 and DNA, it is significantly less efficient than HCF-1. A similar preference is shown by LZIP, a cellular counterpart of VP16. Analysis of chimeric proteins showed that differences between the fifth and sixth kelch repeats of the beta-propeller domains from HCF-1 and HCF-2 dictate this selectivity. These results reveal an unexpected level of specificity in the recruitment of HCF-1 to the VP16-induced complex, paralleling the preferential selection of Oct-1 rather than the closely related POU domain protein Oct-2. Implications for regulation of the viral life cycle are discussed.

Carboxy terminus of human herpesvirus 8 latency-associated nuclear antigen mediates dimerization, transcriptional repression, and targeting to nuclear bodies.

Human herpesvirus 8 (HHV-8; also known as Kaposi's sarcoma-associated herpesvirus) is the causative agent of Kaposi's sarcoma and certain B-cell lymphomas. In most infected cells, HHV-8 establishes a latent infection characterized by the expression of latency-associated nuclear antigen (LANA) encoded by open reading frame 73. Although unrelated by sequence, there are functional similarities between LANA and the EBNA-1 protein of Epstein-Barr virus. Both accumulate as subnuclear speckles and are required for maintenance of the viral episome. EBNA-1 also regulates viral gene expression and is required for cell immortalization, suggesting that LANA performs similar functions in the context of HHV-8 infection. Here we show that LANA forms stable dimers, or possibly higher-order multimers, and that this is mediated by a conserved region in the C terminus. By expressing a series of truncations, we show that both the N- and C-terminal regions localize to the nucleus, although only the C terminus accumulates as nuclear speckles characteristic of the intact protein. Lastly, we show that LANA can function as a potent transcriptional repressor when tethered to constitutively active promoters via a heterologous DNA-binding domain. Domains in both the N and C termini mediate repression. This suggests that one function of LANA is to suppress the expression of the viral lytic genes or cellular genes involved in the antiviral response.

The development and psychometric evaluation of the Motivation and Energy Inventory (MEI).

Because depressed patients commonly experience reductions in motivation and energy, both as symptoms of their disorder and as side effects of pharmacotherapy, it is important to identify interventions that can restore their vitality. The Motivation and Energy Inventory (MEI) was recently developed to facilitate the evaluation of such efforts both in depression research, as well as in other therapeutic areas where vitality is an important issue. The constructs addressed by the MEI were identified through a combination of literature review, consultation with experts, and patient focus groups. Potential problems identified during cognitive testing and addressed in subsequent revisions related to the instructions, reference period, response scale sizes, and response scale labels, as well as a number of item-specific issues. Most recently, the data from two randomized, placebo-controlled clinical trials were utilized to evaluate the psychometric properties of the new questionnaire. In general, the data collected during the first and second trial were used for exploratory and confirmatory analysis, respectively. Consistent with the measurement model of the MEI, the psychometric results confirm that the instrument has three factors generally addressing physical energy, mental energy, and social motivation. Furthermore, these results provide evidence for the internal consistency, construct validity, and responsiveness of all three MEI subscales. Additional work is currently underway to examine test-retest reliability and establish minimal clinically important difference values for the MEI subscales.