bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of Gas Hydrate Formation Using Surfactant Systems: Underlying Concepts and New Applications
Authors: IRVIN GLEN , LI SICHU , SIMMONS BLAKE , JOHN VIJAY , McPHERSON GARY , MAX MICHAEL , PELLENBARG ROBERT
Published: July 2010

Abstract: We describe some new approaches to the rapid formation of gas hydrates using surfactant systems that form reverse micelles. The thermodynamics of hydrate formation in surfactant containing reverse micellar systems indicate the possibility of controlling hydrate deposition. The use of reverse micellar systems also allows the deposition of hydrates in the form of small crystallites that do not aggregate. Surfactants also appear to displace agglomerated hydrates from surfaces, thereby facilitating flow. Direct injection of water into gas saturated liquid hydrocarbons leads to rapid hydrate formation. On the other hand, water droplets injected into liquid carbon dioxide indicate a gradual conversion to the hydrate form with the initial formation of a hydrate skin. An interesting application of rapid hydrate formation is its use in the restriction of inorganic nanocluster growth.
Kinetics of Ethane Hydrate Growth on Latex Spheres Measured by a Light Scattering Technique
Authors: SERVIO PHILLIP , ENGLEZOS PETER , BISHNOI P. RAJ
Published: July 2010

Abstract: A high pressure, temperature‐controlled sapphire equilibrium cell is used to observe the nucleation and growth behavior of gas hydrates in bulk water or on spheres suspended in water. Gas hydrate crystals are grown on positively and negatively charged latex spheres. The experiments have been conducted on an ethane‐water system that is known to form structure I hydrate. Experiments were carried out at temperatures between 278.0 K and 278.6 K and pressures ranging from 1,300 kPa to 1,500 kPa. A light scattering apparatus was used to monitor the hydrate formation process. In particular, the photomultiplier voltage was recorded over time in order to observe the effects of latex spheres on the nucleation and growth of gas hydrates. More experiments need to be performed to better ascertain the hydrate nucleation and growth behavior in the presence of latex spheres.
Molecular Dynamics Simulations of Clathrate Hydrate: Intramolecular Vibrations of Methane
Authors: ITOH HIDENOSUKE , KAWAMURA KATSUYUKI
Published: July 2010

Abstract: Intramolecular vibrational spectra of methane in clathrate hydrate structure I were obtained by molecular dynamics simulations using the Kumagai, Kawamura, and Yokokawa (KKY) potential model that allows unconstrained atomic motions. Peak frequency shifts between the power spectra of methane molecules in large and small cages were found in the GH stretching (υl, υ3) modes, in contrast no frequency shifts were observed in the H‐C‐H bending (υ2, υ4) modes. We discuss an interaction between water and methane molecules from these frequency shifts and the GH distance depending on the cage size. An understanding of the interaction between guest and host molecules helps us to clarify the formation and dissociation processes of clathrate hydrates.
The Application of Raman Spectroscopy to the Study of Gas Hydrates
Authors: TULK C. A. , RIPMEESTER J. A. , KLUG D. D.
Published: July 2010

Abstract: Raman spectroscopy is reviewed with particular emphasis placed on its application to gas hydrates. Experimental examples discussed include studies of the totally symmetric C‐H stretching vibration ν1 (A1) of methane in both synthetic and natural hydrate samples (from the JAPEX/JNOC/GSC Mallik 2L‐38 research well); a comparison of the coupled O‐H vibrations of water in the host lattice of CH4 hydrate and ice Ih at low temperature; and local structural details of the relaxation of the hydrogen‐bonded water on crystallization to structure II hydrate of amorphous tetrahydrofuran (THF) aqueous solutions. This paper is intended to be an introduction to Raman spectroscopy with specific examples from research at the National Research Council of Canada, and is aimed at those who wish to apply the technique as a tool to investigate gas hydrates.
Formation of Natural Gas Hydrates in Marine Sediments: Gas Hydrate Growth and Stability Conditioned by Host Sediment Properties
Authors: CLENNELL M. BEN , HENRY PIERRE , HOVLAND MARTIN , BOOTH JAMES S. , WINTERS WILLIAM J. , THOMAS MICHEL
Published: July 2010

Abstract: The stability conditions of submarine gas hydrates (methane clathrates) are largely dictated by pressure, temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of the host sediments also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our model presumes that gas hydrate behaves in a way analogous to ice in the pores of a freezing soil, where capillary forces influence the energy balance. Hydrate growth is inhibited within fine‐grained sediments because of the excess internal phase pressure of small crystals with high surface curvature that coexist with liquid water in small pores. Therefore, the base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature, and so nearer to the seabed than would be calculated from bulk thermodynamic equilibrium. The growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, sheets, and lenses in muds; cements in sand and ash layers) can be explained by a requirement to minimize the excess of mechanical and surface energy in the system.
Improving the Accuracy of Gas Hydrate Dissociation Point Measurements
Authors: TOHIDI B. , BURGASS R. W. , DANESH A. , ØSTERGAARD K. K. , TODD A. C.
Published: July 2010

Abstract: Following our previous communications on the impact of the amount of water phase on the time required at each temperature‐step 1 and the limitations of visual techniques in determining hydrate dissociation points, 2 a series of tests were conducted in this laboratory to investigate the impact of measuring techniques, mixing efficiency, heating method and heating rate on the accuracy of hydrate dissociation point measurements. The results showed that nonvisual techniques combined with stepwise heating and satisfactory mixing could save a significant amount of time while providing accurate hydrate dissociation data.
Dissociation of Natural Gas Hydrates Observed by X‐ray CT Scanner
Authors: MIKAMI JUN , MASUDA YOSHIHIRO , UCHIDA TAKASHI , SATOH TOHRU , TAKEDA HIDEAKI
Published: July 2010

Abstract: Core samples containing pore‐space gas hydrate within granular sands were collected from 913.76 m of the research well named JAPEX/JNOC/GSC Mallik 2L‐38. X‐ray CT images of the core were acquired while warming from −18 to 4°C, and subsequently during stepped decreases of 0.1 MPa in the chamber pressure below the methane hydrate equilibrium pressure. Discharged gas flows and sample temperatures were monitored continuously. Changes in CT values indicated that gas hydrate dissociated simultaneously both on the exposed surfaces and within the pore spaces of the sample in response to pressure changes. This suggested that pressure reductions were effectively transmitted through the sample most likely because the samples contained some amount of fluids. The result of gas flow measurements indicated that a larger pressure drawdown caused a higher dissociation rate.
Hydrate Phase Composition for Multicomponent Gas Mixtures
Authors: NG HENG‐JOO
Published: July 2010

Abstract: This investigation was carried out to determine the composition of guest components in the equilibrium hydrate phase. Measurements were made for six gas mixtures containing methane, ethane, propane, iso‐butane, n‐butane, and carbon dioxide. Gas hydrate was formed in the presence of water at two pressures, 2.07 and 6.89 MPa, and at temperatures 28°C below the corresponding equilibrium hydrate temperature. The results obtained showed that, with some exceptions, the van der Waals‐Platteeuw thermodynamic model can be used for hydrate phase composition calculations.
Development of Human Cell Lines from Multiple Organs
Authors: RHIM JOHNG S.
Published: July 2010

Abstract: While the majority of carcinogenesis studies have relied on the use of rodent cells in culture, experimental models to define the role of carcinogenic agents in the development of cancers must be established by using a variety of human cells. Unlike rodent cells, normal human cells in culture rarely undergo spontaneous transformation and have generally proven to be resistant to neoplastic transformation by carcinogens. Remarkable progress has been made during the past decade in human cell transformation systems. Malignant transformation of human cells in culture has been achieved by a stepwise process: immortalization and conversion of the immortalized cells to tumorigenic cells. One of the critical initial events in the progression of normal human cells to tumor cells is the escape from cellular senescence, with few exceptions; normal human cells require immortalization to provide a practical system for carcinogenesis studies. Different cell types require different conditions and transforming agents to achieve a useful cell line. The current state of the art in immortalization of human cells will be presented.
Fluorometric High‐Throughput Screening for Inhibitors of Cytochrome P450
Authors: MILLER VAUGHN P. , STRESSER DAVID M. , BLANCHARD ANDREW P. , TURNER STEPHANIE , CRESPI CHARLES L.
Published: July 2010

Abstract:Rapid screening for cytochrome P450 inhibitors is part of the current paradigm for avoiding development of drugs likely to give clinical pharmacokinetic drug‐drug interactions and associated toxicities. We have developed microtiter plate‐based, direct, fluorometric assays for the activities of the principal human drug‐metabolizing enzymes, CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, as well as for CYP2A6, which is an important enzyme in environmental toxicology. These assays are rapid and compatible with existing high‐throughput assay instrumentation. For CYP1A2, CYP2C8, CYP2C9, CYP2C19, and CYP2D6, the potency of enzyme inhibition (IC50) is consistent regardless of the probe substrate or assay method employed. In contrast, CYP3A4 inhibition for an individual inhibitor shows significant differences in potency (>300‐fold) depending on the probe substrate being used. We have investigated these differences through the use of several structurally distinct fluorescent substrates for CYP3A4 and several classical substrate probes (e.g., testosterone, nifedipine, and midazolam), with a panel of known, clinically significant, CYP3A4 inhibitors. The use of multiple probe substrates appears to be needed to characterize the inhibition potential of xenobiotics for CYP3A4.
Quantitative Proteome Analysis: Methods and Applications
Authors: AEBERSOLD RUEDI , RIST BEATE , GYGI STEVEN P.
Published: July 2010

Abstract: With the completion of a rapidly increasing number of complete genomic sequences, much attention is currently focused on how the information contained in sequence databases might be interpreted in terms of the structure, function, and control of biological systems. Quantitative proteome analysis, the global analysis of protein expression, has been proposed as a method to study steady‐state gene expression and perturbation‐induced changes. Here, we discuss the rationale for quantitative proteome analysis, highlight the limitations in the current standard technology, and introduce a new experimental approach to quantitative proteome analysis.
Pharmaceutical Proteomics
Authors: STEINER SANDRA , ANDERSON N. LEIGH
Published: July 2010

Abstract: Genomics and proteomics are today well established in drug discovery and, in combination with combinatorial chemistry and high‐throughput screening, are helping to bring forward an unprecedented number of potential lead compounds. To avoid the generation of bottlenecks downstream in drug development, increasing pressure is arising to integrate these technologies into the development environment. Proteomics has demonstrated proof‐of‐concept in toxicology as shown by a number of successful applications in mechanistic toxicology and lead selection. The “technology wave” is now starting to impact the clinical phase of drug development. Expected benefits are optimized clinical trials based on the availability of biologically relevant markers of drug efficacy and safety.
Gene Expression Microarray Data Analysis for Toxicology Profiling
Authors: CUNNINGHAM M. J. , LIANG S. , FURMAN S. , SEILHAMER J. J. , SOMOGYI R.
Published: July 2010

Abstract:When dealing with thousands of genes, all potentially interesting, it is desirable to rank the genes according to their degree of participation in a physiological process. Therefore, genes with the highest Shannon entropy and ERL can be selected as the best toxicity target candidates, permitting preclinical scientists to focus their research and resources on those genes.
p53 Tumor Suppressor Gene: At the Crossroads of Molecular Carcinogenesis, Molecular Epidemiology, and Human Risk Assessment
Authors: HUSSAIN S. PERWEZ , HOLLSTEIN MONICA H. , HARRIS CURTIS C.
Published: July 2010

Abstract: The molecular archaeology of the mutation spectra of tumor suppressor genes generates hypotheses concerning the etiology and molecular pathogenesis of human cancer. The spectrum of somatic mutations in the p53 gene implicates environmental carcinogens and both endogenous agents and processes in the etiology of human cancer.
Mechanisms of Cell Transformation in the Syrian Hamster Embryo (SHE) Cell Transformation System
Authors: ISFORT ROBERT J.
Published: July 2010

Abstract:The Syrian hamster embryo (SHE) cell transformation system has been used for investigational studies of basic mechanisms of neoplastic transformation, as well as determining the carcinogenic potential of chemical, physical, and biological agents. Many of these investigations utilize an intermediate step in the SHE cell neoplastic transformation process, known as morphological transformation, as an indicator that the cells have acquired an increased potential to progress to malignancy. While the nature of the morphologically transformed phenotype is not completely understood, it is believed to result from a block in the cellular differentiation of stem cells present within the SHE cell population. In terms of determination of the transforming potential of biological/chemical/physical agents, more than 500 agents have been tested in the SHE cell transformation assay with an 80–90% correlation between MT and carcinogenic potential. As such, the SHE cell transformation assay has utility as a test to provide short‐term information on the carcinogenic potential of chemicals. One class of agents of current interest with regard to SHE cell transformation assay utilization consists of growth and differentiation factors (GDFs). Analysis of the SHE cell transformation potential of the GDFs, epidermal growth factor (EGF), fibroblast growth factor 4 (FGF‐4), platelet‐derived growth factor AA (PDGF AA), PDGF AB, PDGF BB, and the antimitogenic GDF, transforming growth factor beta one (TGF‐β1), was performed. All GDFs, with the exception of TGF‐β1, induced SHE cell transformation. However, an interesting difference between the GDFs was observed‐PDGF A/B and PDGF B/B, but not PDGF A/A, EGF, or FGF‐4, induced transformation after both a transient 1‐day exposure and a continuous 7‐day exposure, while continuous 7‐day exposure was required for transformation by PDGF A/A, EGF, and FGF‐4. interestingly, both transient 1‐day and continuous 7‐day TGF‐β1 exposure resulted in suppression of transformation induced by a variety of transforming agents including growth factors, Ames assay‐positive carcinogens, Ames assay‐negative carcinogens, and spontaneous transformation. Interestingly TGF‐β1 was not able to suppress transformation by the tumor promoter, TPA. Together, these data demonstrate the utility of the Syrian hamster embryo cell transformation system for analyzing the transforming potential of GDFs and for characterizing differences in transforming mechanisms between different GDFs.
In Vitro Systems as Simulations of In Vivo Conditions: The Study of Cognition and Synaptic Plasticity in Neurotoxicologya
Authors: GILBERT M. E.
Published: July 2010

Abstract: Neuroscientists have been engaged for decades in the search for brain regions and brain processes that underlie learning and memory. The effects of regional brain stimulation and ablation on behavior have been documented and inferences made on the impact of these manipulations on the psychological constructs of “learning” and “memory”. Discovery of an electrophysiological property, long‐term potentiation (LTP), greatly expanded the ability to probe cellular aspects of how memories are represented in the brain. The study of LTP serves as an excellent example of how in vivo phenomena can be taken to more simplified in vitro test systems to directly address cellular and biochemical mechanisms of information storage in brain.
In Vitro Percutaneous Absorption Models
Authors: BRONAUGH ROBERT L.
Published: July 2010

Abstract: In vitro skin absorption studies are commonly used to estimate in vivo skin absorption in topical safety and efficacy evaluations. in vitro studies are more economical and result in minimization or elimination of the use of animals.
Aging and Resistance toTrichinella spiralisInfection following Xenobiotic Exposure
Authors: LUEBKE ROBERT W. , COPELAND CAREY B. , ANDREWS DEBORA L.
Published: July 2010

Abstract:Aging is accompanied by well‐documented physiological changes, including alterations in the immune system that can lead to reduced resistance to a variety of infectious agents. We tested the hypothesis that immunosenescence exacerbates the immunosuppressive effect of xenobiotics. If proven true, a given dose of an immunosuppressive xenobiotic would cause greater suppression of host resistance in an aged population.
Animal Models to Assess the Effects of Air Pollutants on Allergic Lung Disease
Authors: SELGRADE MARYJANE K. , LAMBERT AMY L. , WARD MARSHA D. W. , GILMOUR M. IAN
Published: July 2010

Abstract: Animal models provide toxicologists with useful tools for assessing risks associated with respiratory allergy. Both the mouse and BN rat models described exhibit many of the features of human allergic asthma. It is clear that environmental contaminants can exacerbate the expression of these features. Work is under way to explore underlying mechanisms and to develop methods for applying these data to human health risk assessment.
Genetic Basis of Susceptibility to Environmentally Induced Neural Tube Defects
Authors: FINNELL RICHARD H. , GELINEAU‐VAN WAES JANEE , BENNETT GREGORY D. , BARBER ROBERT C. , WLODARCZYK BOGDAN , SHAW GARY M. , LAMMER EDWARD J. , PIEDRAHITA JORGE A. , EBERWINE JAMES H.
Published: July 2010

Abstract:Neural tube defects (NTDs) are among the most common of all human congenital defects, with multifactorial etiologies comprising both environmental and genetic components. Several murine model systems have been developed in an effort to elucidate genetic factors regulating expression of NTDs. Strain‐dependent differences in susceptibility to teratogenic insults and altered patterns of gene expression observed within the neuroepithelium of affected embryos support the hypothesis that subtle genetic changes can result in NTDs. Since several affected genes are folate‐regulated, transgenic knockout mice lacking a functional folate receptor were developed. Nullizygous embryos diedin uterowith significant morphological defects, supporting the critical role of folic acid in early embryogenesis. While epidemiological studies have not established an association between polymorphisms in the human folate receptor gene and NTDs, it is known that folate supplementation reduces infant NTD risk. Continued efforts are therefore necessary to reveal the mechanism by which folate works and the nature of the gene(s) responsible for human NTDs.
The α‐Synucleinopathies: Parkinson's Disease, Dementia with Lewy Bodies, and Multiple System Atrophy
Authors: SPILLANTINI MARIA GRAZIA , GOEDERT MICHEL
Published: July 2010

Abstract:Parkinson's disease is the second most common neurodegenerative disease, after Alzheimer's disease. Neuropathologically, it is characterized by the degeneration of populations of nerve cells that develop filamentous inclusions in the form of Lewy bodies and Lewy neurites. Recent work has shown that the filamentous inclusions of Parkinson's disease are made of the protein α‐synuclein and that rare, familial forms of Parkinson's disease are caused by missense mutations in the α‐synuclein gene. Besides Parkinson's disease, the filamentous inclusions of two additional neurodegenerative diseases, namely, dementia with Lewy bodies and multiple system atrophy, have also been found to be made of α‐synuclein. Recombinant α‐synuclein has been shown to assemble into filaments with similar morphologies to those found in the human diseases and with a cross‐β fiber diffraction pattern. The new work has established the α‐synucleinopathies as a major class of neurodegenerative disease.
Molecular Genetics of Chromosome 17 Tauopathies
Authors: HUTTON MICHAEL
Published: July 2010

Abstract: The identification of mutations in the gene encoding the micro‐tubule associated protein tau in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP‐17) demonstrated that tau dysfunction can lead to neurodegeneration. At least 11 missense mutations and 1 deletion mutation (ΔK280) have been identified in exons 9–13 that encode the microtubule binding domains of tau. In addition, five mutations have been found close to the 5′ splice site of exon 10. The different FTDP‐17 mutations have multiple effects on the biology and function of tau. These varied pathogenic mechanisms likely explain the wide range of clinical and neuropathological features observed in different families with FTDP‐17. In addition to the highly penetrant mutations that are found in large families with FTDP‐17, a common extended haplotype in the tau gene also appears to be a risk factor in the development of the apparently sporadic tauopathy, progressive supranuclear palsy (PSP). The mechanism by which this common variability in the tau gene influences the development of PSP is unclear; however, it further suggests a central role for tau in the pathogenesis of several neurodegenerative conditions including Alzheimer's disease (AD).
Tau Gene Mutations in Frontotemporal Dementia and Parkinsonism Linked to Chromosome 17 (FTDP‐17): Their Relevance for Understanding the Neurogenerative Process
Authors: GOEDERT MICHEL , GHETTI BERNARDINO , SPILLANTINI MARIA GRAZIA
Published: July 2010

Abstract: Tau is a microtubule‐associated protein that binds to microtubules and promotes microtubule assembly. Six tau isoforms are produced in adult human brain by alternative mRNA splicing from a single gene. Inclusion of a 31 amino acid repeat encoded by exon 10 of the tau gene gives rise to the three isoforms with four microtubule‐binding repeats each. The other three tau isoforms have three repeats each. Abundant neurofibrillary lesions made of tau protein constitute a defining neuropathological characteristic of Alzheimer's disease. Filamentous tau protein deposits are also the defining characteristic of other neurodegenerative diseases, many of which are frontotemporal dementias or movement disorders, such as Pick's disease, progressive supranuclear palsy, and corticobasal degeneration. It is well established that the distribution of tau pathology correlates with the presence of symptoms of disease. However, until recently, there was no genetic evidence linking tau to neurodegeneration. This has now changed with the discovery of more than 15 mutations in the tau gene in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP‐17). The new work has shown that dysfunction of tau protein causes neurodegeneration.
High Frequency of Mutations in Four Different Disease Genes in Early‐Onset Dementia
Authors: FINCKH ULRICH , MÜLLER‐THOMSEN TOMAS , MANN ULRIKE , EGGERS CHRISTIAN , MARKSTEINER JOSEF , MEINS WOLFGANG , BINETTI GIULIANO , ALBERICI ANTONELLA , SONDEREGGER PETER , HOCK CHRISTOPH , NITSCH ROGER M. , GAL ANDREAS
Published: July 2010

Abstract: Heterozygous mutations in the genes for amyloid precursor protein (APP), the presenilins (PS1, PS2), prion protein (PrP), neuroserpin, and tau are associated with early‐onset dementia (EOD) with or without neurological signs in the early disease stage. To investigate the proportion of EOD without early neurological signs attributable to known genes we prospectively (i.e., ante mortem) screened these six genes for mutations in 36 patients with EOD before age 60. Family history for dementia was positive (PFH) in 16, negative (NFH) in 17, and unknown (UFH) in 3 patients. In 12 patients, we found 5 novel mutations (PS1: F105L; PS2: T122P, M239I; PrP: Q160X, T188K) and 5 previously reported mutations (APP: in three most likely unrelated patients V717I; PS1: A79V, M139V; PrP: P102L, T183A) that all are considered disease causing. Of these 12 patients, 9 had PFH. This indicates a detection rate of 56% (9/16) in patients with PFH. We found 2 mutations (APP V717I) in 2 of the 3 the UFH‐patients, and only 1 mutation (PrP T188K) in 1 of the 17 patients with NFH. No mutation was found in tau and neuroserpin genes. To date, three patients died and FAD, predicted by PS mutations in two patients, and prion disease, predicted by a PrP mutation in the third one, were histopathologically confirmed at autopsy. Up to now, mutation findings may be the most specific biomarkers for an ante mortem diagnosis of FAD or hereditary prion disease.
Rapid Notch1 Nuclear Translocation after Ligand Binding Depends on Presenilin‐associated γ‐Secretase Activity
Authors: BEREZOVSKA OKSANA , JACK CHRISTINE , McLEAN PAMELA , ASTER JON C. , HICKS CAROL , XIA WEIMING , WOLFE MICHAEL S. , WEINMASTER GERRY , SELKOE DENNIS J. , HYMAN BRADLEY T.
Published: July 2010

Abstract: Recent data suggest an intimate relationship between the familial Alzheimer disease gene presenilin 1 (PS1) and proteolytic processing of both the amyloid precursor protein (APP) and the important cell signaling molecule, Notch1. We now show, using mammalian cells transfected with full‐length Notch1, that the C terminal domain of Notch1 rapidly translocates to the nucleus upon stimulation with the physiologic ligand Delta and initiates a CBF1‐dependent signal transduction cascade. Using this assay, we demonstrate that the same aspartate mutations in PS1 that block APP processing also prevent Notch1 cleavage and translocation to the nucleus. Moreover, we show that two APP γ‐secretase inhibitors also diminish Notch1 nuclear translocation in a dose‐dependent fashion. However, Notch1 signaling, assessed by measuring the activity of CBF1, a downstream gene, was reduced but not completely abolished in the presence of either aspartate mutations or γ‐secretase inhibitors. Our results support the hypothesis that similar PS1‐related enzymatic activity is necessary for both APP and Notch1 processing, yet suggest that Notch signaling may remain relatively preserved with moderate levels of γ‐secretase inhibition.
Overexpression of Presenilin‐2 Enhances Apoptotic Death of Cultured Cortical Neurons
Authors: ARAKI W. , YUASA K. , TAKEDA S. , SHIROTANI K. , TAKAHASHI K. , TABIRA T.
Published: July 2010

Abstract: Presenilin‐2 (PS2) is a gene of unknown function linked with some forms of familial Alzheimer's disease. To investigate the biological role of PS2 in neurons, we overexpressed PS2 in primary cortical neurons using recombinant adenoviral vectors. Western blot and immunohistochemical analyses showed enhanced expression of PS2 proteins in infected neurons after infection of recombinant adenoviruses containing the human wild‐type or mutant PS2 gene. Neuronal survival was decreased by approximately 30% in cultures infected with adenovirus expressing either wild‐type or mutant PS2, as compared with those infected with adenovirus expressing the LacZ gene. Fragmented nuclei were frequently observed in dying neurons. These data suggest that apoptotic death of cultured cortical neurons is enhanced by PS2 over‐expression.
Treatment with the Selective Muscarinic Agonist Talsaclidine Decreases Cerebrospinal Fluid Levels of Total Amyloid β‐Peptide in Patients with Alzheimer's Disease
Authors: HOCK C. , MADDALENA A. , HEUSER I. , NABER D. , OERTEL W. , VON DER KAMMER H. , WIENRICH M. , RASCHIG A. , DENG M. , GROWDON J. H. , NITSCH R. M.
Published: July 2010

Abstract: Brain amyloid load in Alzheimer's disease (AD) is, at least in genetic forms, associated with overproduction of amyloid β‐peptides (Aβ). Thus, lowering Aβ production is a central therapeutic target in AD and may be achieved by modulating such key enzymes of amyloid precursor protein (APP) processing as β‐, γ‐, and α‐secretase activities. Talsaclidine is a selective muscarinic M1 agonist that stimulates the nonamyloidogenic α‐secretase pathway in model systems. Talsaclidine was administered double‐blind, placebo‐controlled, and randomized to 24 AD patients and cerebrospinal fluid (CSF) levels of total Aβ were quantitated before and after 4 weeks of drug treatment. We observed that talsaclidine decreases CSF levels of Aβ significantly over time within the treatment group (n=20) by a median of 16% as well as compared to placebo (n=4) by a median of 27%. We conclude that treatment with selective M1 agonists may reduce Aβ production and may thus be further evaluated as a potential amyloid‐lowering therapy of AD.
M1 Muscarinic Agonists as Potential Disease‐Modifying Agents in Alzheimer's Disease: Rationale and Perspectives
Authors: FISHER A. , MICHAELSON D.M. , BRANDEIS R. , HARING R. , CHAPMAN S. , PITTEL Z.
Published: July 2010

Abstract: A cholinergic hypofunction in Alzheimer's disease (AD) may lead to formation of β‐amyloids that might impair the coupling of M1 muscarinic ACh receptors (mAChRs) with G proteins. This disruption in coupling can lead to decreased signal transduction, to a reduction in levels of trophic amyloid precursor proteins (APPs), and to generation of more β‐amyloids that can also suppress ACh synthesis and release, aggravating further the cholinergic deficiency. These “vicious cycles,” a presynaptic and a postsynaptic one, may be inhibited, in principle, by M1 selective agonists. Such properties can be detected in the functionally selective M1 agonists from the AF series [e.g., project drugs, AF102B, AF150(S)]. These M1 agonists promote the nonamyloidogenic APP processing pathways and decrease tau protein phosphorylation. The effects on tau proteins suggest a link between M1 mAChR‐mediated signal transduction system(s) and the neuronal cytoskeleton via regulation of phosphorylation of tau microtubule‐associated protein. This may indicate a dual role for M1 agonists: as inhibitors of two “vicious cycles,” one induced by β‐amyloids, and the other due to overactivation of certain kinases (e.g., glycogen synthase kinase‐3, GSK‐3) or downregulation of phosphatases, respectively. Prolonged administration of AF150(S) in apolipoprotein E‐knockout mice restored cognitive impairments, cholinergic hypofunction, and tau hyperphosphorylation, and unveiled a high‐affinity binding site to M1 mAChRs. Except M1 agonists, there are no reports of compounds having such combined effects, for example, amelioration of cognition dysfunction and beneficial modulation of APPs together with tau phosphorylation. This unique property of M1 agonists to alter different aspects of AD pathogenesis could represent the most remarkable, yet unexplored, clinical value of such compounds.
Cholinesterase Inhibitors Stabilize Alzheimer's Disease
Authors: GIACOBINI EZIO
Published: July 2010

Abstract: During the last decade, a systematic effort to develop a pharmacological treatment for Alzheimer disease (AD) has resulted into three drugs being registered for the first time in the USA and Europe for this specific indication. All three are cholinesterase inhibitors (ChEI). The major therapeutic effect of ChEI on AD patients is to maintain cognitive function at a constant level during a six‐month to one‐year period of treatment, as compared to placebo. Additional drug effects might slow cognitive deterioration and improve behavioral and daily living conditions. Comparison of clinical effects of six ChEI demonstrates a rather similar magnitude of improvement in cognitive measures. For some drugs, this may represent an upper limit, whereas for other it may still be possible to further increase the benefit. In order to maximize and prolong positive drug effects, it is important to start early and adjust dosage during the treatment. Recent studies show that in many patients the stabilization effect produced by ChEI can be prolonged for as long as a 24‐month period. In order to explain the stabilizing effect of ChEI, a mechanism other than AChE inhibition, based on β‐amyloid metabolism, is postulated.
In Vitro Evaluation of VIP/PACAP Receptors in Healthy and Diseased Human Tissues: Clinical Implications
Authors: REUBI JEAN CLAUDE
Published: July 2010

Abstract: The evaluation of peptide receptors in man is relevant to identifying the physiological target tissues of a given peptide and to selecting diseases with a sufficient receptor overexpression for diagnostic or therapeutic intervention. VIP/PACAP receptors have been evaluated in normal and diseased human non‐neuronal tissues by using in vitro receptor autoradiography with 125I‐VIP or 125I‐PACAP in tissue sections. As assessed by subtype‐selective VIP analogs, VIP receptors of the VPAC1 subtype are found in a wide variety of tissues including liver, breast, kidney, prostate, ureter, bladder, pancreatic ducts, gastrointestinal mucosa, lung, thyroid, adipose, and lymphoid tissues. VPAC2 receptors are predominantly found in vessels and smooth muscles, whereas PAC1 receptors are present in the adrenal medulla. VIP/PACAP receptors are expressed in the majority of the most frequently occurring human tumors, including breast, prostate, pancreas, lung, colon, stomach, liver, and bladder carcinomas, as well as lymphomas and meningiomas, predominantly as VPAC1 receptors, as do their tissues of origin. Although leiomyomas predominantly express VPAC2 receptors, glial tumors, pituitary adenomas, neuroblastomas, paragangliomas, pheochromocytomas, and endometrial carcinomas preferentially express PAC1 receptors. The very wide distribution of VIP/PACAP receptors in the normal human body is indicative of the key role of these peptides in human physiology and pathophysiology. Moreover, the receptor expression in tumors is the molecular basis for clinical applications of VIP/PACAP such as in vivo scintigraphy and radiotherapy of tumors as well as VIP/PACAP analog treatment for tumor growth inhibition.
VIP and PACAP Induce Shift to a Th2 Response by Upregulating B7.2 Expression
Authors: DELGADO MARIO , LECETA JAVIER , SUN WEI , GOMARIZ ROSA P. , GANEA DOINA
Published: July 2010

Abstract: VIP and PACAP, two structurally related neuropeptides produced within the lymphoid microenvironment, modulate several immunological functions. Although primarily anti‐inflammatory in nature, VIP and PACAP also affect resting macrophages. In this study, we report on the role of VIP and PACAP on macrophage B7 expression and costimulatory function for antigen‐primed CD4+ T cells, and on the macrophage‐induced regulation of Th1/Th2 differentiation in vitro and in vivo. VIP and PACAP upregulate B7.2, but not B7.1, MHC class II, or ICAM‐1 expression, and activate macrophages to stimulate the proliferation of naïve T cells in response to soluble anti‐CD3 or allogeneic stimulation. The stimulatory effect is mediated through the specific receptor VPAC1, and involves the cAMP/PKA pathway as second messengers. The enhancement in B7.2 expression occurs at both mRNA and protein levels, and correlates with the VIP/PACAP induced upregulation of the costimulatory activity of macrophages for antigen‐primed CD4+ T cells. VIP/PACAP‐treated macrophages gain the ability to induce Th2‐type cytokines such as IL‐4 and IL‐5, and to reduce Th1‐type cytokines such as IFNγ and IL‐2. In vivo administration of VIP or PACAP in antigen‐immunized mice reduces the numbers of IFNγ‐secreting cells, enhances the numbers of IL‐4‐secreting cells, and affects the pattern of antigen‐specific Ig isotypes. The preferential differentiation into Th2 effector cells induced by VIP/PACAP‐treated macrophages is mediated through the upregulation of B7.2 expression. Since Th1‐dominated responses are associated with some autoimmune diseases and inflammatory reactions typical of cell‐mediated immunity, the VIP/PACAP inhibition of Th1 development may represent an additional mechanism for the general anti‐inflammatory activity of the two neuropeptides.
A Novel VIP Responsive Gene: Activity Dependent Neuroprotective Protein
Authors: GOZES I. , ZAMOSTIANO R. , PINHASOV A. , BASSAN M. , GILADI E. , STEINGART R. A. , BRENNEMAN D. E.
Published: July 2010

Abstract:Activity dependent neuroprotective protein (ADNP, 828 amino acids, pI 5.99) is a glial‐derived protein that contains a femtomolar active neuroprotective peptide, NAPVSIPQ (NAP). VIP induces a two‐ to threefold increase in ADNP mRNA in astrocytes, suggesting that ADNP is a VIP‐responsive gene. ADNP is widely distributed in the mouse hippocampus, cerebellum, and cerebral cortex. VIP has been shown to possess neuroprotective activity that may be exerted through the activation of glial proteins. We suggest that ADNP may be part of the VIP protection pathway through the femtomolar‐acting NAP and through putative interaction with other macromolecules.
Dependence of Anticancer Activity of Camptothecins on Maintaining Their Lactone Function
Authors: GIOVANELLA B. C. , HARRIS N. , MENDOZA J. , CAO Z. , LIEHR J. , STEHLIN J. S.
Published: July 2010

Abstract: Camptothecins contain a lactone ring that exists in the closed form below ph 7. Above 7, the open (CPT+) and the closed (CPT) form coexist in a 50–50 ratio in mouse plasma and in a 90–10 ratio in human plasma due to the high affinity of human serum albumin (HSA) for CPT+. CPT+ is much less toxic than CPT and it is excreted much faster. In complete RPMI 1640 culture medium, the equilibrium CPT+‐CPT is 50–50. If 4% HSA is added, it moves to 90–10 modeling for the human physiological situation.
Preclinical and Clinical Trials of Topoisomerase Inhibitors
Authors: SAIJO NAGAHIRO
Published: July 2010

Abstract: CPT‐11, developed by Yakult Honsha, has achieved the position of standard chemotherapy for colorectal cancer in the United States and in Western countries because CPT‐11+5FU+LV showed survival benefit compared with 5FU‐LV in two randomized controlled trials. CPT‐11 has been distributed to almost all countries. In Japan, combination therapy of CDDP+CPT‐11 was significantly superior to CDDP‐VP‐16 in the treatment of extensive disease small cell lung cancer. This combination is also active against non‐small cell lung cancer. Daiich Pharmaceutical Co. developed a more active nonmasked form of camptothecin derivative, DX‐8915f. The phase I study of a new camptothecin inhibitor, DX‐8915f, has just been completed. The new topoisomerase I inhibitors of indolocarbazol derivatives, NB‐506 and J107088, developed by Banyu Co., have strong antitumor activity and a wide therapeutic ratio. The phase I trial of J107088 is currently ongoing in the United States and Japan. These do not show any cross‐resistance to MDR drugs.
9‐Nitrocamptothecin Liposome Aerosol Treatment of Human Cancer Subcutaneous Xenografts and Pulmonary Cancer Metastases in Mice
Authors: KNIGHT VERNON , KLEINERMAN EUGENIE S. , WALDREP J. CLIFFORD , GIOVANELLA BEPPINO C. , GILBERT BRIAN E. , KOSHKINA NADEZHDA V.
Published: July 2010

Abstract: The purpose of this study was to test the anticancer properties of the water‐insoluble derivative of camptothecin, 9‐nitrocamptothecin (9NC), administered in a liposome formulation (L‐9NC) in aerosol to mice with subcutaneous xenografts of three human cancers and in mice with murine melanoma and human osteosarcoma pulmonary metastases. The drug was formulated with dilauroylphosphatidylcholine and nebulized in particle sizes of 1.2–1.6 μm mass median aerodynamic diameter and a geometric standard deviation of 2.0. The aerosol was generated with the nebulizer flowing at 10 l/min and delivered to mice in sealed plastic cages or in a nose‐only exposure chamber. Aerosol was administered for 15 min to 2 hr daily, delivering deposited doses in the respiratory tract of 8.1–306.7 mg of 9NC/kg. With subcutaneous tumors, growth was greatly inhibited or tumors were undetectable after several weeks of treatment. We also showed that oral dosage with L‐9NC had no detectable effect on cancer growth, and thus the benefit from aerosol treatment was due to pulmonary deposition and not the larger fraction of drug deposited in the nose of mice during aerosol treatment which is promptly swallowed. Intramuscular L‐9NC in slightly larger doses than given in the aerosol had detectable anticancer activity, but it was significantly less than in mice receiving the drug by aerosol. With metastatic pulmonary cancers, treated animals showed highly significantly less cancer growth than control animals. L‐9NC aerosol showed a major therapeutic benefit in the treatment of subcutaneous human cancer xenografts in nude mice, suggesting that cancers at systemic sites might be responsive to this treatment. In addition, the strong anticancer effect of L‐9NC aerosol on pulmonary metastases offers a therapeutic approach for treatment of pulmonary cancers. Thus, L‐9NC aerosol may have applicability in the treatment of cancers throughout the body.
Pharmacokinetics of Orally Administered Camptothecins
Authors: GUPTA ELORA , VYAS VIRAL , AHMED FARHEENA , SINKO PATRICK , COOK THOMAS , RUBIN ERIC
Published: July 2010

Abstract: Phase I trials of oral camptothecins, including camptothecin (CPT) and irinotecan (CPT‐11), have reported substantial interpatient variability in systemic exposure, which could result in suboptimal antitumor activity in some patients or enhanced risk for toxicity in others. This investigation evaluates the contribution of intestinal absorption and first‐pass metabolism in the disposition of oral CPT and CPT‐11, respectively. The transport of CPT in Caco‐2 cell lines (validated model of intestinal drug transport) was concentration dependent and saturable (Vmax: 34×10−5 cm/sec and Km: 20 μM), and was temperature dependent with an activation energy (Ea) of 11.7 kcal/mole. Cumulatively, this data was indicative of carrier‐mediated intestinal transport. In addition, a reduction of transport in the presence of sodium azide plus deoxyglucose suggested ATP dependence. Thus, variable expression and availability of intestinal transporters could contribute to the observed wide variability in the exposure to oral CPT. CPT‐11 is hydrolyzed by the ubiquitous enzyme carboxyl esterase to active SN‐38, and first‐pass metabolism of oral CPT‐11 would include both intestinal and hepatic hydrolysis. Incubation of CPT‐11 with S9 fractions of human liver and intestinal tissues resulted in variable rates of formation of SN‐38. The mean (±SD) specific activities (pmoles/min/mg) were: liver (8.57 ± 10.4, n=8), duodenum (5.06 ± 3.7, n=4), jejunum (6.44 ± 2.8, n=5), ileum (4.81 ± 2.4, n=5), colon (1.93 ± 1.5, n=6), and rectum (0.82, n=1). Interestingly, there was a decrease in SN‐38 formation by tumor tissue compared to matched normal liver and colon tissues. Therefore variable first‐pass metabolism could contribute to the substantial differences in the systemic exposures to CPT‐11 and SN‐38 in patients receiving oral CPT‐11.
In Vitro Antitumor Activity of 9‐Nitro‐Camptothecin as a Single Agent and in Combination with other Antitumor Drugs
Authors: BERNACKI RALPH J. , PERA PAULA , GAMBACORTA PETER , BRUN YSEULT , GRECO WILLIAM R.
Published: July 2010

Abstract: Preclinical studies at Roswell Park Cancer Institute by Minderman, Cao, and Rustum (unpublished results) showed that a combination of SN‐38 and 5‐FU against HCT‐8 human colon carcinoma cells in vitro was synergistic, with the best interaction occurring when the drugs were added sequentially, SN‐38 first. Their in vivo studies using HCT‐8 tumor xenografts implanted s.c. in nude athymic mice demonstrated superior efficacy for a sequential i.v. administration of CPT‐11, 24 hr before 5‐FU. On the basis of these studies, our group has begun to evaluate effects of RFS2000 (9‐nitro‐20(S)‐camptothecin) (9‐NC) in combination with a series of other antitumor agents. Using a panel of human tumor cell lines including A121 ovarian cancer, HCT‐8 colon cancer, H‐460 NSCLC, HT‐1080 fibrosarcoma, and MCF7 mammary cancer, we found that a 2‐hr exposure to 9‐NC resulted in ID50 values of <1.0 μM, whereas continuous exposure to drug resulted in ID50 values of <1.0 nM. Tumor growth inhibitory activities of 5‐FU, gemcitabine, and paclitaxel were determined for comparison. Combinations of these agents were evaluated with 9‐NC using the human HCT‐8 colon tumor cell line. Concurrent and sequential combinations of 9‐NC with 5‐FU had some regions of the concentration‐effect surface with local synergy and some with local antagonism. However, sequential combination of 9NC or SN‐38 followed by 5‐FU, 24 hr later appeared to be highly synergistic at high dose‐effect levels (i.e., ID90), suggesting that sequential drug administration may be more efficacious at high effect level and that the order of drug addition is very important. Overall, our results were similar to that found earlier by Rustum's group with CPT11 (or SN‐38) and 5‐FU, suggesting that sequential combination of 9‐NC (or other camptothecin analogues) followed by 5‐FU has potential for the treatment of cancer in man.
Structure and Seasonality of Nearctic Culex pipiens Populations
Authors: SPIELMAN ANDREW
Published: July 2010

Abstract: The abundance and structure of urban autogenous and anautogenous populations of Culex pipiens mosquitoes were documented systematically in Boston, MA, during three successive years. Autogenous larvae become abundant mainly in enclosed sites and anautogenous larvae in sites that provide free access and egress. Both populations begin to proliferate when the water temperature exceeds 15°C during June. Larval anautogenous mosquitoes increase in abundance 10‐fold in two weeks and autogenous in three weeks. Although anautogenous larvae rapidly disappear after mid‐August when winter diapause commences, the abundance of autogenous larvae continues to increase until mid‐October. The forms generally are reproductively isolated in nature but occasionally hybridize during August and thereafter. Anautogenous females feed mainly on birds; autogenous females generally never feed on blood; and hybrid females appear to feed indiscriminately on avian or mammalian hosts. Such northern C. p. pipiens mosquitoes range as far south as 33°N. Taken together, these observations suggest that C. p. pipiens‐borne pathogens may proliferate in the northern United States until mid‐August and affect human hosts thereafter. Intensity of transmission decreases toward the south.