bluuebunny/crossref_metadata_2025 huggingface dataset:
Recovery of heavy metals from aqueous solution by using radiation crosslinked poly(vinyl alcohol)
Authors: Hegazy El‐Sayed A. , El‐Salmawy K. M. , El‐Naggar A. A.
Published: September 2004

Crosslinked poly(vinyl alcohol) (PVA) and PVA/acrylic acid hydrogels, prepared by γ‐irradiation, were used in the removal of heavy metals from aqueous solution. Comparative studies of the properties of the two hydrogels were made. The application of the prepared hydrogels as adsorbent materials for Cu2+, Co2+, and Ni2+ from aqueous solution was studied. The chemical and physical properties of the hydrogels, before and after adsorption of the heavy metal ions, were investigated by means of thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. The efficiency of such hydrogels for the recovery of metal ions was determined by atomic absorption and UV spectroscopic analysis. The effect of changing pH on the metal uptake was also studied. It was found that the prepared hydrogels have a substantial ability to adsorb metal ions from their solution. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1649–1656, 2004
Confusing dinosaurs with mammals: Tetrapod phylogenetics and anatomical terminology in the world of homology
Authors: Harris Jerald D.
Published: September 2004

At present, three different systems of anatomical nomenclature are available to researchers describing new tetrapod taxa: a nonstandardized traditional system erected in part by Sir Richard Owen and subsequently elaborated by Alfred Romer; a standardized system created for avians, the Nomina Anatomica Avium (NAA); and a standardized system for extant (crown‐group) mammals, the Nomina Anatomica Veterinaria (NAV). Conserved homologous structures widely distributed within the Tetrapoda are often granted different names in each system. The recent shift toward a phylogenetic system based on homology requires a concomitant shift toward a single nomenclatural system also based on both evolutionary and functional morphological homology. Standardized terms employed in the NAA and NAV should be perpetuated as far as possible basally in their respective phylogenies. Thus, NAA terms apply to nonavian archosaurs (or even all diapsids) and NAV terms apply to noncrown‐group mammals and more basal synapsids. Taxa equally distant from both avians and crown‐group mammals may maintain the traditional nonstandardized terminology until a universal anatomical nomenclature for all tetrapods is constructed. © 2004 Wiley‐Liss, Inc.
The bibliometric properties of article readership information
Authors: Kurtz Michael J. , Eichhorn Guenther , Accomazzi Alberto , Grant Carolyn , Demleitner Markus , Murray Stephen S. , Martimbeau Nathalie , Elwell Barbara
Published: September 2004

Digital libraries such as the NASA Astrophysics Data System (Kurtz et al., 2005) permit the easy accumulation of a new type of bibliometric measure, the number of electronic accesses (“reads”) of individual articles. We explore various aspects of this new measure. We examine the obsolescence function as measured by actual reads and show that it can be well fit by the sum of four exponentials with very different time constants. We compare the obsolescence function as measured by readership with the obsolescence function as measured by citations. We find that the citation function is proportional to the sum of two of the components of the readership function. This proves that the normative theory of citation is true in the mean. We further examine in detail the similarities and differences among the citation rate, the readership rate, and the total citations for individual articles, and discuss some of the causes. Using the number of reads as a bibliometric measure for individuals, we introduce the read–cite diagram to provide a two‐dimensional view of an individual's scientific productivity. We develop a simple model to account for an individual's reads and cites and use it to show that the position of a person in the read–cite diagram is a function of age, innate productivity, and work history. We show the age biases of both reads and cites and develop two new bibliometric measures which have substantially less age bias than citations: SumProd, a weighted sum of total citations and the readership rate, intended to show the total productivity of an individual; and Read10, the readership rate for articles published in the last 10 years, intended to show an individual's current productivity. We also discuss the effect of normalization (dividing by the number of authors on a paper) on these statistics. We apply SumProd and Read10 using new, nonparametric techniques to compare the quality of different astronomical research organizations.
Development characterization and use of a high‐performance enzymatic time‐temperature integrator for the control of sterilization process' impacts
Authors: Guiavarc'h Yann , Van Loey Ann , Zuber François , Hendrickx Marc
Published: September 2004

A small sized single‐component enzymatic time temperature integrator (TTI) was developed. It consisted of glass beads coated with Bacillus licheniformis α‐amylase (BLA) and stabilizing additives in a dehydrated form. Post heating residual enzymatic activity was used as a response property of the TTI. Under isothermal conditions, different batches of the system were characterized by zTTI‐values around 13.5°C in the temperature range 100‐130°C as well as by their ability to provide a response within 5 min after thermal processing. When used under non‐isothermal conditions in a model food (silicone spheres), the system allowed to measure process‐values zTTIF121.1°C up to 60 min with an average error of 10.9%. The capabilities of the system were validated in a real solid/liquid food matrix sterilized by retorting. The combination of FTTI‐values with heat transfer simulations based on finite difference calculations allowed for the determination of process values, which evaluated actual process‐values 10°CF121.1°C up to 90 min with an average error of 11.4%. The good performances of the system as well as its easiness of preparation and use, make the latter a valuable biological device for thermal process assessment. © 2004 Wiley Periodicals, Inc.
Membrane chromatography of DNA: Conformation‐induced capacity and selectivity
Authors: Haber Charbel , Skupsky Jonathan , Lee Ann , Lander Russ
Published: September 2004

The chromatographic purification of biological macromolecules requires a novel approach to overcome some of the pore size limitations of commercially available resins. Membrane adsorbers offer the potential for better resolution as well as productivity. Sharp peaks are gained by the rapid exchange rate with the adsorbing membranes associated with the convective flow path, in contrast to the pore diffusion requirement for resin exchange. The resolution advantage is preserved even when the very short bed heights of membranes are exploited for the purpose of exceptionally high flow rates and productivity.

Breakthrough experiments were used to assess the membrane dynamic loading capacities of flexible macromolecules using supercoiled (SC) DNA as a model system. In contrast to reports for smaller biomolecules such as proteins and antibodies, the dynamic capacity for DNA was found to be highly dependent on flow rates and concentrations. Increasing flow rates induced DNA elongation, which increased the surface coverage and, in turn, lowered the capacity. Increasing concentrations beyond C*, the overlap concentration, led to exclusion‐volume interactions, which reduced the size of DNA and increased the membrane adsorber capacity. In the chromatographic mode, membranes with a strongly positive charge were able to resolve various isoforms of DNA, surpassing the capabilities of analogous chromatographic resins. In this study, we found that the convective‐flow‐induced‐structural behavior of DNA is responsible for the resolution in separation. © 2004 Wiley Periodicals, Inc.
Fractionation of protein, RNA, and plasmid DNA in centrifugal precipitation chromatography using cationic surfactant CTAB containing inorganic salts NaCl and NH4Cl
Authors: Tomanee Panarat , Hsu James T. , Ito Yoichiro
Published: September 2004

Centrifugal precipitation chromatography (CPC) is a separation system that mainly employs a moving concentration gradient of precipitating agent along a channel and solutes of interest undergo repetitive precipitation‐dissolution, fractionate at different locations, and elute out from the channel according to their solubility in the precipitating agent solution. We report here for the first time the use of a CPC system for fractionation of protein, RNA, and plasmid DNA in clarified lysate produced from bacterial culture. The cationic surfactant cetyltrimethylammonium bromide (CTAB) was initially used as a precipitating agent; however, all biomolecules showed no differential solubility in the moving concentration gradient of this surfactant and, as a result, no separation of protein, RNA, and plasmid DNA occurred. To overcome this problem, inorganic salts such as NaCl and NH4Cl were introduced into solution of CTAB. The protein and RNA were found to have higher solubility with the addition of these salts and separated from the plasmid DNA. Decreasing surface charge density of CTAB upon addition of NaCl and NH4Cl was believed to lead to lower surfactant complexation, and therefore caused differential solubility and fractionation of these biomolecules. Addition of CaCl2 did not improve solubility and separation of RNA from plasmid DNA. © 2004 Wiley Periodicals, Inc.
Self‐assembly DNA‐conjugated polymer for detection of single nucleotide polymorphism
Authors: Taira Shu , Yokoyama Kenji
Published: September 2004

We developed a self‐assembly DNA‐conjugated polymer based on polyacrylic acid (PAA) for DNA chip fabrication. A 20‐mer single‐stranded DNA (ssDNA, probe‐1), and 3‐(2‐pyridyldithio)propionyl hydrazide (PDPH), for promoting self‐assembled immobilization, were both covalently attached to PAA as sidechains. This DNA‐conjugated PAA was then spontaneously immobilized on a gold substrate. Probe‐1 on the immobilized polymer was hybridized to a 34‐mer ssDNA (probe‐2), which had the sequence desired for analyzing the target DNA. The fluorescence intensity after incubating the P‐1 DNA‐conjugated polymer with probe‐2 DNA was much higher than with control sequence in the first hybridization. The interactions between target DNA and the DNA‐conjugated PAA were investigated by fluorescence measurement. The interaction of fully matched target DNA with this immobilized DNA conjugated polymer has been studied at different ion strength conditions. SNP sequences as targets showed less than 15% the intensity of fully matched target DNA in the second hybridization, indicating that the gold surfaces coated with the DNA‐conjugated PAA was highly specific to fully matched DNA. The DNA‐conjugated PAA immobilized on a gold substrate is characterized by reduced nonspecific adsorption, due to less electrostatic repulsion as well as the polymer coating. Therefore, DNA‐conjugated PAA can be used for probe DNA immobilization method. © 2004 Wiley Periodicals, Inc.
Roles and applications of small heat shock proteins in the production of recombinant proteins in Escherichia coli
Authors: Han Mee‐Jung , Park Si Jae , Park Tae Jung , Lee Sang Yup
Published: September 2004

Proteome profiling of the inclusion body (IB) fraction of recombinant proteins produced in Escherichia coli suggested that two small heat shock proteins, IbpA and IbpB, are the major proteins associated with IBs. In this study, we demonstrate that IbpA and IbpB facilitate the production of recombinant proteins in E. coli and play important roles in protecting recombinant proteins from degradation by cytoplasmic proteases. We examined the cytosolic production, and Tat‐ or Sec‐dependent secretion of the enhanced green fluorescent protein (EGFP) in wild type, ibpAB− mutant, and ibpAB‐amplified E. coli strains. Analysis of fluorescence histograms and confocal microscopic imaging revealed that over‐expression of the ibpA and/or ibpB genes enhanced cytosolic EGFP production whereas knocking out the ibpAB genes enhanced secretory production. This strategy seems to be generally applicable as it was successfully employed for the enhanced cytosolic or secretory production of several other recombinant proteins in E. coli. © 2004 Wiley Periodicals, Inc.
Macrolide‐ and tetracycline‐adjustable siRNA‐mediated gene silencing in mammalian cells using polymerase II‐dependent promoter derivatives
Authors: Malphettes Laetitia , Fussenegger Martin
Published: September 2004

RNA interference has emerged as a powerful technology for downregulation of specific genes in cells and animals. We have pioneered macrolide‐ and tetracycline‐adjustable short interfering RNA (siRNA) expression for conditional target gene translation fine‐tuning in mammalian/human cell lines based on modified RNA polymerase II promoters. Established macrolide‐ and tetracycline‐dependent transactivators/trans‐silencers bound and activated modified target promoters tailored for optimal siRNA expression in response to clinical antibiotics' dosing regimes and modulated desired target genes in Chinese hamster ovary (CHO‐K1) and human fibrosarcoma (HT‐1080) cells with high precision. Further optimization of adjustable RNA polymerase II‐based siRNA‐specific promoters as well as their combination with various transmodulators enabled near‐perfect regulation configurations in specific cell types. Devoid of major genetic constraints compared to basic RNA polymerase III‐based siRNA‐specific promoters, we expect RNA polymerase II counterparts to significantly advance siRNA‐based molecular interventions in biopharmaceutical manufacturing and gene‐function analysis as well as gene therapy and tissue engineering. © 2004 Wiley Periodicals, Inc.
Kinetics and modeling of reductive dechlorination at high PCE and TCE concentrations
Authors: Yu Seungho , Semprini Lewis
Published: September 2004

Two biokinetic models employing the Michaelis‐Menten equation for anaerobic reductive dechlorination of tetrachloroethylene (PCE) and trichloroethylene (TCE) were developed. The models were compared with results from batch kinetic tests conducted over a wide range of PCE and TCE concentrations with two different dechlorinating cultures. One model applies Michaelis‐Menten kinetics with competitive inhibition among chlorinated aliphatic hydrocarbons (CAHs), while the other model includes both competitive inhibition and Haldane inhibition at high CAH concentrations. Model simulations with competitive inhibition simulated the experimental results well for PCE concentrations lower than 300 μM. However, simulations deviated from the experimental observations for PCE or TCE concentrations greater than 300–400 μM. The kinetic model that incorporated both competitive and Haldane inhibitions better simulated experimental data for PCE concentrations near the solubility limit (1000 μM), and TCE concentrations at half its solubility limit (4000 μM). Based on the modeling analysis of the experimental results, the PM culture (Point Mugu, CA) had very high Haldane inhibition constants for cis‐1,2‐dichlororethylene (c‐DCE) and vinyl chloride (VC) (6000 and 7000 μM, respectively), indicating very weak Haldane inhibition, while the EV culture (the Evanite site in Corvallis, OR) had lower Haldane inhibition constants for TCE, c‐DCE, and VC of 900, 750, and 750 μM, respectively. The BM culture (a binary mixed culture of the PM and EV cultures) had transformation abilities that represented the mixture of the EV and PM cultures. Model simulations of the BM culture transformation abilities were well represented by separate rate equations and model parameters for the two independent cultures that were simultaneously solved. Modeling results indicated that a combination of competitive and Haldane inhibition kinetics is required to simulate dechlorination over a broad range of concentrations up to the solubility limit of PCE and half the solubility limit of TCE. © 2004 Wiley Periodicals, Inc.
Determination of piceatannol in rat serum and liver microsomes: pharmacokinetics and phase I and II biotransformation
Authors: Roupe Kathryn , Teng Xiao Wei , Fu Xing , Meadows Gary G. , Davies Neal M.
Published: September 2004

A method of analysis of piceatannol in biological ﬂuids is necessary to study the kinetics of in vitro and in vivo metabolism and determine its concentration in foodstuffs. A novel and simple high‐performance liquid chromatographic method was developed for simultaneous determination of piceatannol and products of its metabolism in rat serum and liver microsomes. Serum, or microsomes (0.1 mL), were precipitated with acetonitrile after addition of the internal standard, 4‐methylumbelliferone. Separation was achieved on a phenomenex C18 column (250 × 4.6 mm i.d., 5 µm) equipped with a phenomenex C18 (4 × 3.0 mm i.d., 5 µm) guardcolumn with ﬂuorescence excitation at 320 nm and emission at 420 nm. Separation was also possible with UV detection at 310 nm. The ﬂuorescent calibration curves were linear ranging from 0.05 to 100 µg/mL. The mean extraction efﬁciency was >95%. Precision of the assay was <10% (coefﬁcient of variation), and was within 10% at the limit of quantitation (0.05 ng/mL). Bias of the assay was lower than 7%. The limit of detection was 50 ng/mL for a 0.1 mL sample. The assay was applied successfully to the in vitro kinetic study of metabolism of piceatannol in rat liver microsomes and pharmacokinetics in rats. Three metabolites of piceatannol have been identiﬁed. Copyright © 2004 John Wiley & Sons, Ltd.
Study on polymerization of the pharmaceutical substances isohexenylnaphthazarins
Authors: Assimopoulou A. N. , Papageorgiou V. P.
Published: September 2004

Polymerization of naturally occurring isohexenylnaphthazarins (IHN), such as alkannin, shikonin (A/S) and their derivatives, which are potent pharmaceutical substances, signiﬁcantly affects their use in pharmaceuticals, cosmetics and as food colorants, because it leads to reduction of the lustre of their red coloration, a decrease in their solubility and reduces the active monomeric IHN derivatives. In the present study, the inﬂuence of several crucial variables (processing and storage) was experimentally investigated on IHN polymerization by size exclusion chromatography (SEC). Temperature and solvent polarity increased signiﬁcantly the concentration of hydroxynaphthoquinone (HNQ) polymers, while air and light exposure conditions did not signiﬁcantly affect IHN polymerization. Low temperatures are proposed for all processes of industrial production of pharmaceutical preparations containing IHN and HNQ. An optimization of the industrial conditions used for the preparation of pharmaceutical and cosmetic preparations containing IHN, maximizing the active monomeric IHN fraction, was performed. Copyright © 2003 John Wiley & Sons, Ltd.
Determination of bisphenol A in human breast milk by HPLC with column‐switching and ﬂuorescence detection
Authors: Sun Yen , Irie Miki , Kishikawa Naoya , Wada Mitsuhiro , Kuroda Naotaka , Nakashima Kenichiro
Published: September 2004

A highly sensitive HPLC method was developed for the determination of xenoestrogenic compound, bisphenol A (BPA) in human breast milk samples. After a two‐step liquid–liquid extraction, BPA was derivatized with ﬂuorescent labeling reagent, 4‐(4,5‐diphenyl‐1H‐imidazol‐2‐yl)benzoyl chloride (DIB‐Cl). The excess ﬂuorescent reagent could be removed effectively using a column‐switching system. The separation of DIB‐BPA from endogenous materials in milk was carried out on two C18 columns and ﬂuorescence intensity was monitored at 475 nm with the excitation of 350 nm. A good linearity (r = 0.994) was observed of BPA in the concentration range of 0.2–5.0 ng mL−1 in breast milk, and the detection limit was 0.11 ng mL−1 at a signal‐to‐noise ratio of 3. Intra‐ and inter‐day precision (RSD, %) were less than 8.7 and 10.4, respectively. Twenty‐three breast milk samples of healthy lactating women were analyzed for the BPA concentration; the mean value was 0.61 ± 0.20 ng mL−1, with no correlation to the lipid content of milk samples. Copyright © 2004 John Wiley & Sons, Ltd.
Study on isohexenylnaphthazarins polymerization in alkaline media
Authors: Assimopoulou A. N. , Papageorgiou V. P.
Published: September 2004

The chiral pair alkannin and shikonin (A/S) and their isohexenylnaphthazarin (IHN) esters, which are naturally occurring hydroxynaphthoquinones (HNQ), are potent pharmaceutical substances with a wide spectrum of biological activity. The stability of A/S and their derivatives during process and storage is crucial to their use as drugs, cosmetics and food additives. The inﬂuence of alkaline media and of IHN esters hydrolysis was experimentally investigated on IHN polymerization by size exclusion chromatography (SEC). It was proved that during IHN esters hydrolysis, polymeric A/S and IHN are formed. An optimization of the hydrolysis conditions of IHN esters was also approached in terms of polymerization. Hydrolysis of IHN from a pure mixture of pigments proved preferable to that of preliminary root extracts by means of IHN polymerization, even for analytical determination; non‐polar solvents are proposed for the extraction of IHN from roots, followed by hydrolysis, aiming to minimize the polymeric IHN and A/S formed. It was also proved that polymerization of IHN in alkaline media and during hydrolysis of IHN esters proceeds through the intermediate formation of semiquinones; after acidiﬁcation, coupling of semiquinones with phenoxyl radicals results in polymeric IHN structures. Copyright © 2004 John Wiley & Sons, Ltd.
Cover Picture: Expanded Utility of the Native Chemical Ligation Reaction (Chem. Eur. J. 19/2004)
Authors: Yeo Dawn S. Y. , Srinivasan Rajavel , Chen Grace Y. J. , Yao Shao Q.
Published: September 2004

The cover picture shows the X‐ray structure of Sce VMA intein from Saccharomyces cerevisiae in the background. This intein has been extensively modified to overexpress proteins that have a C‐terminal thioester, which is the key component for the so‐called "Native Chemical Ligation Reaction" shown in the foreground. More details could be found in the article by S. Q. Yao et al. on p. 4664 ff.
Absolute configurational determination of an all‐trans‐retinal dimer isolated from photoreceptor outer segments
Authors: Fishkin Nathan , Pescitelli Gennaro , Sparrow Janet R. , Nakanishi Koji , Berova Nina
Published: September 2004

An all‐trans‐retinal (ATR) dimer (1) isolated from photoreceptor outer segments was found to have a stereogenic center at C13′ flanked by tetraene (295 nm) and hexaenal (438 nm) chromophores. Analytical chiral HPLC (Chiralcel OD) revealed that the isolated retinoid had formed in 13% enantiomeric excess. Using a combination of 1H‐1H NOESY constraints, molecular modeling, and CD exciton coupling analysis, it was determined that the favored enantiomer was 13′(R). Three low‐energy conformers of the 13′(S) model were found with MMFF/DFT and were used to calculate the CD spectrum of the ATR dimer (DeVoe method). The Boltzmann weighted spectrum was found to exhibit a positive exciton couplet, in excellent agreement with the experimental spectrum for the first eluted enantiomer. This further suggested that despite the large energy difference between the two interacting chromophores, the dominant source of optical activity in the CD spectrum is the nondegenerate exciton mechanism. Chirality 16:637–641, 2004. © 2004 Wiley‐Liss, Inc.
Enantiomers of C5‐chiral 1‐acetyl‐3,5‐diphenyl‐4,5‐dihydro‐(1H)‐pyrazole derivatives: Analytical and semipreparative HPLC separation, chiroptical properties, absolute configuration, and inhibitory activity against monoamine oxidase
Authors: Cirilli Roberto , Ferretti Rosella , Gallinella Bruno , Turchetto Luciana , Bolasco Adriana , Secci Daniela , Chimenti Paola , Pierini Marco , Fares Vincenzo , Befani Olivia , La Torre Francesco
Published: September 2004

The HPLC enantiomer separation of a novel series of C5‐chiral 1‐acetyl‐3‐(4‐hydroxy‐ and 2,4‐dihydroxyphenyl)‐5‐phenyl‐4,5‐dihydro‐(1H)‐pyrazole derivatives, with inhibitory activity against monoamine oxidases (MAO) type A and B, was accomplished using polysaccharide‐based chiral stationary phases (CSPs: Chiralpak AD, Chiralcel OD, and Chiralcel OJ). Pure alcohols, such as ethanol and 2‐propanol, and typical normal‐phase binary mixtures, such as n‐hexane and alcohol modifier, were used as mobile phases. Single enantiomers of several analytes examinated were isolated on a semipreparative scale, and their chiroptical properties were measured. The assignment of the absolute configuration was established for one compound by single‐crystal X‐ray diffraction method and for the other three by CD spectroscopy. The inhibitory activity against MAO of racemic samples and single enantiomers were evaluated in vitro. Chirality 16:625–636, 2004. © 2004 Wiley‐Liss, Inc.
Morbidity and mortality of colorectal carcinoma surgery differs by insurance status
Authors: Kelz Rachel Rapaport , Gimotty Phyllis A. , Polsky Daniel , Norman Sandra , Fraker Douglas , DeMichele Angela
Published: September 2004

BACKGROUND

Uninsured and underinsured patients are reported to be at an increased risk for impaired access to healthcare, delayed medical treatment, and the receipt of substandard care. These differences in care may result in disparities in surgical outcomes among patients with different types of insurance. In the current study, the authors examined associations between the insurance provider and short‐term surgical outcomes after surgery for colorectal carcinoma and evaluated the extent to which two risk factors (comorbid disease and admission type) might explain any observed association.

METHODS

The authors conducted a nationally representative retrospective cohort study of 13,415 adults ages 40–64 years who were admitted for surgery for colorectal carcinoma to hospitals that participated in the Agency for Healthcare Research and Quality Healthcare Cost and Utilization Project National Inpatient Sample, releases 6 and 7, in 1997 and 1998. Multivariate logistic regression models were developed to describe the correlations between insurance status and the risks of a postoperative complication or postoperative death after adjustment for socioeconomic factors, comorbid conditions, and admission type.

RESULTS

Uninsured and Medicaid patients were found to have more emergent admissions and more comorbid disease compared with patients with private health insurance. Patients without private health insurance had higher rates of postoperative complications and in‐hospital death compared with those patients with private insurance. After adjusting for patient and hospital characteristics, patients with Medicaid were found to be 22% more likely to develop a complication during their hospital admission (odds ratio [OR] of 1.22; 95% confidence interval [95%CI], 1.06–1.40) and 57% more likely to die postoperatively (OR of 1.57; 95% CI, 1.01–2.42) compared with patients with private insurance.

CONCLUSIONS

The current study findings suggest that the uninsured and Medicaid populations are at greater risk of developing postoperative complications and dying than the privately insured population due only in part to preexisting medical comorbidities and emergent admission type. Cancer 2004. © 2004 American Cancer Society.
Autoregulation of the N‐myc gene is operative in neuroblastoma and involves histone deacetylase 2
Authors: Kim Marianne K. H. , Carroll William L.
Published: September 2004

BACKGROUND

Autoregulation of the myc gene family is a negative feedback mechanism known to occur at high levels of Myc expression. Loss of this mechanism and associated Myc overexpression has been observed in human tumors, thereby contributing to tumorigenesis. The childhood tumor neuroblastoma is characterized by N‐myc amplification in aggressive and highly proliferative tumors that occur in a subset of patients. The precise molecular mechanism of autoregulation is unknown, and previous observations indicated that N‐myc autoregulation was intact only in single‐copy neuroblastoma cell lines.

METHODS

Transient reporter assays and trichostatin A (TSA) experiments were performed to evaluate several candidate genes, including Mxi1, c‐myc promoter binding protein 1 (MBP‐1), Miz, and histone deacetylase 2 (HDAC2), for their involvement in N‐myc autoregulation. Mxi1 and HDAC2 were examined further for their expression levels and effects on endogenous N‐myc levels. Finally, their recruitments to the N‐myc promoter were investigated by chromatin immunoprecipitation (ChIP).

RESULTS

The autoregulatory circuit was operative, even in amplified cell lines. Mxi1 consistently showed a modest effect in down‐regulating N‐myc in transient reporter assays. Overexpression of the c‐myc, Mxi1, and mHDAC2 genes resulted in a threefold to fourfold decrease in endogenous N‐myc levels. Mxi1 and HDAC2 were up‐regulated by N‐Myc in an myc‐inducible cell line and in N‐myc‐expressing cell lines. In addition, down‐regulation of the N‐myc promoter was relieved in the presence of TSA. Increased association of HDAC2 with the autoregulatory region within the N‐myc promoter by ChIP was observed upon down‐regulation of endogenous N‐myc.

CONCLUSIONS

The autoregulatory circuit was intact in both amplified and single‐copy neuroblastoma cell lines. Furthermore, myc gene autoregulation occurred through histone deacetylation. Cancer 2004. © 2004 American Cancer Society.
Class I and class II ganglion cells of rabbit retina: A structural basis for X and Y (brisk) cells
Authors: Famiglietti Edward V.
Published: September 2004

Morphological studies of rabbit retina have identified ganglion cells resembling “alpha” cells but none resembling cat “beta” cells. Four distinct types of class I cell, similar to alpha cells, were identified, each narrowly stratified and differing from the other three principally in the level of dendritic branching. These four levels of dendritic branching flank the two starburst/cholinergic amacrine cell substrata that mark the middle of sublaminae a and b. Compared with the other three, class Ia2 cells are the largest in cell body and dendritic field size, are sometimes homotypically dye coupled, and have slightly broader dendritic stratification. Class Ia2 and the slightly smaller class Ib2 cells form a paramorphic pair. Compared with class I cells, class II cells have smaller dendritic fields; a greater tendency to “tufted” dendritic branching, as shown in the companion paper; branching at one of three levels of the IPL; and similarly narrow stratification. Class IIa and class Ia1 cells branch at the same level, as do class IIb1 and class Ib1 cells. Class IIb2 cells branch slightly nearer the ganglion cell layer than class Ib2 cells and costratify with “blue‐ON” cone bipolar cells. The class IIa and IIb2 cells form a paramorphic pair, whereas class IIb1 cells appear to be unpaired. The four types of class I cell probably correspond to ON‐ and OFF‐center brisk‐transient, fast‐movement and slow‐movement cells, whereas the three types of class II cell probably correspond to ON‐ and OFF‐center brisk‐sustained and color‐coded ON‐center X cells. J. Comp. Neurol. 478:323–346, 2004. © 2004 Wiley‐Liss, Inc.
Distribution of transcription factor inducible cyclicAMP early repressor (ICER) in rodent brain and pituitary
Authors: Kell Christian A. , Dehghani Faramarz , Wicht Helmut , Molina Carlos A. , Korf Horst‐Werner , Stehle Jörg H.
Published: September 2004

In morphogenetic dynamics of neurons, and in adaptive physiology of brain function, transcription factors of the cyclicAMP signaling pathway, such as activator cyclicAMP responsive element binding protein (CREB) and inhibitor inducible cyclicAMP early repressor (ICER), play an important role. In particular, the presence of the transcription factor ICER in neurons or neuroendocrine cells suggests the need for the gating of an up‐regulated gene expression. Little is known, however, about the natural distribution of the inhibitory transcription factor ICER. We, therefore, mapped the rodent brain and pituitary for an ICER immunoreaction and found a nuclear staining for this transcription factor. ICER‐positive glial cells were found throughout the brain. ICER‐positive neurons were found in sensory input centers, like the olfactory bulb, or sensory brain stem nuclei, and in hypothalamic nuclei involved in central neuroendocrine control. In addition, neuroendocrine/endocrine transducers, like the pituitary and the pineal gland showed a high basal presence of ICER. Our data show that a basic ICER level is required by many cell systems and can be seen as an anticipatory and/or a protective measure in systems with superior reactive dynamics. J. Comp. Neurol. 478:379–394, 2004. © 2004 Wiley‐Liss, Inc.
Synaptic and extrasynaptic localization of brain‐derived neurotrophic factor and the tyrosine kinase B receptor in cultured hippocampal neurons
Authors: Swanwick Catherine Croft , Harrison Madaline B. , Kapur Jaideep
Published: September 2004

Brain‐derived neurotrophic factor (BDNF) regulates synapses, but the distribution of BDNF and its receptor TrkB relative to the location of glutamatergic and γ‐aminobutyric acidergic (GABAergic) synapses is presently unknown. Immunocytochemistry was performed in primary hippocampal neuron cultures to determine whether BDNF and TrkB are preferentially localized to excitatory or inhibitory markers at 7, 14, and 21 days in vitro (DIV). Glutamatergic sites were localized with vesicular glutamate transporter type 1 (VGLUT1) as presynaptic marker and the NR1 subunit of the NMDA receptor and the GluR1 subunit of the AMPA receptor as receptor markers. GABAergic sites were labeled with the 65‐kDa isoform of glutamic acid decarboxylase (GAD‐65) as presynaptic marker and the γ2 subunit of the GABAA receptor as receptor marker. During development, <30% of BDNF punctae and TrkB clusters were localized to glutamatergic and GABAergic markers. Because their rates of colocalization did not change from 7 to 21 DIV, this study details the distribution of BDNF and TrkB at 14 DIV. BDNF was preferentially colocalized with glutamatergic markers VGLUT1 and NR1 (∼30% each). TrkB was also relatively highly colocalized with VGLUT1 and NR1 (∼20% each) but was additionally highly colocalized with GABAergic markers GAD‐65 (∼20%) and γ2 (∼30%). NR1 clusters colocalized with BDNF puncta and TrkB clusters were mostly extrasynaptic, as were γ2 clusters colocalized with TrkB clusters. These results show that, whereas most BDNF and TrkB protein is extrasynaptic, BDNF is preferentially associated with excitatory markers and that TrkB is associated equally with excitatory and inhibitory markers. J. Comp. Neurol. 478:405–417, 2004. © 2004 Wiley‐Liss, Inc.
Variable effects of chronic subcutaneous administration of rotenone on striatal histology
Authors: Zhu Chunni , Vourc'h Patrick , Fernagut Pierre‐Olivier , Fleming Sheila M. , Lacan Sanja , Dicarlo Cheryl D. , Seaman Ronald L. , Chesselet Marie‐Françoise
Published: September 2004

When infused in rats, rotenone, a mitochondrial complex I inhibitor, induces alterations that resemble the histological changes of Parkinson's disease, particularly degeneration of the nigrostriatal dopaminergic system. However, the specificity of rotenone effects has been challenged recently. We have re‐examined the alterations caused by rotenone in the substantia nigra and the striatum of rats after infusion of rotenone (2 mg/kg per day s.c.) for 21 days. Three patterns of striatal tyrosine‐hydroxylase immunoreactivity (TH‐IR) were observed: 46% of animals showed no reduction, and 46% of animals showed diffuse reduction in TH‐IR, whereas one animal presented a focal loss of TH‐IR in the striatum. Confocal microscopy analysis showed that the vesicular monoamine transporter (VMAT2) was decreased in parallel with TH‐IR, strongly suggesting a loss of striatal DA nerve terminals in animals with diffuse or central TH‐IR loss. However, no significant loss of TH‐IR neurons was observed in the substantia nigra. Analysis of NeuN and DARPP‐32 immunoreactivity, and Nissl staining, in the striatum showed no striatal neuronal loss in animals with either preserved TH‐IR or diffuse TH‐IR reduction. However, in the animal with focal TH‐IR loss, severe neuronal loss was evident in the center and the periphery of the striatum, together with microglial activation detected by OX‐6 and OX‐42 staining. Thus, in most cases, chronic subcutaneous infusion of low doses of rotenone does not induce significant striatal neuronal loss, despite TH‐IR and VMAT‐IR reduction in a subset of animals, supporting the use of rotenone as a model of Parkinson's disease under carefully controlled experimental conditions. J. Comp. Neurol. 478:418–426, 2004. © 2004 Wiley‐Liss, Inc.
A new model for network traffic forecast based on user's mobility in cellular networks with highway stretches
Authors: Bolla Raffaele , Repetto Matteo
Published: September 2004

Wireless communications have always faced the scarceness of bandwidth and until today the cellular division has solved this problem by making radio cells always smaller. However, as cell size is reduced, more users will probably require handoffs, and signaling can overload the system. Further, the decrease in cell dimension cannot ensure the best utilization of system resources, because user density in the cell is not constant over the time. Dynamic allocation might be the solution, but it is a complex task, basically due to complexity of the models for the mobility prediction, especially in those environments where users move very fast (e.g. highways). This last one is a typical environment where high mobility of vehicles does not allow small cell sizes and thus system capacity is intrinsically bounded.

In this paper, we deploy an analytical model for a cellular network operating in a high mobility environment. Such a model is capable of representing and forecasting wireless system evolution in terms of channel occupancy, starting from the current state of the mobile network and road traffic. This model has been defined by integrating a vehicular traffic model with a wireless cellular communication one. With such approach the dynamic behaviour of the most critical mobile terminals, those associated with vehicles, are described in a very precise and specific way with respect to mobility.

Many results obtained with specific simulation tools and herein reported show the good behaviour of our proposal. Copyright © 2004 John Wiley & Sons, Ltd.
GPSPA: a new adaptive algorithm for maintaining shortest path routing trees in stochastic networks
Authors: Misra Sudip , Oommen B. John
Published: September 2004

This paper presents a new efficient solution to the Dynamic Shortest Path Routing Problem, using the principles of Generalized Pursuit Learning. It proposes an efficient algorithm for maintaining shortest path routing trees in networks that undergo stochastic updates in their structure. It involves finding the shortest path in a stochastic network, where there are continuous probabilistically based updates in link‐costs. In vast, rapidly changing telecommunications (wired or wireless) networks, where links go up and down continuously and rapidly, and where there are simultaneous random updates in link costs, the existing algorithms are inefficient. In such cases, shortest paths need to be computed within a very short time (often in the order of microseconds) by scanning and processing the minimal number of nodes and links. The proposed algorithm, referred to as the Generalized Pursuit Shortest Path Algorithm (GPSPA), will be very useful in this regard, because after convergence, it seems to be the best algorithm to‐date for this purpose. Indeed, it has the advantage that it can be used to find the shortest path within the ‘statistical’ average network, which converges irrespective of whether there are new changes in link‐costs or not. Existing algorithms are not characterized by such a behaviour inasmuch as they would recalculate the affected shortest paths after each link‐cost update. The algorithm has been rigorously evaluated experimentally, and it has been found to be a few orders of magnitude superior to the algorithms available in the literature. Copyright © 2004 John Wiley & Sons, Ltd.
Pharmacodynamic differences between species exemplified by the novel anticancer agent CHS 828
Authors: Lindhagen Elin , Vig Hjarnaa Pernille‐Julia , Friberg Lena E. , Latini Scilla , Larsson Rolf
Published: September 2004

When a candidate drug enters clinical trials, decisions regarding dosing are mainly based on animal data. Occasionally, toxicity problems are faced in the clinic because of unexpected species differences in pharmacokinetics or pharmacodynamics between humans and preclinical species. Fludarabine and topotecan are examples of such drugs. In the first clinical trials of the new agent CHS 828, the maximum tolerated dose was reached earlier than expected from animal data. This paper discusses the issue of species differences in the development of anticancer drugs, and preclinical models for detection and quantification of such differences. Pharmacokinetic and hematological toxicity data of CHS 828 from studies in rats and humans are presented. In vitro sensitivity to CHS 828 and some established cytotoxic agents was measured in lymphocytes from humans and rats and in a panel of human and rodent cell‐lines. 10–100 times higher CHS 828 exposure was tolerated by rats than by patients. In both in vitro cell systems, CHS 828 showed higher potency in human cells compared to rodent cells. A species difference was evident also for fludarabine, but not for doxorubicin and cisplatin. CHS 828 pharmacokinetics were similar across species. In conclusion, the lower tolerance of CHS 828 in humans than in rats could be detected in vitro in cultures of peripheral lymphocytes. Preclinical studies of species differences could help the interpretation of in vivo effect studies as well as the choice of starting dose for clinical trials. We suggest peripheral lymphocytes from different species as a potential model system for such studies. Drug Dev. Res. 61:218–226, 2004. © 2004 Wiley‐Liss, Inc.
Northern ring conformation of methanocarba‐adenosine 5′‐triphosphate required for activation of P2X receptors
Authors: Dunn Philip M. , Kim Hak Sung , Jacobson Kenneth A. , Burnstock Geoffrey
Published: September 2004

Replacement of the ribose moiety of adenosine 5′‐triphosphate (ATP) with a carbocyclic ring constrained in either the Northern (N) or Southern (S) conformation produces agonists with widely differing activities at P2Y receptors (Kim et al. [2002] J Med Chem 45:208–218). We have used whole cell patch clamp recording to investigate the agonist activity of these two methanocarba analogs of ATP at four different P2X receptors (P2X1, P2X2, P2X3, and P2X2/3). On dorsal root ganglion neurons, (N) methanocarba‐ATP ((1′S,2′R,3′S,4′R,5′S)‐4‐(6‐amino‐9H‐purin‐9‐yl)‐1‐[triphosphoryloxymethyl] bicyclo[3.1.0]hexane‐2,3‐diol; MRS 2340) activated rapidly‐desensitizing (P2X3) and slowly‐desensitizing (P2X2/3) receptors with a similar potency to ATP. In contrast, (S) methanocarba‐ATP ((±)‐5‐(6‐amino‐9H‐purin‐9‐yl)‐1‐[triphosphoryloxymethyl] bicycle [3.1.0]hexane‐2,3‐diol MRS 2312) was devoid of agonist activity. On nodose ganglion neurones, that express mainly P2X2/3 receptors, ATP evoked a slowly desensitizing inward current with an EC50 value of 26 µM. MRS 2340 was an effective agonist, but less potent than ATP, while MRS 2312 at concentrations up to 100 µM produced a barely detectable response. On mammalian cell lines expressing recombinant hP2X1 and hP2X2 receptors, MRS 2340 evoked inward currents similar in amplitude to those produced by the same concentration of ATP or α,β‐mATP. In contrast, MRS 2312 failed to give a detectable response. Although the conformation of the ribose affects agonist activity at P2Y receptors, there is a strong requirement for the (N) conformation for the activation of these P2X receptors. Furthermore, the region of the agonist binding site that accommodates the ribose moiety appears to be highly conserved among different P2X receptors. Drug Dev Res 61:227–232, 2004. © 2004 Wiley‐Liss, Inc.
Characterization of mouse MAGE‐derived H‐2Kb‐restricted CTL epitopes
Authors: Eggert Andreas O. , Andersen Mads H. , Voigt Heike , Schrama David , Kämpgen Eckhardt , Straten Per thor , Becker Jürgen C.
Published: September 2004

Immunogenic peptide epitopes from tumor‐associated antigens serve as targets for cellular immune responses in numerous clinical trials for therapeutic vaccinations. From these it became evident that prevailing questions can only be addressed in animal models. Hence, problems arise from the fact that while for human melanoma many different immunogenic peptide epitopes are known, for mouse melanoma the available selection is very restricted. To overcome this limitation, we applied reverse immunology to identify Kb‐restricted epitopes derived of mouse MAGE. Two epitopes which bind strongly to Kb were selected to test for their immunogenicity in vivo. Spleen cells from mice vaccinated by intradermal injection of mature dendritic cells pulsed with these peptides displayed reactivity to the respective epitopes as measured by enzyme‐linked immunospot assays and tetramer staining. The processing and presentation of these epitopes was evident by the killing of melanoma cells by the vaccination‐induced T cells. Moreover, intravenous challenge with syngeneic melanoma cells demonstrated the protective immunity induced by this vaccination. In summary, we demonstrate the immunogenicity of two Kb‐restricted peptide epitopes derived from mouse MAGE proteins which may serve as valuable tool for preclinical evaluation of vaccination strategies.
Expression of selectin ligands on murine effector and IL‐10‐producing CD4+ T cells from non‐infected and infected tissues
Authors: Kretschmer Ute , Bonhagen Kerstin , Debes Gudrun F. , Mittrücker Hans‐Willi , Erb Klaus J. , Liesenfeld Oliver , Zaiss Dietmar , Kamradt Thomas , Syrbe Uta , Hamann Alf
Published: September 2004

Endothelial selectins are crucial for the recruitment of leukocytes into sites of inflammation. On T cells, ligands for selectins become induced upon differentiation into the effector/memory stage. Initial in vitro studies suggested a correlation between the Th1 phenotype and ligand expression, but whether this also holds true in vivo remained uncertain. We here analyzed selectin ligands on CD4+ T cells producing IFN‐γ, IL‐4 or IL‐10, prototypic cytokines of the Th1, Th2 and Tr1 subset, respectively. We analyzed mice infected with influenza virus, the bacterium Listeria, and the parasites Toxoplasma (all Th1 models) or Nippostrongylus (Th2 model). A link between the Th1 phenotype and ligand expression was not found in vivo. Surprisingly, the potentially regulatory IL‐10‐producing T cells displayed the highest frequency of ligand‐positive cells in general. Within the inflamed tissues, the frequencies of P‐selectin‐binding cells increased in the dominant subset, either Th1 or Th2. Up‐regulation was also found for E‐selectin ligands during influenza, but not Nippostrongylus infection. In conclusion, conditions driving T cell polarization into either Th1 or Th2 in vivo do not affect the expression of selectin ligands, but acquisition of P‐selectin binding and hence migration into inflamed tissues is boosted by an inflammatory milieu.