bluuebunny/crossref_metadata_2025 huggingface dataset:
Phospholipid coatings for the prevention of membrane fouling
Authors: Reuben Bryan G. , Perl Orly , Morgan Neil L. , Stratford Peter , Dudley Linda Y. , Hawes Christopher
Published: May 2005

The aim of the present work was the development of phosphorylcholine‐based treatments for biofiltration membranes and the demonstration that such treatments prevent or inhibit protein fouling. Microfiltration membranes of cellulose triacetate, polyether sulphone and polyvinylidene fluoride were etched with oxygen in a plasma chamber to generate surface hydroxyl groups and were then treated with the monomer 2‐methacryloyloxyethyl phosphorylcholine. These membranes were evaluated with water, buffer, bovine serum albumin (BSA), yeast fermentation broth, beer and orange juice. The treatment of cellulose triacetate membranes reduced both the initial flux and the extent of water fouling. In terms of the integrated flux, these factors tended to cancel each other out. For protein, the membranes gave similar or higher fluxes but worse fouling. The cellular feed (yeast) reacted more favourably to the coating than the BSA. The polyether sulphone was scarcely affected by the coating; fouling remaining high with most ‘real’ feeds. There was lower initial flux but less flux decline with water and beer. Washing with water and cleaning with Tergazyme did not restore the initial flux. Polyvinylidene fluoride membranes gave the most positive results. In most cases, the coating both increased initial flux and decreased the rate of fouling. The coating was particularly effective for BSA and for beer and orange juice, where fouling is probably caused by a polysaccharide rather than by a protein. Electron microscopy showed, nonetheless, that fouling by proteins was accompanied by protein adsorption primarily on the upper surface of the membrane and that coated membranes showed less deposition and in different places than did untreated membranes.
Enhancement of uranium bioaccumulation by a Citrobacter sp. via enzymically‐mediated growth of polycrystalline NH4UO2PO4
Authors: Yong Ping , Macaskie Lynne E.
Published: May 2005

The objective of this work was to study the effect of pH and ionic matrix on product release and on the removal of uranyl ion by a Citrobacter. sp phosphatase enzyme‐catalysed reaction. An improvement in the efficiency of uranyl removal was obtained by incorporating ammonium acetate (NH4Ac) into the solution. It was confirmed using X‐ray diffraction (XRD), and other analytical techniques, that the insoluble, cell‐bound product was NH4UO2PO4.
Optimisation of the fibre production system used for the immobilisation of Saccharomyces cerevisiae employed in the production of NADH in a novel bioreactor
Authors: Stevenson Eileen C. , McNally Gerry M. , Spedding Peter L.
Published: May 2005

Saccharomyces cerevisiae was immobilised in wet spun calcium alginate fibres for use in a bioreactor as an immobilised catalyst. The actual fibre production system was studied to determine optimum conditions when the fibre was used in the NADH reaction. The extrusion pressure and fibre winding speed were identified as the important variables and were optimised at 0·4 bar (g) and 300 rpm respectively. Other variables had little effect on the efficiency of the whole system.
Oxidative coupling of methane to C2‐hydrocarbons over lithium–cerium‐promoted MgO and MgO–CaO catalysts
Authors: Tiwari Kaushal K. , Roy Tarak N. , Banerjee Somnath , Ganguly Subrato , Bhattacharyya Deba P.
Published: May 2005

The oxidative coupling of methane to ethylene and ethane was studied over lithium–cerium‐promoted MgO and MgO–CaO catalysts in the presence of molecular oxygen at 730°C and at atmospheric pressure in a continuous flow, fixed bed quartz reactor. The catalysts were prepared by an impregnation method and finally calcined at 900°C. The surface area, pore size distribution and pore volume of the catalysts were determined. The feed consisted of only methane and oxygen in the molar ratio of 2:1. The results obtained over the catalyst systems, viz. (i) lithium–cerium‐promoted MgO and (ii) lithium–cerium‐promoted MgO–CaO, have been compared. A relatively high C2‐selectivity has been obtained with Li–Ce‐promoted MgO–CaO catalysts. The optimum yield and selectivity for C2‐hydrocarbons were found to be 21·5% and 76·8% respectively at a methane conversion of 28% over Li (7 wt%)–Ce (2 wt%)‐doped MgO–CaO (3:1 wt ratio) catalyst. The various factors governing the activity and the selectivity of the catalyst systems have been discussed.
Interfacial activity and rate of palladium(II) extraction with decyl pyridine monocarboxylates
Authors: Wiśniewski Maciej , Jakubiak Artur , Szymanowski Jan
Published: May 2005

Decyl isonicotiniate and decyl nicotiniate permit a rapid extraction of palladium(II) from its hydrochloride solutions. Decyl picoliniate is not a suitable extractant. 4‐Octylphenylamine can act as a phase transfer catalyst when its concentration in the organic phase is at least 2·5 × 10−4 M. It seems that the interfacial adsorption of pyridine carboxylates and of 4‐octylphenylamine is not the decisive phenomenon in palladium(II) extraction. The negligible protonation of the pyridine‐type extractants and the phase transfer catalysis explains well the quick extraction of palladium(II) with the commercial and highly hydrophobic extractant ACORGA CLX‐50.
Production of the fungal exopolysaccharide scleroglucan by cultivation of Sclerotium glucanicum in an airlift reactor with an external loop
Authors: Wang Yuchun , McNeil Brian
Published: May 2005

Sclerotium glucanicum NRRL 3006 was cultivated in a 120 dm3 working volume airlift reactor with external recirculation loop for the production of the exopolysaccharide (EPS), scleroglucan. When culture pH was not controlled EPS production, at a range of air flow rates, was poor (<2 kg m−3). Biomass formation generally increased with increasing aeration rate. When culture pH was controlled at 4·5 ± 0·2 EPS production was maximal at an air flow rate of 100 dm3 min−1 and fell as air flow rate decreased. Operation of the reactor at a high (100 dm3 min−1) air flow rate for the early part of the process (up to 96 h), followed by a low air flow rate (20 dm3 min−1), led to reduced biomass and oxalate formation, and a slight increase in EPS concentration relative to operation at a constant air flow rate of 100 dm3 min−1. EPS production in this pneumatically‐agitated reactor was equal to the highest levels reported in small‐scale stirred tank reactors.
Photostabilisation of colour formers for heat‐sensitive recording systems: Effect of counter‐ions on the photofading of fluoran dyes
Authors: Oda Hironori
Published: May 2005

Fluorans are given considerable attention as functional dyes for heat‐and/or pressure‐sensitive recording media. Numerous potential metal complexes were synthesised to prolong the life of coloured species. The protecting effect of these compounds against the photofading was examined on cellulose. It was found that the zinc or nickel salts of 3,5‐dihydroxy‐2‐naphthoic acid and its derivatives can be applied as effective stabilisers against the fading of fluoran dyes.
Pepsin immobilised by covalent binding to a chitosan derivative
Authors: González Gustavo , Alea Jacqueline
Published: May 2005

An insoluble active preparation of pepsin was made by covalent binding of the enzyme to succinylated chitosan through amide bond formation, with carbodiimide as condensing agent. The enzyme retained 80% specific activity and showed greater stability on storage than the soluble enzyme.
Cloning, expression and characterisation of a single‐chain antibody fragment to the herbicide paraquat
Authors: Graham Barbara M. , Porter Andy J. R. , Harris William J.
Published: May 2005

New cost effective methods for the detection and removal of pesticides from water samples are required to meet modern safety standards. The recent development of techniques to produce antibody fragments in bacteria has provided the opportunity to exploit antibodies as specialised chemicals for affinity detection/removal technologies. The variable heavy and light polypeptide chains of the anti‐paraquat monoclonal antibody PQXB1/2 have been cloned into the single‐chain antibody (ScAb) expression vector pBG1. The construct was expressed in Escherichia coli and 0·4 mg functional antibody produced from 1 dm3 of induced culture. Characterisation of ScAb by antigen binding profile and competition ELISA showed it to have a sensitivity one order of magnitude below that of the parent monoclonal. ScAb was purified as a monomer or dimer and analysed by HPLC size exclusion chromatography. When immobilised on polystyrene beads the ScAb could remove 85% of a paraquat–bovine serum albumin conjugate from solution in a single step.
Reaction of thioxanthen‐9‐one with the superoxide anion in an aqueous system containing dodecyltrimethylammonium bromide
Authors: Duty Robert C. , Carothers Larry D. , Roark Robin , Sahni Irvine
Published: May 2005

This research deals with the oxidation of thioxanthen‐9‐one with the superoxide anion to the sulfoxide and to the sulfone. We were also interested in determining whether the thioxanthen‐9‐one could be oxidized further to carbon dioxide. The experiments revealed that no carbon dioxide was formed from the oxidation of thioxanthen‐9‐one. However, it was found that carbon dioxide was formed from the anode reacting with the superoxide anion.
Kinetics of addition of acetic acid to epichlorohydrin in the presence of alkali metal acetates
Authors: Bukowska Agnieszka , Guskov Andrei K. , Makarov Mikhail G. , Rokaszewski Edward , Svets Valery F
Published: May 2005

The kinetics of the reaction between acetic acid and epichlorohydrin in the presence of lithium, sodium and potassium acetates have been studied. The composition of the reaction mixture was followed chromatographically. Beside the two isomeric products of addition of epichlorohydrin to acetic acid, the presence was found of glycidyl acetate, glycerine dichlorohydrin and other products of parallel and subsequent reactions between the substrates and chlorohydroxyesters. A mechanism of the reaction, which takes into account the formation of the identified compounds has been proposed and a set of appropriate differential and balance equations developed. The rate constants for individual reactions as well as the catalysts used have been determined.
A novel way to treat refractory waste: Sonication followed by wet oxidation (SONIWO)
Authors: Ingale Muralidhar N. , Mahajani Vijaykumar V.
Published: May 2005

The effectiveness of the hybrid system sonication followed by wet oxidation (SONIWO) to treat otherwise refractory waste has been demonstrated. In such a hybrid system homogeneous CuSO4 catalyst was found to be very efficient.
Onset of gas self‐induction and power consumption after gas induction in an agitated tank
Authors: Hsu Yung Chien , Chang Hung‐Ch'i
Published: May 2005

The behavior of inducted gas from liquid surface and the; power requirements in an agitated tank using a mechanical agitator are studied in order to increase the amount of gas self‐induction and the gas retention time for gas absorption. A 45° six‐blade downward impeller turbine was utilized in this study. Air and water, air and 40 wt% 60 wt%, and 80 wt% of glycerin water, and air and 106 cP silicon oil were employed as gas and liquid phases. Variables which were studied included geometrical factors (immersed depth of impeller, baffle with and diameter of impeller) and the physical properties of the liquid (viscosity, density, and surface tension). The correlations for the onset speed of impeller and power consumption after gas induction in the agitated tank are established from our experimental results. The amount of gas self‐induction from the liquid surface in the agitated tank increases with increasing impeller diameter and speed and decreases with increasing baffle width, depth of impeller and viscosity of liquid.
A study of fluid dispersion in oscillatory flow through a baffled tube
Authors: Ni Xiongewei
Published: May 2005

Previous studies show that axial dispersion in steady laminar flow can be substantially reduced by superimposing fluid oscillation in a baffled tube. In this paper, experimental observations on fluid dispersion for oscillatory flow in a baffled tube are obtained in a series of concentration measurements using high spatial resolution local conductivity probes, and two models—the continuous stirred tank (CST) with feedback and the plug flow with axial dispersion—are used to analyse the concentration curves and determine the fluid dispersion for such a system. The CST with feedback model combines the algorithms from Mecklenburgh and Hartland with the evaluations of unbiased moments from Anderssen and White to determine the dimensionless dispersion coefficient, D/uL, and the backmixing coefficient, F. The plug flow with axial dispersion model, on the other hand, utilises the axial diffusion model by replacing the molecular diffusion coefficient to the axial dispersion coefficient. This model uses an upstream concentration measurement together with an imperfect pulse technique to predict a downstream concentration profile, and thereby determine a best fit value for the dispersion coefficient D/uL. The axial dispersion results show that there is generally more dispersion predicted using the plug flow with axial dispersion model than when using the CST with feedback model for all the oscillatory Reynolds numbers and Strouhal numbers tested. The difference in the calculated D/uL between the two models is discussed.
Immobilization of glucose oxidase in the regenerated silk fibroin membrane: Characterization of the membrane structure and its application to an amperometric glucose sensor employing ferrocene as electron shuttle
Authors: Liu Yongcheng , Yu Tongyin , Liu Haiying , Qian Jianghong , Deng Jiaqi
Published: May 2005

The structural changes of the regenerated silk fibroin membranes for immobilizing glucose oxidase were characterized with FT‐IR spectra. The results of electronic absorption spectra and scanning electron microscopy illustrated that the glucose oxidase in the membranes existed in aggregates. The blend membranes exhibited an island‐like structure, attributable to the incompatible and weak intermolecular interactions between regenerated silk fibroin and glucose oxidase. The glucose sensor was constructed by combining glucose oxidase immobilized in regenerated silk fibroin membrane with an Eastman‐AQ‐ferrocene modified electrode. The advantages of the mediator include high stability and the ability to use a less positive potential for increased selectivity.
Kinetics of formation of diphenoxymethane from phenol and dichloromethane using phase‐transfer catalysis
Authors: Wu Ho‐Shing , Jou Sung‐Hauh
Published: May 2005

The reactions of phenol with dichloromethane using quaternary ammonium salts as a liquid–liquid phase‐transfer catalyst in an organic solvent/alkaline solution were investigated. The technique of phase‐transfer catalysis had a dramatic accelerating effect on the reaction and increased the yield of diphenoxymethane by more than 95%. The effects of catalysts, temperature, and basic concentration on reaction rate were studied in order to find the optimum operating conditions for this reaction. Experimental results indicated that a potassium hydroxide was preferred over sodium hydroxide in order to enhance the reactivity of the reaction. The reaction rate constant and the distribution coefficient of the intermediate product were obtained. During the reaction, the concentration of the intermediate product was also measured in order to study its behavior in the liquid–liquid system.
Production of salicylate hydroxylase fromPseudomonas putidaUUC‐1 and its application in the construction of a biosensor
Authors: Zhou Dao‐Min , Nigam Poonam , Jones John , Marchant Roger
Published: May 2005

The enzyme salicylate hydroxylase was produced fromPseudomonas putidaUUC‐1 in an 80 dm316 h batch fermentation process yielding, ∼ 9 K units per 60 dm3. This enzyme preparation has been studied for its application in the construction of biosensor systems, e.g. carbon past electrodes, screen‐printed carbon electrodes, and disposable carbon enzyme electrodes, which will be used for the rapid estimation of salicylate in blood sample. The linear range of the disposable carbon enzyme electrode in response to salicylate was achieved to 1·8 mmol dm−3.
Stabilization of cell biocatalyst with β‐galactosidase activity by glutaradehyde treatment
Authors: Flores María V. , Voget Claudio E. , Ertola Rodolfo J. J.
Published: May 2005

In the present study the stabilization with glutaraldehyde of permeabilized, non‐viable Kluvernomyces lactis cells with β‐galactosidas (β‐D‐galactosidase galactohydrolase, EC 3.21.23) activity has been investigated. The influence of various factors in relation to the glutaradehyde treatment, such as reaction time, temperature and glutaraldehyde and cell concentration, has been considered. The cell biocatalysts showed a good storage and operational stability. The kinetic properties of the biocatalyst in concentration with lactose hydrolysis were found to be comparable to the cell‐free enzyme.
Surface properties of magnesium oxide obtained from basic magnesium carbonate: Influence of preparation conditions of magnesium carbonate
Authors: Choudhary Vasant R. , Pataskar Suryakant G. , Zope Ganesh B. , Chaudhari Pravin N.
Published: May 2005

Surface area, total basicity and base strength distribution (weak, strong and intermediate strength basic sites) of magnesium oxide obtained from basic magnesium carbonate (by its decomposition at 873 K) prepared by precipitation using different magnesium slats, precipitating agents and precipitating conditions (viz. concentration of magnesium salt. pH, temperature, mode of mixing and ageing period) have been thoroughly investigated. The total basicity and base strength distribution of the different magnesium oxide samples have been determined by step‐wise thermal desorption of carbon dioxide from 323 to 1253 K. The chemical composition of basic magnesium carbonate and the surface properties and carbon dioxide content of magnesium oxide are found to be strongly influenced by the aforementioned preparation conditions of basic magnesium carbonate.
Capillary gas chromatography based on a capsule‐insertion technique. 1. General aspects and comparison with split‐injection systems
Authors: Buser H. U. , Widmer H. M.
Published: May 2005

A capsule‐insertion system tailored to the needs of capillary gas chromatography is described. It provides the basis for a truly quantitative and improved qualitative approach to open tubular capillary GLC. The advantages of the system lie in its simplicity of handling and in the possibility of using relatively low injection temperatures, thus reducing the risks to thermally unstable samples.

The observed high efficiencies characterizing this capillary GLC capsule technique allow full advantage to be taken of the operating capacity of the superior capillary columns to give a performance competitive with the best known split‐injection systems.
Supercritical fluid chromatography and some of its applications: A review
Authors: White C. M. , Houck R. K.
Published: May 2005

The general topic of supercritical fluid chromatography (SFC) is introduced, and historical aspects of its development are discussed. The physical properties of supercritical fluids, gases and liquids are tabulated. SFC is compared and contrasted with the classical forms of chromatography ‐ gas chromatography (GC) and high performance liquid chromatography (HPLC). The selectivity of SFC, GC, and HPLC are discussed and compared. Instrumentation employed for supercritical fluid chromatography is depicted. A wide variety of SFC applications are introduced. New examples of the use of SFC for analysis of a variety of complex oligomeric mixtures indcluding polypropylene glycol, polysiloxanes, fluorocarbon oligomers (i.e. ‐3M's fluoro‐chemical surfactant Fluorad 171, and Kel‐F) and high molecular weight normal alcohols are shown. The use of SFC for separation of mono‐, di‐, and triglycerides at low operating temperatures is described. Lastly, the use of SFC for separations of complex hydrocarbon mixtures from liquid fuels, polycyclic aromatic hydrocarbons, synthetic alpha‐olefins, and petroleum functional group separations are depicted.
Some aspects of quantification of neutral steroid metabolites in body fluids of healthy and uremic subjects by capillary gas chromatography
Authors: Ludwig‐Koehn H. , Henning H. V.
Published: May 2005

Neutral steroid metabolites enriched from urine and hemofiltrate were identified by gas chromatography/mass spectrometry and quantified by capillary gas chromatography. This study included 20 healthy controls and 37 uremic patients. Before enrichment of steroids from biological material, the standard deviation of the workup procedure and subsequent derivatization into the trimethylsilyl‐enol‐trimethylsilyl ethers was tested and found to be 2–5% in urine and 12–17% in the more complicated workup procedure of hemofiltrate, but essentially smaller than the biological standard deviation. Compared to the 24 h urinary excretion rates of controls, the excretion rates of androsterone, etiocholanolone, and corticoid metabolites were significantly lower in uremic body fluids, while those of 11‐oxygenated androstanolones, degradation products of corticoids, were enhanced in uremic urine. The ratio of corticoid metabolites to 11‐oxygenated androstanolones in urine of nondialyzed uremics correlated significantly with their plasma creatinine levels.
Acceleration of free release static coating of capillary columns by the presence of polar solvents in the coating solution – a theoretical study
Authors: Xu B. , Vermeulen N. P. E.
Published: May 2005

The cause of an observed acceleration in the free release static coating process of a capillary when more polar solvents are added to alkanes as stationary phase solvents has been studied. By using a computer program, 9 of the relevant physical parameers were calculated in relation to the composition of the solvent hixtures. Curves of these parameters vs composition of the mixures were drawn. From the results it can be deduced that the change of these parameters with the increase of polar solvents in the solution, is probably insufficient to explain the drastic increase of the free release static coating speed. A physical model is proposed to calculate the depth of the meniscus around which sufficient heat can be transferred into the evaporating surface per unit time, to evaporate the solvent at a rate that the coating speed indicates. It is demonstrated that when pentane‐acetone mixtures are used to coat a capillary, the depth of the meniscus indeed is greater than when pure pentane is used. The proposed model may lead to a better understanding of phenomena involved in the static coating process.
Considerations for analytical supercritical fluid extraction of sulfonyl ureas employing a modified fluid
Authors: Howard Angela L. , Taylor Larry T.
Published: May 2005

Important considerations are discussed for analytical SFE method development employing methanol–modified carbon dioxide and solid‐phase trapping. The focus of this study was to break the method development procedure into distinct steps so that the origins of low recoveries could be determined conclusively. Sulfonyl urea herbicides were used as probe analytes. Analyte solubility, analyte trapping, analyte trap removal (solid‐phase), and extract analysis were all shown to be equally important in achieving quantitative SFE recoveries.
Prediction of retention values in linear temperature programming of narrow and mega‐bore capillary columns
Authors: Gerbino Tomaso C. , Castello Gianrico
Published: May 2005

Retention times in linear temperature programmed gas chromatography on narrow bore and megabore capillary columns have been calculated from experimental retention times measured at three isothermal temperatures: an iterative procedure performed by BASIC programs was used to obtain the values of the constants enabling the calculation of the programmed temperature retention times. Different methods of calculation have been compared.
Supercritical fluid extraction of atrazine and its metabolites from soil
Authors: Alzaga Roberto , Bayona Josep M. , Barceló Damià
Published: May 2005

Soxhlet (methanol) and SFE extraction with carbon dioxide in the presence of modifiers at different temperatures (100–200°C) for the extraction of atrazine and its main metabolites from a soil sample were compared. The most effective extraction conditions for both atrazine and its metabolites (i.e.deethylatrazine and deisopropylatrazine) were Co2modified with 20% molar methanol‐trifluoroacetic acid (MeOH‐TFA) (TFA 0.65M in MeOH) at 100°C, leading to an extraction efficiency comparable with that of Soxhlet extraction with MeOH for atrazine andca.20% higher for its main metabolites. The relative standard deviation (RSD) of SFE was lower than that obtained by Soxhlet extraction, probably because of less interference in the cGC‐NPD determination. All the other modifiers evaluated (acetone, triethylamine, and methanol) were less effective than MeOH‐TFA for the extraction of atrazine and its metabolites from a soil sample, even at high molar concentrations (20%) and use of higher extraction temperatures (200°C). These results indicate the importance of matrix effects and the need of the selection of an appropriate modifier in order to obtain quantitative extractions by SFE.
Comparison of different heptakis(6‐O‐alkyldimethylsilyl‐2‐3‐di‐O‐ethyl)‐β‐cyclodextrins as chiral stationary phases in capillary GC
Authors: Kim Byoung Eog , Lee Kwang‐Pill , Park Keung‐Shik , Lee (deceased) Sun Haing , Park Jung Hag
Published: May 2005

Three new β‐cyclodextrin derivatives, heptakis(6‐O‐isopropyldi‐methylsilyl‐2,3‐di‐O‐ethyl)‐β‐cyclodextrin, heptakis(6‐O‐thexyldi‐methylsilyl‐2,3‐di‐O‐ethyl)‐β‐cyclodextrin, and heptakis(6‐O‐cy‐clohexyldimethyl‐2,3‐di‐O‐ethyl)‐β‐cyclodextrin (IPDE‐β‐CD, TXDE‐β‐CD, and CHDE‐β‐CD), were synthesized and the enan‐tioselectivities of these three CD derivatives and heptakis(6‐O‐tert‐butyldimethylsilyl‐2,3‐di‐O‐ethyl)‐β‐cyclodextrin (TBDE‐β‐CD) were compared for GC separation of a range of chiral test com‐pounds. In particular TXDE‐β‐CD showed much higher enentio‐selectivity than TBDE‐β‐CD. Enentioselectivities of IPDE‐β‐CD and CHDE‐β‐CD are somewhat lower than that of TXDE‐β‐CD and CHDE‐β‐Cd are somewhat lower than that of TXDE‐β‐CD. These observations are indicative of significant effects of subtle changes in the structure of the 6‐O‐substituent on the enantioselec‐tivity of the β‐CD derivatives. The difference in enantioselectivities of the 6‐O‐substituted CD derivatives were explained in terms of relative contributions of the effects of hydrophobicity and steric hindrance of the substituent to the inclusion process. CHDE‐β‐CD showed the lowest enantioselectivity among the threederivatives. It is likely that the unfavorable steric hindrance of the bulky cyclo‐hexyl group plays a greater role than the favorable hydrophobicity effect of the cyclohexyl group in the inclusion process in CHDE‐β‐CD. IPDE‐β‐CD showed lower selectivity than TXDE‐β‐CD and TBDE‐β‐CD. In the case of these CD derivatives having acyclic substituents the relative hydrophobicity of the substituent seems to be a dominant factor affecting the inclusion process. Isopropyl groups factor affecting the inclusion process. Isopropyl groups are less hydrophobic than thexyl and tert‐butyl groups.
Proposed interaction between insulin and retinoblastoma protein
Authors: Radulescu Razvan T. , Wendtner Clemens M.
Published: May 2005

Retinoblastoma protein (RB) is a tumor suppressor gene product involved in embryogenesis and cell cycle progression. One of the major mechanisms leading to RB dysfunction is complex formation with viral oncoproteins using the common RB binding motif Leu × Cys × Glu (LXCXE) which has also been identified in cellular ligands, e.g., RBP‐1 and RBP‐2. p107, a cellular protein with RB sequence homology, has been shown to bind to the same viral oncoproteins associating with RB and is therefore thought to contribute to cell cycle regulation. It has recently been suggested that insulin stimulates gene transcription through direct association with an, as yet, unidentified intracellular transcription factor. Due to the central roles of RB and p107 in coupling external growth signals with the progression of the cell cycle clock, we have hypothesized that these two proteins might be candidates for mediating the effects of insulin of DNA. We report here the identification of a region in the B‐chain of human insulin that has the sequence LXCXE. Based on this finding we predict that the insulin B‐chain may interact with RB and/or p107. Since we have also identified sequences hydropathically related to LXCXE in insulin‐like growth factor I (IGF‐I) and II (IGF‐II), but not in relaxin, nerve growth factor, epidermal growth factor, glucagon or β‐endorphin, we further proposed that both IGF‐I and ‐II may assemble with RB and / or p107, too. Moreover, binding sites on RB and p107 identical with those suggested for viral oncoproteins and cellular ligands are predicted for insulin/IGF‐I/IGF‐II by using the hydropathic complementarity approach. Our proposal of associations between insulin/IGF‐I/IGF‐II and RB/p107 might be important for the understanding of cell growth regulation.
Plasticity of the serotonergic innervation of the dorsal horn of the rat spinal cord following neonatal capsaicin treatment
Authors: Marlier L. , Poulat P. , Rajaofetra N. , Sandillon F. , Privat A.
Published: May 2005

Neonatal capsaicin treatments (25 or 50 mg/kg, 12, 24, or 48 hr after birth given subcutaneously) were applied in order to follow by immunocytochemical techniques the postnatal development and plasticity of the Serotonergic system in the dorsal horn of the rat spinal cord. Two markers of the lesions of C primary afferents induced by capsaicin were tested by immunocytochemical detection: substance P and cal‐citonin gene‐related peptide (CGRP). We show that the internal part of substantia gelatinosa (lamina Ili) which does not contain Serotonergic fibers in intact or vehicle‐treated rats is invaded within a few days after capsaicin treatment by Serotonergic fibers apparently sprouting from the deepest laminae. Moreover, these fibers often establish axodendritic synapses while synapses are rare in intact animals in the whole dorsal horn. This reorganization is stable whatever the dose of capsaicin used or the moment chosen for its injection. On the other hand, while lesions of substance P‐ergic fibers appeared quite stable, partial recovery of CGRP innervation was found after 3 to 6 months, especially with the low dose of capsaicin. We discuss the ability of the Serotonergic system innervating the dorsal cord either to find new targets or to fill vacated sites when one of its putative targets is removed.
Axonal regeneration of an identified Helisoma neuron depends on the site of axotomy
Authors: Kruk P. J. , Bulloch A. G. M.
Published: May 2005

Axotomy or molluscan neurons usually results in axonal regeneration. In this study, we tested the axotomy response of an identified neuron of the pond snail Helisoma trivolvis (buccal neuron 4, B4). This neuron has two primary axonal branches, the ipsilateral axon and the contralateral axon, each innervating one of the paired salivary glands. The ipsilateral axon projects via the ipsilateral esophageal nerve trunk whereas the contralateral axon crosses both buccal ganglia and projects via the contralateral esophageal nerve trunk. We tested various procedures of axotomy: injury to one axon or both axons, close to the ganglion or more distal. Surprisingly, we found that proximal axotomy of the ipsilateral axon was not usually followed by axonal regeneration. By contrast, all other procedures of axotomy (e.g., distal ipsilateral, or proximal bilateral) resulted in robust axonal regeneration and target reinnervation. Thus, in this preparation, axotomy may or may not result in axonal regeneration, depending on the site(s) of axotomy. To the best of our knowledge, such a differential result has not yet been found in any other preparation. We conclude that axotomy is not always a sufficient condition for axonal regeneration of molluscan neurons. We hypothesize that a damaged axonal stump may be a necessary condition for the initiation of regeneration. An alternative hypothesis is that neurite outgrowth is inhibited in normal mature neurons by a target‐derived factor. This hypothetical factor would be transported retrogradely, but not anterogradely, along axons.
Alterations of 45Ca accumulation and [3H] inositol 1,4,5‐trisphosphate binding using autoradiography in the exo‐focal postischemic brain areas of the rat
Authors: Nagasawa H. , Kogure K.
Published: May 2005

We studied the alterations of calcium accumulation and intracellular signal transduction using autoradiography of the second messenger system in order to clarify the mechanisms of the delayed neuronal changes in the remote areas of rat brain after transient focal ischemia. Chronological changes of 45Ca accumulation and [3H] inositol 1,4,5‐trisphosphate (IP3) binding sites were determined after 90 min of right middle cerebral artery (MCA) occlusion and after such occlusion followed by different periods of recirculation. After the ischemic insult, 45Ca accumulation extended to the lateral segment of the caudate putamen and to the cerebral cortex, both supplied by the occluded MCA. One day after the ischemia, [3H]IP binding sites decreased significantly compared with the control values in these ischemic areas. Moreover, 3 days after the ischemia, 45 Ca accumulation was first detected in the ipsilateral thalamus and the substantia nigra, which lay outside the ischemic areas. In the substantia nigra, a significant decrease of [3H]IP3 binding sites and concurrent 45Ca accumulation were observed. In the thalamus, however, there was no alteration until 1 week after the ischemia, and then [3H]IP3 binding sites increased significantly 2 weeks (P < 0.05) and 4 weeks (P < 0.01) after the ischemia. Based on the present study, we speculate that different mechanisms associated with signal transduction systems may be responsible for exo‐focal postischemic delayed neuronal changes in the thalamus and the substantia nigra. The increase of [3H]IP3 binding sites of the thalamus in the chronic stage may be new evidence of plasticity related to neurotransmission.
Peanut agglutinin binding glycoproteins in the chick retina: Their presence in Müller glia cells
Authors: Arregui C. , Barra H. S. , Landa C. A.
Published: May 2005

The histological and cellular distribution and some biochemical characteristics of components that bind peanut agglutinin (PNA), a lectin that recognizes preferentially terminal galactose‐β (1–3) N‐acetyl galactosamine disaccharide residues of glycoconjugates, were studied in chick retinal tissue and in dissociated retinal cells after their differentiation in culture. In sections of retinal tissue from animals 7 days after hatching (Rp7), in addition to the inner and outer segments of the photoreceptor layer, the plexiform and optic fiber layers were stained with rhodamine‐labeled PNA, indicating that, besides photoreceptor cells, other cellular types contribute to the PNA staining. We present evidence indicating that at least part of this staining is provided by Müller glia cells. In cultures of dissociated cells from retinas at embryonic day 7 (R7), photoreceptor‐like cells and flat Müller glia‐derived cells but not neurons were stained with rhodamine‐labeled PNA. Furthermore, Müller glia cells isolated from Rp7 were also brightly stained with PNA. Western blot assays of extracts from R7 showed the presence of PNA binding glycoproteins of 31–33 kDa and a component that migrates at the dye front. In addition to the components detected in R7, extracts from R14 and Rp7 showed the presence of a major PNA binding glycoprotein of 175 kDa and a minor glycoprotein of 220 kDa. Extracts from the photoreceptor layer contain the 175 and 220 kDa glycoproteins, indicating their association with photoreceptor cells. The 31–33 kDa components were detected in extracts from the remnant inner retina, suggesting their association with the Müller glia cells. Supporting this view, these components and not those of 175 and 220 kDa were detected in cell cultures enriched in flat Müller glia‐derived cells. Only the 31–33 kDa components and the component that migrates at the dye front were detected in extracts from cell cultures enriched in photoreceptor‐like cells, suggesting the need of some environmental element for the expression of the 175 and 220 kDa components in the differentiated photoreceptor cells.
Heptyl‐physostigmine enhances basal forebrain control of cortical cerebral blood flow
Authors: Linville D. G. , Giacobini E. , Arnerić S. P.
Published: May 2005

This study sought to determine the effect of heptylphysostigmine (H‐PHY), a reversible cholinesterase (ChE) inhibitor with greater lipophilicity and longer duration of action than physostigmine, on resting and basal forebrain (BF)‐elicited increases in cortical cerebral blood flow (CBF). Laser‐doppler flowmetry (LDF) was used to monitor changes in frontal cortical microvascular perfusion in urethane anesthetized rats. Responses were measured before, early after, and 1 hr following H‐PHY, 3 mg/kg, i.m. Electrical stimulation (100 μA) of the BF elicited up to 220% increases in CBF at 50 Hz, an effect that was graded with frequency. At 15 min following H‐PHY (3 mg/ kg) resting cortical CBF was unchanged, whereas BF‐elicited increases were potentiated 47% at 50 Hz. At 1 hour, resting cortical CBF remained unchanged, and the BF‐elicited responses were remarkably potentiated by 354% at 10 Hz and 67% at 50 Hz. Acetylcholinesterase (AChE) activity measured in the tissue directly beneath the LDF probe was decreased by 84% at a time when these CBF responses were enhanced. These data suggest that H‐PHY substantially enhances the regulation of cortical CBF by the BF, an effect that may be linked to inhibition of cortical AChE activity. This enhancement of cortical CBF may contribute to the efficacy of H‐PHY as a treatment for Alzheimer' disease.
Transient, cyclic changes in mouse visual cell gene products during the light‐dark cycle
Authors: McGinnis J. F. , Whelan J. P. , Donoso L. A.
Published: May 2005

Temporal and spatial changes in the cellular and sub‐cellular concentrations of photoreceptor cell gene products appear to be important features of pho‐totransduction in rod photoreceptor cells. The time course of the rapid, light‐dependent movement of S‐antigen (S‐Ag) (48k; Arrestin) from the inner segments to the outer segments was analyzed using poly‐clonal and monoclonal antibodies. The concentrations of mRNA change about threefold for rhodopsin and about sixfold for S‐Ag in cyclic, independent modes during the normal light‐dark cycle. Kinetic analysis indicates that the oscillations of S‐Ag mRNA levels are due to changes in the transcriptional activity of the gene itself. An experimental model is presented summarizing the relationships between mRNA levels, protein localization, disc shedding, and phototransduction in the photoreceptors cells.
Purified cultures of keratin‐positive olfactory epithelial cells: Identification of a subset as neuronal supporting (Sustentacular) cells
Authors: Pixley S. K.
Published: May 2005

The mammalian olfactory neuroepithelium, lining part of the nasal cavity, retains into adulthood progenitor cells for the olfactory receptor neurons and other cell types in the epithelium. The details of cellular lineage relationships are not completely under stood. In particular, the exact nature of the interactions between several progenitor cell types and their relationship to neurons is not known. Studies of this system have been hampered by the lack of cell culture models and insufficient cell‐type‐specific markers. Antibodies to the cytokeratins are fairly specific markers for one potential progenitor cell type, the dark basal cells of the olfactory epithelium. Keratin immunostaining was used to develop cell culture systems which contained large numbers of putative dark basal cells, using the soft nasal mucosal tissues of both newborn and adult rats. Media and substrate conditions were optimized. The conditions which sup ported growth of keratin‐positive nasal cells for greater than one month, and allowed partial purification, suggested similarities between olfactory and skin keratinocytes. Immunostaining with a monoclonal antibody specific for sustentacular cells (SUS‐1) showed a subset of these cells present in culture, with some cells double‐labelled with anti‐keratin. This staining confirms the olfactory origin of at least a subset of the cells, and supports the proposal that the majority of cells were the dark olfactory basal cells. This culture system gives novel insights into olfactory epithelial cell physiology, and allows culture of these cells for further studies examining regulation of differentiation.
Calcium‐activated neutral proteinase (calpain) activity in C6 cell line: Compartmentation of μ and m calpain
Authors: Banik N. L. , Chakrabarti A. K. , Konat G. W. , Gantt‐Wilford G. , Hogan E. L.
Published: May 2005

Calcium‐activated neutral proteinase (calpain) activity was determined, including in cytosol and membrane fractions, in rat glioma C6 cell line. The μ and m forms of calpain were separated by DEAE and phenylsepharose column chromatography and with removal of the endogenous inhibitor calpastatin. C6 cells contained more mcalpain than the μ isoform. More than 70% of mcalpain activity was membrane‐associated and 20% was cytosolic. Isolated plasma membrane also contained 69% of the mcalpain activity. In contrast, approximately 80% of μcalpain activity was cytosolic and 16% was membranous. Half‐maximal activity for μ and mcalpain was obtained at 1 μM and 0.2 mM CaCl2, respectively. Trypsin dissociation of cells reduced activity. Triton X‐100 stimulated mcalpain activity of the whole homogenate and the membrane pellet but not of the cytosol. Activity of the myelin marker enzyme adenosine 2′3′‐cyclic nucleotide 3′‐phosphohydrolase (CNPase), was also found in C6 cells. The identification of calpain and CNPase in C6 cells is in keeping with an interpretation that C6 differentiation resembles, at least in part, that of the myelin‐forming oligodendroglial cells.
Decorin, a chondroitin/dermatan sulfate proteoglycan is under neural control in rat skeletal muscle
Authors: Brandan E. , Fuentes M. E. , Andrade W.
Published: May 2005

Proteglycans (PGs) are abundant components of the extracellular matrices (ECM) of skeletal muscle. We have previously found that the synthesis of skeletal muscle PGs present at the ECM increase after denervation. The experiments reported here were undertaken to identify which PG(s) increase after denervation of rat leg muscles. Incorporation of ra‐dioactive sulfate demonstrated the presence of a chondroitin/dermatan sulfate PG of 70–90 kDa in the skeletal muscle ECM, which increased after denervation. The PG has a core protein of 39–45 kDa after treatment with chondroitinase ABC. Antibodies against rat decorin, a chondroitin/dermatan sulfate PG synthesized by various cell types, specifically immunoprecipitated this PG from a mixture of PGs. Immunocytolocalization of this PG indicated that the chondroitin/dermatan sulfate PG accumulates at the perimysium of skeletal muscle after denervation. Finally, Northern blot analysis indicated an increase of muscle transcripts for decorin after denervation. The data reported here suggest that a chondroitin/dermatan sulfate PG present at the skeletal muscle ECM, very similar if not identical to decorin, increases after denervation. © 1992 Wiley‐Liss, Inc.
Oligodendrocyte‐substratum adhesion activates the synthesis of specific lipid species involved in cell signaling
Authors: Vartanian T. , Szuchet S. , Dawson Glyn
Published: May 2005

Ovine oligodendrocytes (OLGs) undergo biochemical and morphological changes following attachment to polylysine. Autoradiographs of two‐dimensional thin‐layer chromatograms of [14H]Gal‐labeled OLG cultures revealed that attachment of OLGs to a polylysine substratum and their subsequent morphological differentiation is accompanied by an increased synthesis of multiple forms of galactosylceramide, sulfogalactosylceramide, and both sulfogalactosyl‐ and galactosyl‐diglycerides, together with an array of complex sialoglycosphingolipids, predominantly GM2 ganglioside. As previously reported, overall lipid synthesis measured by [14C]acetate incorporation into glycerophosphatides, sphingomyelin, and neutral lipids also increased dramatically for up to 60 days (last time point examined) following OLG‐substratum adhesion, reflecting membrane growth. Attachment was associated with a rapid augmentation in the synthesis of ethanolamine plasmalogen from 12 to 27% within 24 hr to reach a 35% plateau at 30 days and remain constant thereafter. In contrast, the plasmalogen content of phosphatidylcholine remained constant at 3–5%. This rapid increase in lipid synthesis (especially in the ethanolamine plasmalogen content following attachment) closely paralleled increased diacylglycerol (DAG) production and protein kinase C‐dependent phosphorylation of both myelin basic protein and 2′,3′‐cyclic nucleotide phosphohydrolase. Labeling studies indicated that the major source of [3H]arachidonate‐labeled DAG following attachment was from phosphatidylinositol turnover (and to a lesser extent phosphatidylcholine) rather than polyphosphoinositides or plasmalogens. Enhanced lipid synthesis is not only required for the production of membranes in these myelin‐producing cells but is also a source of second messengers required in the posttranslational modification of key myelin and cellular proteins. © 1992 Wiley‐Liss, Inc.
Transcriptional regulation of glial fibrillary acidic protein (GFAP)‐mRNA expression during postnatal development of mouse brain
Authors: Riol H. , Fages C. , Tardy M.
Published: May 2005

During mouse brain maturation, GFAP‐mRNA undergoes a two‐step developmental expression. It increases between birth and day 15 (period of astrocytic proliferation) and then decreases until day 55 (period of astrocytic morphological differentiation). We have developed an in vitro transcription procedure, as a mean to study the part of transcriptional control in this biphasic expression. After RNA synthesis by endogenous RNA polymerases in nuclei isolated from mouse brain (of 3 to 55 days and 217 days), the relative rates of GFAP‐mRNA transcripts were analysed by hybridization with a specific cDNA probe. As early as 3 days after birth, the rate of GFAP‐mRNA transcripts was maximal, whereas unexpectedly, it showed a significant decrease in mice of 15 days and stayed low until the 55th day. Therefore, a transcriptional control may take place early in mouse brain postnatal development by increasing the transcriptional rate of the GFAP gene in astrocytes, and during the transition from proliferation to differentiation phase of astrocytes (that occurs at the 15th day after birth) by decreasing this rate. However, posttranscriptional events may also occur to modulate the level of the cytoplasmic GFAP‐mRNA. In older mice (217 days), the low rate of GFAP‐mRNA transcripts found is not concordant with the high cytoplasmic level generally observed in gliosis of the aging brain. Our data suggest posttranscriptional events at this age. © 1992 Wiley‐Liss, Inc.