bluuebunny/crossref_metadata_2025 huggingface dataset:
Timing of odontogenic neural crest cell migration and tooth‐forming capability in mice
Authors: Zhang Yanding , Wang Shusheng , Song Yiqiang , Han Jun , Chai Yang , Chen YiPing
Published: March 2003

The mammalian tooth develops through sequential and reciprocal interactions between cranial neural crest (CNC)‐ derived ectomesenchymal cells and the stomadial epithelium. Classic tissue recombination studies demonstrated that premigratory CNC cells and CNC‐derived ectomesenchymal cells possess odontogenic capacity and can respond to oral epithelial signals to form a tooth, suggesting that the CNC cells contributing to odontogenic tissue are not prespecified. Here we show that, in mice, CNC cells have populated the forming first branchial arch before the 9‐somite stage and continue to migrate into the arch by the 13‐somite stage. Grafts of the first arch from the 10‐somite embryo or earlier yielded membranous bone and cysts but no teeth after subrenal culture. However, grafts of the first arch with its dorsally adjacent tissue containing migrating neural crest cells from the same age embryos gave rise to teeth. In contrast, teeth formed in first arch grafts that do not contain migrating neural crest cells from embryos with 12 or more somites. Interestingly, the acquisition of tooth forming capability in the first arch coincides with the onset of Fgf8 expression in the oral epithelium. These results suggest that there exists a population of odontogenic neural crest cells that migrates into the first arch between the 10‐ and 12‐somite stages. These cells either possess odontogenic potential and are able to initiate tooth development, or can respond to odontogenic signals derived from the oral epithelium to support tooth formation. Developmental Dynamics, 2003. © 2003 Wiley‐Liss, Inc.
A study of a new selective cell discard scheme with two threshold control on ATM networks
Authors: Sugizaki Yoshio , Asatani Koichi
Published: March 2003

When UBR (Unspecified Bit Rate) service is used on an ATM network, cells are discarded in congestion and imperfect packets are generated that consume network resources in a wasteful manner. As a remedy, the EPD (Early Packet Discard) control is proposed, in which the cells are discarded on a packet basis in congestion by providing a threshold to the input buffer. However, with EDP control, there is a possibility that the EOP (End Of Packet) cell in AAL5 may be discarded. Thus, two successive packets become invalid. For this reason, the TT‐EPD (Two Threshold‐EPD) that prevents discarding of the EOP cell has been proposed. This scheme sets two threshold values (TH1 and TH2) and the fixed TH1 works similarly to EPD control. TH2 carries out dynamic control and secures the input region for the EOP cell in the buffer. In this scheme, the amount of buffer between TH1 and TH2 decreases and there is an increase in the number of acceptance failures in which the cells composing a packet initially accepted are discarded by TH2. In this paper, a method that keeps the amount of buffer between TH1 and TH2 constant to reduce the acceptance missing packets is proposed. The effectiveness of the proposed scheme is demonstrated by simulation. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(8): 50– 57, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10039
A method for measuring the reflection coefficient of materials using a spatial spherical standing wave
Authors: Hiraike Taro , Saegusa Kenji , Hasebe Nozomu
Published: March 2003

When the measurement wavelength becomes longer, it becomes difficult to maintain a sufficient measurement space in the spatial standing wave method used for reflection coefficient measurement of electromagnetic wave absorbers. To date, a reflection coefficient measurement method using a spherical wave within a rather narrow space has been proposed. However, no theoretical verification has been carried out. In this paper, the spatial standing wave is analyzed by the physical optics approximation (PO) and the FDTD method when the distance between the transmitting antenna and the measuring material is set in the Fresnel region. The analytical results are compared with the experimental results. When a conductive plate is utilized as measuring material, the spatial standing wave distributions analyzed by PO and FDTD method, the measured distributions correlate well in terms of their tendencies. From experiments carried out with several types of electromagnetic wave absorbers at 600 to 2000 MHz, it is found that the reflection coefficient of the material can be determined by the spatial standing wave at about 1 to 2.5 wavelengths in front of the material. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(8): 40–49, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10081
A software antenna configuration having robustness for strong interference signal that arrives suddenly—Utilizing the power inversion characteristics in the second eigenvector beam output
Authors: Hatanaka Yoshitaka , Karasawa Yoshio
Published: March 2003

An environment is assumed in which a strong interference wave is suddenly incident. To produce an antenna robust to such an environment, a method is proposed in which an eigenvector beamspace adaptive array (EBAA) is formed by using the weight of the eigenvector for the first eigenvalue in the case of weak interference, but the weight of the eigenvector for the second eigenvalue in the case of strong interference. The performance of the interference suppression in the latter case (desired wave power ≪ interference wave power) is analyzed by numerical calculations and simulations. Also, this EBAA is superior in terms of configuration and performance to the well‐known power inversion adaptive array (PIAA). Based on the results, a software antenna configuration method for real‐time understanding of the propagation environment and adaptive switching of the algorithm is discussed. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(8): 20–28, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10099
Proposal and evaluation of multistage distributed traffic monitoring system
Authors: Kanamura Akira , Ohta Kohei , Waizumi Yuji , Kato Nei , Nemoto Yoshiaki
Published: March 2003

For network management, collection methods of administrative information based on traffic monitoring have been used widely. However, in a network that is divided into segments by switches and routers, different traffic is observed for each segment, so that there is a difference in the fault detection capability using the threshold mechanism and the collection of sufficient administrative information by packet analysis may not be possible. In this paper, the effects of network segmentation on the detection capability and the collection capability of traffic monitoring are pointed out. Subsequently, to resolve this problem, a multistage distributed traffic monitoring method is proposed in which several agents are dynamically linked in a manager/agent‐type traffic monitoring environment. The present method is applied to the fault management and security monitoring of a real network and the effectiveness of the method is demonstrated. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(8): 9–19, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10108
Parameter estimation and bit error rate of optimum receiver in a class‐A impulsive radio noise environment
Authors: Kanemoto Hideki , Miyamoto Shinichi , Morinaga Norihiko
Published: March 2003

Since most of the noise generated by electronic equipment using high‐frequency devices has statistical properties that are quite different from Gaussian noise, the bit error rate of conventional receivers is greatly degraded in a man‐made noise environment, because they are designed with the presumption of Gaussian noise. One of the methods of providing a better bit error rate in such a noise environment is the use of an optimum receiver. This optimum receiver attains a high bit error rate by using maximum likelihood symbol detection based on the statistical properties of the noise, and the statistical properties of the noise must be known a priori for optimum reception. In this paper, we use the Middleton class‐A impulsive radio noise model as the statistical model of the noise and study the parameter estimation and bit error rate of an optimum receiver in a class‐A impulsive radio noise environment. First, we evaluate the effect of errors in parameter estimation on the bit error rate of the optimum receiver in a class‐A impulsive radio noise environment, and show that to improve the performance of the optimum receiver in this noise environment, we should use parameters that express the statistics of the noise. Next we study the relationship between the number of noise samples used in estimation and the parameter estimation accuracy, and demonstrate that large numbers of noise samples are needed for highly accurate parameter estimation. However, it is shown that a quite good bit error rate can be obtained by the optimum receiver in the noise environment even if parameter estimation is based on a somewhat smaller number of noise samples (for example, about 700 samples for an impulsive indexA= 0.05 and a Gaussian component ratio Γ′ = 0.05). © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(8): 68–78, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1173
Volatility forecasting for risk management
Authors: Brooks Chris , Persand Gita
Published: March 2003

Recent research has suggested that forecast evaluation on the basis of standard statistical loss functions could prefer models which are sub‐optimal when used in a practical setting. This paper explores a number of statistical models for predicting the daily volatility of several key UK financial time series. The out‐of‐sample forecasting performance of various linear and GARCH‐type models of volatility are compared with forecasts derived from a multivariate approach. The forecasts are evaluated using traditional metrics, such as mean squared error, and also by how adequately they perform in a modern risk management setting. We find that the relative accuracies of the various methods are highly sensitive to the measure used to evaluate them. Such results have implications for any econometric time series forecasts which are subsequently employed in financial decision making. Copyright © 2002 John Wiley & Sons, Ltd.
Market risk management of banks: implications from the accuracy of Value‐at‐Risk forecasts
Authors: Wong Michael Chak Sham , Cheng Wai Yan , Wong Clement Yuk Pang
Published: March 2003

This paper adopts the backtesting criteria of the Basle Committee to compare the performance of a number of simple Value‐at‐Risk (VaR) models. These criteria provide a new standard on forecasting accuracy. Currently central banks in major money centres, under the auspices of the Basle Committee of the Bank of International settlement, adopt the VaR system to evaluate the market risk of their supervised banks. Banks are required to report VaRs to bank regulators with their internal models. These models must comply with Basle's backtesting criteria. If a bank fails the VaR backtesting, higher capital requirements will be imposed. VaR is a function of volatility forecasts. Past studies mostly conclude that ARCH and GARCH models provide better volatility forecasts. However, this paper finds that ARCH‐ and GARCH‐based VaR models consistently fail to meet Basle's backtesting criteria. These findings suggest that the use of ARCH‐ and GARCH‐based models to forecast their VaRs is not a reliable way to manage a bank's market risk. Copyright © 2002 John Wiley & Sons, Ltd.
Haematological, hepatic and renal alterations after repeated oral and intraperitoneal administration of monoisoamyl DMSA. II. Changes in female rats
Authors: Flora Swaran J. S. , Mehta Ashish
Published: March 2003

We recently reported the effects of repeated administration of the monoisoamyl ester of dimercaptosuccinic acid (MiADMSA) on a few selected biochemical variables indicative of haematopoietic, liver, kidney and brain toxicity, oxidative stress and essential metal status in male rats. The present investigation studies similar changes in female rats to ﬁnd out if the changes are independent of gender. The results suggest signiﬁcant and pronounced toxic effects of MiADMSA on haem biosynthesis, liver and kidneys in female rats exposed to higher doses of orally (p.o.) or intraperitoneally (i.p.) administered MiADMSA, compared with the effects in male rats. No effects on brain tissues were seen. A pronounced depletion of copper was noted in the blood and liver of MiADMSA administered rats, irrespective of route of exposure. It can be concluded that the administration of MiADMSA in female rats is confounded with side‐effects and may require caution during its use and further exploration. Copyright © 2003 John Wiley & Sons, Ltd.
Kupffer cells are responsible for liver cirrhosis induced by carbon tetrachloride
Authors: Muriel Pablo , Escobar Yesenia
Published: March 2003

Inhibition of Kupffer cells could disrupt the sequence of events leading to organ injury by damping down the ﬁbrogenic stimulus. To elucidate the role of Kupffer cells in liver ﬁbrosis and cirrhosis, rats were treated with gadolinium chloride (GdCl3) and cirrhosis was induced by subchronic carbon tetrachoride (CCl4) administration. Carbon tetrachloride was administered three times per week for 8 weeks to male Wistar rats treated simultaneously with GdCl3 (20 mg kg−1, i.p. daily); appropriate controls were performed. Serum enzyme activities of alkaline phosphatase (ALP), γ‐glutamyl transpeptidase (γ‐GTP) and alanine aminotransferase (ALT) and bilirubin concentration increased signiﬁcantly by CCl4, whereas GdCl3 prevented completely the increase in γ‐GTP and partially prevented the increase in ALP, ALT and bilirubins (P < 0.05). Liver glycogen was depleted by CCl4, an effect that GdCl3 was not capable of preventing. Moreover, gadolinium by itself depleted it. Lipid peroxidation increased about 2.5‐fold by administration with CCl4, whereas GdCl3 preserved lipid peroxidation within normal values. Hepatic collagen increased threefold after subchronic intoxication with CCl4 (P < 0.05) whereas GdCl3 prevented partially (P < 0.05) the increase in collagen content, as evidenced by the liver hydroxyproline content and by the histopathological analysis. The present results suggest that Kupffer cells are needed for the production of CCl4‐induced cirrhosis, because their inactivation with GdCl3 prevents the disease. Published in 2003 by John Wiley & Sons, Ltd.
Involvement of oxidative sress in the toxicity of 4‐monochlorophenol in Hep G2 cells in culture
Authors: Trufﬁn D. , Garçon G. , Hannothiaux M. H. , Colein P. , Shirali P. , Grave‐Descampiaux B.
Published: March 2003

Chlorophenols, mainly used as biocides, are compounds with a wide spectrum of toxic effects, including teratogenic and carcinogenic actions. The aim of this study was to examine possible 4‐monochlorophenol (4‐MCP) toxicity related to metabolic pathways, which may implicate semiquinones and reactive oxygen species (ROS), in human Hep G2 cells. The effects of 4‐MCP were performed through cytotoxicity assays (viability, ATP level), metabolic activities (4‐MCP intracellular concentration, NADPH cytochrome P‐450 reductase (Cyt P‐450 red.) and glutathione‐S‐transferase activities, CYP 3A7 mRNA expression) and oxidative stress (superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities, glutathione status, malondialdehyde concentration, CYP 2E1 mRNA expression). According to the literature, in this work Hep G2 cells were incubated in the continuous presence of 4‐MCP at 350 μM over 24 or 48 h. Results showed statistically signiﬁcant decreases in ATP levels (24 or 48 h, P < 0.05) versus controls. The 4‐MCP intracellular concentrations increased as early as 8–24 h and then decreased (P < 0.01). Decreases in Cyt. P‐450 red. (24 h, P < 0.05), catalase (24 h, P < 0.05; 48 h, P < 0.01), glutathione peroxidase activities (48 h, P < 0.05) and reduced glutathione concentrations (48 h, P < 0.05) were observed. In addition, exposure to 4‐MCP increased mRNA expressions of CYP 3A7 (24 h, P < 0.05; 48 h, P < 0.01) and CYP 2E1 (24 h, P < 0.01) versus controls. Taken together, these results suggest that 4‐MCP metabolites could induce oxidative stress conditions in Hep G2 cells. Published in 2003 by John Wiley & Sons, Ltd.
The adrenal cortex and steroidogenesis as cellular and molecular targets for toxicity: critical omissions from regulatory endocrine disrupter screening strategies for human health?
Authors: Harvey Philip W. , Everett David J.
Published: March 2003

Current testing strategies to assess the endocrine disrupting properties of chemicals have omitted examination of the adrenal gland and do not adequately cover the process of steroidogenesis. Steroidogenesis is critical for adrenocortical function as well as that of the testes and ovaries, and presents multiple molecular targets for toxicity, ranging from general effects on all steroidogenic tissues (e.g. via StAR protein or CYP11A1 cholesterol side‐chain cleavage) through to speciﬁc targets affecting only adrenocortical function (e.g. CYP11β/18 and glucocorticoid synthesis). Numerous chemicals of environmental relevance are now being shown to affect adrenocortical function both in vivo in aquatic species and in vitro in human cell lines, and given the vital role of the adrenal gland to human health and development, there is a strong case for including dedicated assessment techniques in screening batteries for endocrine‐disrupting chemicals, not least to assist in general data interpretation (e.g. whether adrenal hypertrophy is due to stress or to a more sinister adrenocortical insufﬁciency). Cell lines such as H295R (derived from a human adrenocortical adenocarcinoma) currently exist that will allow assessment of cortisol production and most of the major enzymes and functional proteins in the steroidogenic pathway (e.g. StAR; CYP11A1/scc; CYP11β/18; CYP17; CYP19; CYP21; 3β‐hydroxysteroid dehydrogenase). Adequate assessment of adrenocortical function, as with any component of the integrated endocrine system, probably also will require the development of speciﬁc in vivo methodology to include effects on hypothalamo‐pituitary function. Finally, although there is currently no direct evidence that environmental exposure to endocrine‐disrupting (oestrogenic) chemicals has actually caused adverse human health effects, lessons have been learned on their potential from the diethylstilboestrol case. Similar evidence exists from aminoglutethimide and etomidate on the lethal impact of unpredicted chemically induced adrenal insufﬁciency in sensitive human subgroups, and it would seem prudent to incorporate relevant tests for adrenal function and steroidogenesis into current regulatory validation programmes. Published in 2003 by John Wiley & Sons, Ltd.
Underarm cosmetics and breast cancer
Authors: Darbre P. D.
Published: March 2003

Although risk factors are known to include the loss of function of the susceptibility genes BRCA1/BRCA2 and lifetime exposure to oestrogen, the main causative agents in breast cancer remain unaccounted for. It has been suggested recently that underarm cosmetics might be a cause of breast cancer, because these cosmetics contain a variety of chemicals that are applied frequently to an area directly adjacent to the breast. The strongest supporting evidence comes from unexplained clinical observations showing a disproportionately high incidence of breast cancer in the upper outer quadrant of the breast, just the local area to which these cosmetics are applied. A biological basis for breast carcinogenesis could result from the ability of the various constituent chemicals to bind to DNA and to promote growth of the damaged cells. Multidisciplinary research is now needed to study the effect of long‐term use of the constituent chemicals of underarm cosmetics, because if there proves to be any link between these cosmetics and breast cancer then there might be options for the prevention of breast cancer. Copyright © 2003 John Wiley & Sons, Ltd.
Pesticide residue on/in the washed skin and its potential contribution to dermal toxicity
Authors: Zendzian Robert P.
Published: March 2003

Washing the skin of humans or experimental animals after exposure to a pesticide or other chemical may leave a major portion of the dose on/in the washed skin. Questions have been raised as to whether this skin residue can contribute to the toxicity of a pesticide by continued post‐wash absorption. In a set of 19 pesticides tested in the rat to determine the fate of this skin residue, absorption from the washed skin continued in 15 at all doses tested, continued in 2 pesticides at only some of the doses tested and did not continue in 2 volatile pesticides. However, only nine pesticides showed an increase in systemic concentration following absorption from the washed skin, which can be considered indicative of potential increased toxicity. The time of occurrence and magnitude of the increase varied with chemical and dose, being a combination of rate and magnitude of absorption and rate and magnitude of excretion of the absorbed chemical. Similar patterns of continued absorption of skin residue may be expected to occur in humans. Published in 2003 by John Wiley & Sons, Ltd.
Modeling an electrochemical process to remove Cr(VI) from rinse‐water in a stirred reactor
Authors: Rodríguez Miriam G , Aguilar Ricardo , Soto Gabriel , Martínez Sergio A
Published: March 2003

Experimental studies were developed in a batch reactor (16 dm3), to obtain the kinetic model of Cr(VI) removal by means of an electrochemical process. An overall kinetic model was obtained and experimentally validated in a continuous stirred electrochemical reactor (16 dm3) with synthetic and industrial wastewater. To develop the mathematical model of the continuous reactor in relation to the Cr(VI) and Fe(II) concentration in the solution, a classical mass balance procedure was performed. The Cr(VI) concentration in the electrochemically‐treated waters was less than 0.5 mg dm−3. In the electrochemical process the Cr(VI) reduction is caused by the Fe(II) released from the anode due to the electric current applied, by the Fe(II) released for the dissolution (corrosion) of the electrodes due to the acidic media, and by reduction at the cathode. During the process, reduction from Fe(III) to Fe(II) occurs. All of these different reactions cause a diminution in the quantity of sludge generated. Finally, it was found that due to the slow rate of reduction of Cr(VI) during the first part of the process it is necessary to develop a method of control to apply the process in a continuous industrial system.

© 2003 Society of Chemical Industry
Control of filamentous organisms in food‐processing wastewater treatment by intermittent aeration and selectors
Authors: Nakhla George , Lugowski Andrew
Published: March 2003

Various measures were tested at a full‐scale wastewater treatment plant to control sludge bulking by type 0041 and 0675 filamentous microorganisms, instigated by highly variable wastewater loadings from a food‐processing facility. Intermittent aeration on a 1‐h on 1‐h off basis was found to effect a marginal improvement in sludge settling characteristics, as reflected by about an 11–36% reduction in the Sludge Volume Index (SVI) to 118 cm−3 g−1. At BOD loadings of 1500 kg d−1 which marginally exceeded the design capacity of the plant of 1200 kg d−1, SVI rose sharply to 230 cm−3 g−1 in less than a week. The anoxic selector effected a reduction in SVI to 170 cm−3 g−1 within 3 weeks of operation at temperatures of 8–12 °C. The aerobic selector was most effective, reducing SVIs further to 79 cm−3 g−1 in 2 weeks. Sludge settleablity was found to be inversely proportional to the aerobic selector food‐to‐microorganism ratio. The optimum aerobic selector loading was found to be 1.8–2.7 kgBOD5 kgMLVSS d−1, with corresponding SVIs in the range of 80–120 cm−3 g−1.

© 2003 Society of Chemical Industry
Nitrite accumulation characteristics of high strength ammonia wastewater in an autotrophic nitrifying biofilm reactor
Authors: Yun Ho‐Joon , Kim Dong‐Jin
Published: March 2003

Selective nitrification was carried out to accumulate nitrite from high strength ammonia wastewater in an autotrophic nitrifying biofilm reactor. Nitrification efficiencies and nitrite accumulation characteristics were investigated at various operating conditions such as ammonium load, oxygen supply and free ammonia concentration. The biofilm reactor showed very stable nitrification efficiencies of more than 90% at up to 2 kg NH4‐N m−3 d−1 and the nitrite content was maintained at around 95%. Inhibition by free ammonia on nitrite oxidizers seems to be the major factor for nitrite accumulation. Batch kinetic analyses of ammonium and nitrite oxidation showed that nitrite oxidation activity was selectively inhibited in the presence of free ammonia. However, the activity recovered quickly as the free ammonia concentration decreased below the threshold inhibition concentration. Examination of specific ammonia and nitrite oxidation activities and the most probable number indicated that the number of nitrite‐oxidizing microorganisms in the nitrite‐accumulating system was less than that in the normal nitrification system due to long‐term free ammonia inhibition of the nitrite oxidizers. The reduced population of nitrite oxidizers in the biofilm system was also responsible for the accumulation of nitrite in the biofilm reactor.

© 2003 Society of Chemical Industry
Elimination of inorganic mercury from waste waters using crandallite‐type compounds
Authors: Monteagudo José M , Durán Antonio , Carmona Manuel S , Schwab Roland G , Higueras Pablo
Published: March 2003

The removal of inorganic mercury from waste water streams arising from mines, using an artificial amorphous compound of the crandallite type synthesized in our laboratory, Ca0.5Sr0.5Al3(OH)6(HPO4) (PO4), has been investigated. This compound exhibits an extremely wide range of ionic substitutions: Ca2+ and Sr2+ were interchanged with Hg2+, so the mercury content of the waste water, ranging from 70 to 90 ppm, was reduced to less than 0.1 ppm. The process has been studied under batch conditions. The crandallite showed a high capacity for the exchange of mercury from mercuric nitrate solutions, 1.555 meq g−1. The ion‐exchange equilibrium isotherms for Hg2+ were correlated by the Langmuir equation. The recovery of mercury from Hg‐crandallite using HCl solutions and thermal treatment was also studied. Optimum recuperation of mercury is achieved by chemical reaction with HCl solution (pH 2.25). At these conditions, 75% of the mercury is recovered as the HgCl42− complex in a simple batch process, and the crandallite (in the protonic form) can be reused.

© 2003 Society of Chemical Industry
Preparation and characterization of precipitated zinc silicates
Authors: Michalska Iwona , Krysztafkiewicz Andrzej , Bogacki Mariusz B , Jesionowski Teofil
Published: March 2003

The study aimed to obtain highly dispersed particles of zinc silicate, a potential filler of polymers or a paint pigment, by precipitation from solutions of sodium metasilicate and of zinc salts. The technique of silicate precipitation was worked out, and the conditions causing precipitation were optimized. The temperature, sodium metasilicate solution flow rate and concentration of zinc salts were selected so as to obtain silicates of the lowest possible bulk density, and which had low water‐absorbing capacity and high paraffin oil‐absorbing capacity. In the study, the effects of precipitation parameters were examined on the principal physicochemical properties of the silicates, the structure and uniform character of silicate particles, particle size distribution, and the surface morphology. Particular attention was devoted to the particle size distribution and the tendency to form primary agglomerates (aggregates) and secondary agglomerates, using dynamic light scattering (DLS). Studies were undertaken to develop a technique which could prevent formation of silicate particle agglomerates. With this aim, the silicates' surface was modified either during their precipitation or by the so‐called dry technique. For the modification, silane coupling agents were applied. The extent of silicate surface hydrophobicity was examined by estimation of the enthalpies of immersion of the modified silicate surface. The silicates obtained were tested as fillers of rubber mixtures (in butadiene–styrene rubber).

© 2003 Society of Chemical Industry
Bioremediation of toluene‐contaminated air using an external loop airlift bioreactor
Authors: Harding Rochelle C , Hill Gordon A , Lin Yen‐Han
Published: March 2003

An external loop airlift bioreactor (ELAB) has been used to capture and degrade toluene from a contaminated air stream. Using a spinning sparger, the toluene could be transferred from small, uniform bubbles into the aqueous culture media with an overall mass transfer coefficient as high as 1.1 h−1. Due to the very volatile nature of toluene, Pseudomonas putida (ATCC 23973) was cultured and maintained on benzyl alcohol, the first intermediate compound in the metabolic degradation pathway for toluene. Consequently, before successful continuous operation of the ELAB with toluene‐contaminated air, Pseudomonas putida was acclimatized to toluene by using 30 min intermittent sparging of contaminated air into the bioreactor. Continuous sparging of toluene‐contaminated air could then be successfully carried out with 100% capture and biodegradation efficiency at a contaminated air concentration of 15 mg dm−3 and a loading rate of 35 mg dm−3 h−1. Higher concentrations and loading rates were only partially degraded. Although this capture matches only the low rates reported earlier using biofilters to remediate toluene, the ELAB operates using submerged culture and requires no packing which can plug during biofilter operation. In this study, Pseudomonas putida grew on toluene at a maximum specific growth rate of only 0.05 h−1.

© 2003 Society of Chemical Industry
Identification and modelling of aerobic hydrolysis – application of optimal experimental design
Authors: Insel Güçlü , Orhon Derin , Vanrolleghem Peter A
Published: March 2003

Hydrolysis mechanism plays a dominant role in the delicate balance of electron donor/electron acceptor ratios in BNR and EBPR systems as an important carbon source. In this study, the surface‐saturation‐type hydrolysis kinetics was investigated based on respirometric measurements, within the context of the theoretical and the practical identifiability of mathematical models. The identifiable parameters of a selected model were derived from respirograms. In addition, the information from the experiments was evaluated on the basis of Optimal Experimental Design (OED) methodology for different initial conditions of the batch respirometric experiment.

© 2003 Society of Chemical Industry
Sustained nitrite accumulation in a membrane‐assisted bioreactor (MBR) for the treatment of ammonium‐rich wastewater
Authors: Wyffels Stijn , Boeckx Pascal , Pynaert Kris , Verstraete Willy , Van Cleemput Oswald
Published: March 2003

A membrane‐assisted bioreactor (MBR) for sustained nitrite accumulation is presented, treating a synthetic wastewater with total ammonium nitrogen (TAN) concentrations of 1 kg N m−3 at a hydraulic retention time down to 1 day. Complete biomass retention was obtained by microfiltration with submerged hollow fibre membranes. A membrane flux up to 189.5 dm3 day−1 m−2 could be maintained at a suction pressure below 100 kPa. Nitrification was effectively blocked at the nitrite stage (nitritation), and nitrate concentration was less than 29 g N m−3. The rate of aeration was reduced to obtain a mixture of ammonium and nitrite, and after adjusting this rate the TAN/NO2‐N ratio in the reactor effluent was kept around unity, making it suitable for further treatment by anaerobic oxidation of ammonium with nitrite. After increasing again the rate of aeration, complete nitrification to nitrate recovered after 11 days. It is suggested that nitrite accumulation resulted from a combination of factors. First, the dissolved oxygen (DO) concentration in the reactor was always limited with concentrations below 0.1 g DO m−3, thereby limiting nitrification and preventing significant nitrate formation. The latter is attributed to the fact that ammonium‐oxidising bacteria cope better with low DO concentrations than nitrite oxidisers. Second, the MBR was operated at a high ammonia concentration of 7–54 g N m−3, resulting in ammonia inhibition of the nitrite‐oxidising microorganisms. Third, a temperature of 35 °C was reported to yield a higher maximum growth rate for ammonium‐oxidising bacteria than for nitrite‐oxidising bacteria. Nitrite oxidisers were always present in the MBR but were out‐competed under the indicated process conditions, which is reflected in low concentrations of nitrate. Oxygen limitation was shown to be the most important factor to sustain nitrite accumulation. Nevertheless, nitritation was possible at ambient temperature (22–24 °C), lower ammonia concentration (<7 g N m−3) and when using raw nitrogenous wastewater containing some biodegradable carbon. Overall, application of the MBR for nitritation was shown to be a reliable technology.

© 2003 Society of Chemical Industry
Mass transfer and hydrodynamic characteristics in a co‐current downflow contacting column
Authors: Dursun G , Orhan R , Akosman C
Published: March 2003

Hydrodynamic and mass transfer characteristics of water–air system in a co‐current downflow contacting column (CDCC) were studied for various nozzle diameters at different superficial gas velocities and liquid re‐circulation rates. Gas hold‐up and liquid‐side mass transfer coefficient increased with increasing superficial gas velocity and liquid flow rate but decreased with increasing nozzle diameter. It is shown that correlations developed, which are based on liquid kinetic power per liquid volume present in the column, and superficial gas velocity explains gas hold‐up and the mass transfer coefficient within an error 20% for all gas and liquid flow rates and nozzle diameters used. The constants of correlations for gas hold‐up and mass transfer coefficient were found to be considerably different from other gas–liquid contacting systems.

© 2003 Society of Chemical Industry
Design and operation of unbaffled aerated agitated vessels with unsteadily forward–reverse rotating impellers handling viscous Newtonian liquids
Authors: Yoshida Masanori , Taguchi Yoji , Yamagiwa Kazuaki , Ohkawa Akira , Abe Masahiko , Tezura Shuichi , Shimazaki Masuo
Published: March 2003

Design and operation of unbaffled aerated agitated vessels with multiple unsteadily forward–reverse rotating impellers (AJITERs) for viscous Newtonian liquids were studied. The effects of operating conditions such as gas sparging rate, agitation rate and the number of impeller stages, geometrical conditions such as the diameters of vessel and impeller, and the physical properties of liquids on the drag and added moment of inertia coefficients, necessary to predict the average and maximum power consumptions of the impellers in AJITERs, were evaluated and the empirical relationships which estimate values of each of these coefficients are presented. The effects of operating conditions, geometrical conditions and liquid physical properties on the gas hold‐up, ϕgD, and volumetric oxygen transfer coefficient, kLaD, were evaluated in relation to the total power input which is the sum of the average power consumption of impellers, ie average agitation power input, and aeration power input. Empirical relationships, useful for design and operation of AJITERs, were obtained for each viscosity range, where the dependences of ϕgD and kLaD on the specific total power input and superficial gas velocity differed, to predict ϕgD and kLaD respectively as a function of the specific total power input, superficial gas velocity and liquid physical properties.

© 2003 Society of Chemical Industry
Gene transfer into the liver by plasmid injection into the portal vein combined with electroporation
Authors: Kobayashi Shogo , Dono Keizo , Tanaka Toshiyuki , Takahara Shiro , Isaka Yoshitaka , Imai Enyu , Nagano Hiroaki , Tomoaki Kato , Umeshita Koji , Nakamori Shoji , Sakon Masato , Monden Morito
Published: March 2003

Background

We investigated the optimum conditions for gene transfer into the liver by injection of plasmid via the portal vein combined with electroporation.

Methods

In anesthetized 7‐week‐old male Shionogi Wistar rats, a tapered 3Fr. catheter was inserted through a branch of the colonic vein and its tip was secured into the portal vein. After clamping the vessels around the right and caudal lobes of the liver, FITC‐oligodeoxynucleotide (ODN), green fluorescence protein (GFP) plasmid, or pCAGGS‐luciferase was injected into the right and caudal lobes during electroporation using electric pulses applied to the caudal lobe only.

Results

Transfected cells were identified by FITC‐ODN and GFP fluorescence, and transfection efficacy was estimated by measurement of luciferase activity. FITC‐ODN and GFP were detected in the caudal lobes of the liver. FITC‐ODN was particularly present in hepatocytes surrounding the Glisson capsule and central veins, while GFP was detected in only hepatocytes surrounding the Glisson capsule. Luciferase activity in the liver was dependent on the plasmid concentration and voltage of the electric pulse, but independent of the volume of plasmid solution. Luciferase activity was limited in the right lobe, in which plasmid solution was injected but no electroporation was applied.

Conclusions

Our results showed local expression of the induced gene at the electroporation site, suggesting it is potentially useful for liver function support during recovery after extensive liver surgery and for the treatment of chronic and/or diffuse liver diseases. Copyright © 2002 John Wiley & Sons, Ltd.
Vectors based on reducible polycations facilitate intracellular release of nucleic acids
Authors: Read Martin L. , Bremner K. Helen , Oupický David , Green Nicola K. , Searle Peter F. , Seymour Leonard W.
Published: March 2003

Background

Inefficient intracellular delivery of nucleic acids limits the therapeutic usefulness of synthetic vectors such as poly(L‐lysine) (PLL)/DNA polyplexes. This article reports on the characterisation of a new type of synthetic vector based on a linear reducible polycation (RPC) that can be cleaved by the intracellular environment to facilitate release of nucleic acids.

Methods

RPCs of molecular weight (mwt) 45 and 187 kDa were prepared by oxidative polycondensation of the peptide Cys‐Lys10‐Cys and used to condense nucleic acids. The stability of RPC‐based polyplexes to reduction was determined using electrophoresis, dynamic light scattering and fluorescence techniques. Transfection activity was studied in several cancer cell lines (HeLa, LNCaP, PC‐3 and B16‐F10) using luciferase and green fluorescent protein (GFP) genes as reporter genes in the presence of chloroquine or the cationic lipid (N‐(1‐(2,3‐dioleoyloxy)propyl)‐N, N, N‐trimethylammonium chloride) (DOTAP). A CMV‐driven plasmid expressing the nitroreductase (ntr) gene was used to evaluate the therapeutic efficacy of RPC‐based delivery vectors.

Results

A 187‐fold higher level of gene expression indicated that intracellular delivery of DNA was more efficient using RPC/DOTAP compared with vectors based on non‐reducible PLL. Analysis by flow cytometry also showed enhanced delivery of the GFP gene by RPC/DOTAP in HeLa (51.5 ± 7.9%), LNCaP (55.2 ± 6.7%) and PC‐3 (66.1 ± 3.7%) cells. Transfection with the ntr gene and treatment with the prodrug CB1954 resulted in significant cell killing, achieving IC50 values similar to those previously attained with adenoviral vectors. Delivery of mRNA (20–75% of cells) was also more efficient using RPC/DOTAP than PLL/DOTAP (<5% of cells).

Conclusions

These results demonstrate that lipid‐mediated activation of RPC‐based polyplexes is a useful strategy to enhance intracellular delivery of nucleic acids and potentiate therapeutic activity. Copyright © 2002 John Wiley & Sons, Ltd.
Massive apoptotic cell death in chemically induced rat urinary bladder carcinomas following in situ HSVtk electrogene transfer
Authors: Shibata Masa‐Aki , Horiguchi Taisuke , Morimoto Junji , Otsuki Yoshinori
Published: March 2003

Background

Gene delivery in current gene therapy studies relies largely on recombinant viral vectors. However, the safety of this method is still under investigation. The effectiveness of in vivo electrogene transfer as a means of gene therapy for rat bladder cancers using the herpes simplex virus 1 thymidine kinase (HSVtk) gene in combination with ganciclovir (GCV) was therefore investigated.

Methods

The killing effects of HSVtk/GCV therapy were evaluated in transitional cell carcinoma (TCC) cells in vitro and in vivo. In animal experiments, electrogene transfer of HSVtk into N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN)‐induced rat bladder tumors was conducted followed by GCV administration.

Results

In vitro studies demonstrated that approximately 50–70% of the TCC cells died as a result of transfection with pHSVtk and GCV administration and that this treatment was associated with decreased DNA synthesis and elevated activities of caspase‐3, ‐8 and ‐9. A significantly decreased mitochondrial membrane potential was also noted in TCC cells given pHSV tk + GCV. A direct single injection of HSVtk into bladder tumors using in vivo electrogene transfer followed by GCV i.p. administration resulted in significant increases in the levels of apoptosis and histopathological necrosis accompanied by marked inflammation. Active caspase‐3 was strongly expressed in the cell death areas of the TCC in rats given pHSVtk/GCV therapy.

Conclusions

In vivo electrogene transfer results in efficient gene transfer in BBN‐induced rat bladder tumors and the HSVtk/GCV prodrug system induces significant cell death which appears to be, at least, mediated via the mitochondrial apoptotic pathway. Copyright © 2002 John Wiley & Sons, Ltd.
Inhibition of HIV‐1 replication in primary human T cells transduced with an intracellular anti‐HIV‐1 p17 antibody gene
Authors: Tewari Deepanker , Notkins Abner Louis , Zhou Paul
Published: March 2003

Background

Previously we reported that human CD4+ T cell lines stably expressing anti‐HIV‐1 gag p17 scFv/Cκ in the cytosol or nucleus were resistant to HIV‐1 challenge. Inhibition of HIV‐1 by anti‐HIV‐1 gag p17 scFv/Cκ occurred at both the pre‐ and post‐integration steps of the viral cycle. To simulate more closely the in vivo infection process, in this study we tested anti‐HIV‐1 activity of anti‐HIV‐1 gag p17 scFv/Cκ in primary human T cells.

Methods

Anti‐HIV‐1 gag p17 scFv/Cκ gene that is targeted into cytoplasm was inserted into a MMLV vector and transfected into packaging cell line PT67. The recombinant virus was used to transduce primary human T cells and human CD4+ T cell line Jurkat. Following transduction, transduction efficiency, transgene expression, and cell phenotypes were studied. Transduced cells were then challenged with 100 TCID50 of HIV‐1 IIIB and primary isolate 5AO12. Following challenge, HIV‐1 replication was monitored by p24 production.

Results

Both transduced Jurkat and primary human T cells expressed the transgene. The expression of the transgene did not alter cell growth and CD4 or CD8 expression. However, HIV‐1 replication in scFv/Cκ‐transduced Jurkat cells was inhibited by nearly 90% as compared with vector controls. More importantly, HIV‐1 replication in primary human T cells from multiple donors transduced with the anti‐HIV‐1 gag p17 scFv/Cκ gene was inhibited by as much as 99% as compared with primary T cells transduced with the vector control. The inhibition of replication was not due to interference in viral entry or reverse transcription. The less that HIV‐1 replicated in different donor cells, the higher the degree of protection.

Conclusions

The expression of the anti‐HIV‐1 gag p17 scFv/Cκ gene construct in primary human T cells renders these cells resistant to HIV‐1 and points to the potential clinical usefulness of this gene construct for anti‐HIV‐1 gene therapy. Copyright © 2002 John Wiley & Sons, Ltd.
In vivo expansion of transduced murine hematopoietic cells with a selective amplifier gene
Authors: Kume Akihiro , Koremoto Masahide , Xu Ruifang , Okada Takashi , Mizukami Hiroaki , Hanazono Yutaka , Hasegawa Mamoru , Ozawa Keiya
Published: March 2003

Background

Hematopoietic stem‐cell‐directed gene transfer has achieved limited success in transducing clinically relevant levels of target cells. The expansion of gene‐modified cells is one way to circumvent the problem of inefficient transduction with current vectors. To this end, we have developed ‘selective amplifier genes’ (SAGs) that encode chimeric proteins that are a fusion of granulocyte colony‐stimulating factor receptor and the steroid‐binding domain. Prototype SAGs conferred estrogen‐responsive growth on murine hematopoietic progenitors.

Methods

We constructed a retroviral vector coexpressing an SAG for 4‐hydroxytamoxifen (Tm)‐specific proliferation and the enhanced green fluorescent protein (EGFP). Murine bone marrow cells were transduced with this vector and transplanted into myeloablated mice. Subsequently, recipients were challenged with Tm, and EGFP+ cells were enumerated.

Results

The challenge induced a significant increase in EGFP+ leukocytes (21 ± 4% to 27 ± 5%), while EGFP+ cells decreased in untreated animals (21 ± 5% to 10 ± 3%). Three months later, bone marrow cells were transplanted from the unchallenged mice to secondary hosts. Again the administration of Tm resulted in an increase of EGFP+ cells (16 ± 4% to 35 ± 3%), contrasting to a decrease in controls (22 ± 4% to 12 ± 4%), and the difference was significant for more than 3 months. A detailed study of lineage showed a preferential expansion of EGFP+ cells in granulocytes and monocytes following Tm administration.

Conclusions

Long‐term repopulating cells were transduced with the SAG, and the transduced granulocyte/monocyte precursors were most likely to be expandable in vivo upon Tm stimulation. Copyright © 2002 John Wiley & Sons, Ltd.