bluuebunny/crossref_metadata_2025_split huggingface dataset:
Human exposure to 2450 MHz CW energy at levels outside the IEEE C95.1 standard does not increase core temperature†
Authors: Adair Eleanor R. , Mylacraine Kevin S. , Cobb Brenda L. 
Published: August 2002

AbstractPermission was received from the Brooks AFB Institutional Review Board and the AF Surgeon General's Office to exceed the peak power density (PD = 35 mW/cm2) we had previously studied during partial body exposure of human volunteers at 2450 MHz. Two additional peak PD were tested (50 and 70 mW/cm2). The higher of these PD (normalized peak local SAR = 15.4 W/kg) is well outside the IEEE C95.1 guidelines for partial body exposure, as is the estimated whole body SAR ≈ 1.0 W/kg. Seven volunteers (four males, three females) were tested at each PD in three ambient temperatures (Ta = 24, 28, and 31°C) under our standard protocol (30 min baseline, 45 min RF exposure, 10 min baseline). The thermophysiological data (esophageal and six skin temperatures, metabolic heat production, local sweat rate, and local skin blood flow) were combined with comparable data at PD = 0, 27, and 35 mW/cm2 from our 1999 study to generate response functions across PD. No change in esophageal temperature or metabolic heat production was recorded at any PD in any Ta. At PD = 70 mW/cm2, skin temperature on the upper back (irradiated directly) increased 4.0°C in Ta = 24°C, 2.6°C in Ta = 28°C, and 1.8°C in Ta = 31°C. These differences were primarily due to the increase in local sweat rate, which was greatest in Ta = 31°C. Also at PD = 70 mW/cm2, local skin blood flow on the back increased 65% over baseline levels in Ta = 31°C, but only 40% in Ta = 24°C. Although Ta becomes an important variable when RF exposure exceeds the C95.1 partial body exposure limits, vigorous heat loss responses of blood flow and sweating maintain thermal homeostasis efficiently. It is also clear that strong sensations of heat and thermal discomfort will motivate a timely retreat from a strong RF field, long before these physiological responses are exhausted. Bioelectromagnetics 22:429–439, 2001. Published 2001 Wiley‐Liss, Inc.
Empirical validation of SAR values predicted by FDTD modeling*†
Authors: Gajsek P. , Walters T.J. , Hurt W.D. , Ziriax J.M. , Nelson D.A. , Mason P.A. 
Published: August 2002

AbstractRapid increase in the use of numerical techniques to predict current density or specific absorption rate (SAR) in sophisticated three dimensional anatomical computer models of man and animals has resulted in the need to understand how numerical solutions of the complex electrodynamics equations match with empirical measurements. This aspect is particularly important because different numerical codes and computer models are used in research settings as a guide in designing clinical devices, telecommunication systems, and safety standards. To ensure compliance with safety guidelines during equipment design, manufacturing and maintenance, realistic and accurate models could be used as a bridge between empirical data and actual exposure conditions. Before these tools are transitioned into the hands of health safety officers and system designers, their accuracy and limitations must be verified under a variety of exposure conditions using available analytical and empirical dosimetry techniques. In this paper, empirical validation of SAR values predicted by finite difference time domain (FDTD) numerical code on sphere and rat is presented. The results of this study show a good agreement between empirical and theoretical methods and, thus, offer a relatively high confidence in SAR predictions obtained from digital anatomical models based on the FDTD numerical code. Bioelectromagnetics 23:37–48, 2002. © 2002 Wiley‐Liss, Inc.
Derangement of growth and differentiation control in oncogenesis
Authors: Corn Paul G. , El‐Deiry Wafik S. 
Published: August 2002

AbstractHuman neoplasms develop following the progressive accumulation of genetic and epigenetic alterations to oncogenes and tumor suppressor genes. These alterations confer a growth advantage to the cancer cell, leading to its clonal proliferation, invasion into surrounding tissues, and spread to distant organs. Genes that are altered in neoplasia affect three major biologic pathways that normally regulate cell growth and tissue homeostasis: the cell cycle, apoptosis, and differentiation. While each of these pathways can be defined by a unique set of molecular events, they are not biologically separate. Rather, they function more as an integrated molecular network, and perturbations in one pathway can have profound consequences on another. Insights into what distinguishes the regulation of growth and differentiation in a normal cell versus a cancer cell have led to the development of novel anticancer therapies. BioEssays 24:83–90, 2002. © 2002 John Wiley & Sons, Inc.
Embryonic origin of the eyes in teleost fish
Authors: Chuang Jui Chang , Raymond Pamela A. 
Published: August 2002

AbstractThe developmental history of the vertebrate eye begins at an early embryonic stage, with the formation of the body axes and induction of neural tissue. Several recent experimental embryological and genetic studies in teleost fish have produced new insights into the morphogenetic and molecular regulation of eye formation. Molecular signaling pathways and patterned expression of transcription factors implicated in eye determination are discussed, and the importance of morphogenetic cell movements is emphasized. BioEssays 24:519–529, 2002. © 2002 Wiley Periodicals, Inc.
An analysis of the selective effects of NCR with punishment targeting problem behavior associated with positive affect
Authors: Rush Karena S. , Crockett Jennifer L. , Hagopian Louis P. 
Published: August 2002

AbstractAmong individuals with developmental disabilities and behavioral problems, self‐injury and aggression are often associated with negative affect such as crying. In the current report, we present data on two children who displayed problem behaviors (screaming and self‐injury) that were often associated with positive affect. In contrast to their other problem behaviors that were socially mediated, these behaviors were maintained independent of social consequences. One concern about treating problem behavior associated with positive affect is that the treatment may produce generalized reductions in positive affect. In both cases presented in the current study, the reductive effects of a treatment targeting these behaviors were highly selective, producing decreases in screaming and self‐injury, while minimally affecting affect. Copyright © 2001 John Wiley & Sons, Ltd.
Fluorescence quenching properties and chemiluminescence responses of α‐ketothiols derivatized with o‐phthalaldehyde and primary amino compounds
Authors: Sano Akira , Nakamura Hiroshi 
Published: August 2002

AbstractFluorescence and chemiluminescence responses of thiols derivatized with o‐phthalaldehyde (OPA) and primary amines have been studied. Among thiols tested, those having an α‐ketothiol structure [R‐CH(SH)‐CO‐] were found to give extremely low fluorescence intensities when derivatized with OPA and L‐valine. The relative fluorescence intensities of α‐ketothiols, such as mercaptoacetic acid (MAA), 2‐mercaptopropionic acid (2‐MPA), mercaptosuccinic acid (MSA) and N‐(2‐mercaptopropionyl)glycine (MPG), were only below 3% of that of N‐acetyl‐L‐cysteine (NAC), having no α‐ketothiol structure. The addition of detergents such as sodium dodecylsulphate had no effect on the fluorescence and an aprotic solvent (dimethylsulphoxide) showed little effect, whereas these thiols chemiluminesced intensely when derivatized with OPA and N‐(4‐aminobutyl)‐N‐ethylisoluminol as a primary amine and successively detected by high‐performance liquid chromatography (HPLC) with postcolumn chemiluminescence reactions using hydrogen peroxide and haematin. The relative chemiluminescence intensities of MSA, 2‐MPA and MPG to NAC were 41.0%, 27.8% and 117%, respectively. MPG was estimated to be detectable at a concentration level of at least 10 fmol per injection. In conclusion, the weak fluorescence of the α‐ketothiols derivatized with OPA and primary amines is probably due to the low fluorescence quantum yields of the derivatives, and HPLC with a chemiluminescence detection system is useful for the sensitive detection of thiols. Copyright © 2001 John Wiley & Sons, Ltd.
Kinetics studies of ultraweak luminescence induced by ascorbic acid in Characeae cells and their structures
Authors: Jaśkowska A. , Borc R. , Milczarek I. , Dudziak A. , Śpiewla E. 
Published: August 2002

AbstractNative non‐stressed Nitellopsis obtusa cells emit low‐intensity (10–104 photons s−1 cm−2) electromagnetic radiation within the visible range. The intensity of emission by these cells is several times higher than the intensity of the environmental medium. This luminescence appears as a long‐lived (observable not for hours but for a few days) spontaneous light emission, sensitized by chlorophyll. Cells exposed to ascorbic acid action emit ultraweak radiation, dependent on reagent concentrations. Ultraweak luminescence (UL) intensity increases with rise in concentration, reaching maximum for higher concentrations faster and also changing the kinetics of UL decay. Studies of UL kinetics for different substructures and fractions, as well as for intact cells, allow us to consider single‐ and double‐exponential functions as decay curves, which could suggest two ways of ascorbic acid action in the cells. In the spectral distribution, the bands of chlorophyll, dimoles of singlet oxygen and NADH, FMN and Q10, which are electron carriers of the respiration chain, can be taken into consideration. Ascorbic acid action shows an increase in the red part of spectrum, except 627 nm, and in these bands of emission, which can be associated with the electron carriers of the respiration chain and lipid peroxidation. Copyright © 2001 John Wiley & Sons, Ltd.
Properties of firefly luciferase immobilized through a biotin carboxyl carrier protein domain
Authors: Eu Jiyang , Andrade Joseph 
Published: August 2002

AbstractA fusion protein, consisting of biotin carboxyl carrier protein (BCCP) domain from Escherichia coli and firefly luciferase (FL) from Photinus pyralis, was immobilized through the biotin–avidin interaction on 6% cross‐linked agarose beads. Several properties of the immobilized BCCP–FL were studied. Immobilized and free enzymes showed no significant difference in thermal stability; both retained at least 91% activity after incubation at 4°C and 25°C for 22 h. Incubation at 37°C for 22 h caused significant activity loss. KM and kcat values were determined for both free and immobilized enzymes. KM values were similar between free and immobilized enzymes; however, kcat of immobilized BCCP–FL was one‐third of the kcat of the free enzyme. 294 µmol/L Co‐enzyme A (CoA) and 44 mmol/L dithiothreitol (DTT) enhanced the total bioluminescence output. Triton X‐100, Tween 20, PEG 8,000, PVP 40,000 and PVP 360,000 did not enhance the bioluminescence reaction of immobilized BCCP–FL. Copyright © 2001 John Wiley & Sons, Ltd.
Homonuclear 1H‐NMR assignment and structural characterization of human immunodeficiency virus type 1 Tat Mal protein
Authors: Grégoire Catherine , Péloponèse Jean‐Marie , Esquieu Didier , Opi Sandrine , Campbell Grant , Solomiac Murielle , Lebrun Evelyne , Lebreton Jacques , Loret Erwann P. 
Published: August 2002

AbstractThe transacting transcriptional activator (Tat) is a viral protein essential for activation of the human immunodeficiency virus (HIV) genes, and it plays an important role in HIV induced immunodeficiency. We report the NMR structural characterization of the active Tat Mal variant that belongs to a highly virulent D‐subtype HIV type‐1 (HIV‐1) strain (Mal) found mainly in Africa. A full Tat Mal protein (87 residues) is synthesized. This synthetic protein is active in a transactivation assay with HeLa cells infected with the HIV long terminal repeated noncoding sequences of the HIV‐1 provirus (LTR) lac Z gene. Homonuclear 1H‐NMR spectra allows the sequential assignment of the Tat Mal spin systems. Simulating annealing generates 20 conformers with similar folding. The geometry of the mean structure is optimized with energy minimization to obtain a final structure. As the European variant (Tat Bru) the N‐terminal region of Tat Mal constitutes the core, and there is a hydrophobic pocket composed of the conserved Trp 11 interacting with several aromatic residues. The two functional regions of Tat (basic and the cysteine‐rich regions) are well exposed to the solvent. A short α‐helix is observed in region V adjacent to the basic region. This α helix induces local structural variations compared to the NMR structure of Tat Bru, and it brings the cysteine‐rich and basic regions closer. This study suggests that similar folding exists among Tat variants. © 2001 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 324–335, 2001
In vitro adaptation of a ligase ribozyme for activity under a low‐pH condition
Authors: Miyamoto Yoshitaka , Teramoto Naozumi , Imanishi Yukio , Ito Yoshihiro 
Published: August 2002

AbstractA ligase ribozyme accelerating a ligation reaction with oligonucleotide under a low‐pH condition was selected by in vitro adaptation. A ribozyme active at pH 7 was randomly mutated, and the resultant RNA library was subjected to in vitro adaptation under a low‐pH reaction condition. At pH 4, the adapted RNAs reacted with the oligonucleotide substrates about 200 times faster than the original ribozyme. When the ribozyme was cloned and sequenced, 10 of the 30 clones sequenced had identical sequences. The differences in sequence from the original ribozyme were found at four positions in the middle region and at the 3′ end. A few sequential differences dominated the activity of the ribozyme under the extreme condition. The adapted ribozyme had one repeating sequence that was critical for the activity. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 590–596, 2001.
Acetate‐inducible protein overexpression from the glnAp2 promoter of Escherichia coli
Authors: Farmer William R. , Liao James C. 
Published: August 2002

AbstractThe Ntr regulon in Escherichia coli has previously been engineered to control the expression of a heterologous metabolic pathway. In this study, we reengineered the same system for protein production. In the absence of NRII (glnL gene product), we showed that glnAp2 can be an effective promoter for protein production that is inducible by exogenous acetate, but both the induction ratio and the range of modulation are low. To deal with this issue, we inactivated phosphotransacetylase (pta gene product), which disrupts the acetate pathway and denies the cell the ability to synthesize acetate. With this additional modification, gene expression from glnAp2 can be controlled by directly adding acetate into the growth medium. Using a lacZ reporter fusion, we found that glnAp2 induction was modulatable over a range of potassium acetate concentrations, and the induction/noninduction ratio increased to 77 in the absence of pta. The extracellular acetate required for maximal induction is lower than the concentration that causes toxicity, and thus growth inhibition by acetate addition was not a matter of concern. Furthermore, compared to the Ptac promoter, overexpression of a model protein using the modified glnAp2 promoter system did not cause significant growth inhibition, although a higher level of protein expression was achieved. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 504–509, 2001.
Automatic inducer addition and harvesting of recombinant Escherichia coli cultures based on indirect on‐line estimation of biomass concentration and specific growth rate
Authors: Eriksen Niels Thomas , Kratchmarova Irina , Neve Søren , Kristiansen Karsten , Iversen Jens Jørgen Lønsmann 
Published: August 2002

AbstractThis article describes a novel bioreactor configuration for production optimization of recombinant proteins in Escherichia coli. Inducer addition and harvesting are controlled on‐line based on indirect estimation of biomass concentration and specific growth rate from addition of NaOH to maintain constant pH. When either a predetermined biomass concentration is reached or the cultures have obtained, a constant specific growth rate inducer is introduced automatically. The induction period is ended by automatic harvesting of the cultures either at a predetermined biomass concentration or when substrate (in this study glucose) is depleted, detected as an increase of pH, or dissolved oxygen tension. During harvesting, metabolic activities are quenched within 3 min by cooling of the cell suspension. The system has been used to optimize expression of glutathione S‐transferase (GST) fusion protein of the ligand binding domain of mouse peroxisome proliferator‐activated receptor, GST‐PPARα LBD. Total yield of GST‐PPARα LBD was independent of the time of inducer addition as long as the length of induction period corresponded to at least 0.25 cell divisions while the yield of soluble GST‐PPARα LBD, the only active form, increased with the length of induction period. Highest yields were obtained when the inducer was added at low cell concentration as soon as constant specific growth rate was detected, resulting in induction periods corresponding to 3.4 ± 0.4 cell divisions. The specific growth rate remained almost constant for one cell division after inducer addition, whereafter it decreased. No decrease of specific growth rate was observed when inducer was added in the lag‐phase, and no soluble protein was produced. These results suggest that solely soluble GST‐PPARα LBD acts as a growth inhibitor and that GST‐PPARα LBD is expressed predominantly as inclusion bodies immediately after inducer addition whereas the proportion expressed as soluble protein is increased after 1 h of induction. Compared to the procedures, which are generally used for protein expression in the laboratory, this system is less labor intensive, it automatically provides recording of biomass concentration and specific growth rate, and it allows direct comparisons between expression of different proteins and performance of different constructs since the induction period is linked to growth. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 355–361, 2001.
Toluene bioconversion to p‐hydroxybenzoate by fed‐batch cultures of recombinant Pseudomonas putida
Authors: Miller Edward S. , Peretti Steven W. 
Published: August 2002

AbstractA microbial oxidation process for the production of p‐hydroxybenzoate (HBA) from toluene is reported. The oxidation reaction was studied in fed‐batch fermentations using a recombinant Pseudomonas putida grown on glutamate as the sole carbon and energy source with salicylate and IPTG induction of tmoABCDE, and pchCF and phbz pathway genes, respectively. An average volumetric HBA productivity of 13.4 mg HBA L−1 h−1 was obtained under rapid growth conditions (glutamate excess), giving an HBA titer of 132 mg L−1 after 9.8 h of fermentation. This corresponded to an average specific HBA productivity of 7.2 μg HBA (mg total protein)−1 h−1. In contrast, maximum HBA titers of 35 mg HBA L−1 were achieved in 27 h in comparative studies employing glutumate limited fed‐batch cultures. A specific productivity of 4.1 μg HBA (mg total protein)−1 h−1 and volumetric productivity of 1.3 mg HBA L−1 h−1 were calculated for the growth‐rate restricted cultures. The differences in HBA production between the two cultures could be correlated to the levels of specific toluene‐4‐monooxygenase (T4MO) polypeptides. T4MO catalyzes the rate‐limiting step in the pathway. Using experimental data, the half‐life value of TmoA was calculated to be approximately 28 h. Assuming linear, monomolecular decay of TmoA, a specific degradation constant of 0.025 h−1 was calculated, which placed the stability of recombinant TmoA in the range of relatively stable proteins, even in the absence of co‐expression of tmoF, the terminal oxidoreductase subunit of T4MO. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 340–351, 2002.
Substrate‐permeable encapsulation of enzymes maintains effective activity, stabilizes against denaturation, and protects against proteolytic degradation
Authors: Nasseau Mathieu , Boublik Yvan , Meier Wolfgang , Winterhalter Mathias , Fournier Didier 
Published: August 2002

AbstractHow can enzymes be protected against denaturation and proteolysis while keeping them in a fully functional state? One solution is to encapsulate the enzymes into liposomes, which enhances their stability against denaturation and proteases. However, the permeability barrier of the lipid membrane drastically reduces the activity of enzyme entrapped in the liposome by reducing the internal concentration of the substrate. To overcome this problem, we permeabilized the wall of the liposome by reconstitution of a porin from Escherichia coli. In this way, we recovered the full functionality of the enzyme while retaining the protection against denaturation and proteolytic enzymes. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 615–618, 2001.
Calculation of effective diffusivities for biofilms and tissues
Authors: Wood Brian D. , Quintard Michel , Whitaker Stephen 
Published: August 2002

AbstractIn this study we describe a scheme for numerically calculating the effective diffusivity of cellular systems such as biofilms and tissues. This work extends previous studies in which we developed the macroscale representations of the transport equations for cellular systems based on the subcellular‐scale transport and reaction processes. A finite‐difference model is used to predict the effective diffusivity of a cellular system on the basis of the subcellular‐scale geometry and transport parameters. The effective diffusivity is predicted for a complex three‐dimensional structure that is based on laboratory observations of a biofilm, and these numerical predictions are compared with predictions from a simple analytical solution and with experimental data. Our results indicate that, under many practical circumstances, the simple analytical solution can be used to provide reasonable estimates of the effective diffusivity. © 2002 John Wiley &&num;38; Sons, Inc. Biotechnol Bioeng 77:495–516, 2002; DOI 10.1002/bit.10075
Decoupling cell growth and product formation in Chinese hamster ovary cells through metabolic control
Authors: Altamirano C. , Cairó J. J. , Gòdia F. 
Published: August 2002

AbstractThe development of a strategy for the culture of Chinese hamster ovary (CHO) cells producing tissue plasminogen activator (t‐PA) is investigated. This strategy is based on the replacement of the main carbon source, glucose, by another compound that is slowly metabolizable, particularly galactose. The introduction of this change allows for acute change in cell behavior at various levels. Cell growth is stopped after this nutrient shift, and the cells can be kept in long‐duration culture at a low growth rate and high viability as compared with a culture strategy based solely on glucose utilization. Moreover, the capability of cells to produce recombinant proteins (t‐PA in this work) can be maintained over the entire period of galactose feeding. From the metabolic point of view, use of a slowly metabolizable carbon source (galactose) introduces important changes in the production of lactate, ammonia, and some amino acids. The use of this metabolic shift enables the generation of biphasic processes, with a first phase with cell growth on glucose and a second stationary phase on galactose, which is particularly suited to perfusion systems. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 351–360, 2001.