bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of calcium on Manduca sexta plasmatocyte spreading and network formation
Authors: Willott Elizabeth , Hallberg Constance A. , Tran Hung Q. 
Published: August 2002

AbstractPlasmatocytes are a class of insect hemocytes important in the cellular defense response. In some species, they are phagocytic, protecting the insect from smaller pathogens. In many insects, they work in concert with other hemocytes (particularly other plasmatocytes and granular cells) to form nodules and to encapsulate foreign material. To perform these functions, plasmatocytes attach to, spread on, and surround suitable targets. Because of their importance, because we had previously observed that prolonged incubation of hemocytes in solutions containing the divalent cation chelator ethylenediaminetetraacetic acid (EDTA) inhibited plasmatocyte spreading, and because of the importance of divalent cations in many immune‐related functions, we investigated the effect of calcium and magnesium on spreading of plasmatocytes from fifth instar Manduca sexta larvae. On glass slides, plasmatocytes spread more quickly and elongated in Grace’s medium containing 5 mM calcium, compared to calcium‐free medium. In the presence of calcium, plasmatocyte adhesion, spreading, and network formation were not visibly different in magnesium‐free and magnesium‐containing Grace’s medium. Using immunomicroscopy with a monoclonal antibody specific for plasmatocytes, we measured the length and width of plasmatocytes incubated with several different concentrations of calcium. Plasmatocyte length positively correlated with calcium concentration to 5 mM (maximum concentration tested and approximately the hemolymph concentration). Mean plasmatocyte width was less in 0 and 5 mM calcium than in 0.05 or 0.5 mM calcium. On plastic, hemocytes survived longer than on glass (they survived beyond 24 h) and, in 5 mM calcium, formed an extensive network readily visible by phase‐contrast microscopy. This network was never as extensive in the absence of calcium. Network formation in the absence of magnesium, but presence of calcium, resembled network formation in standard Grace’s medium. Arch. Insect Biochem. Physiol. 49:187–202, 2002. © 2002 Wiley‐Liss, Inc.
Cholinergic regulation of the corpora allata in adult male loreyi leafworm Mythimna loreyi
Authors: Kou Rong 
Published: August 2002

AbstractThe direct effect of acetylcholine on the activation of the corpora allata (CA) was investigated in the adult male loreyi leafworm, Mythimna loreyi. Acetylcholine, in the presence of the choline esterase inhibitor physostigmine (50 μM), elicited a stimulatory effect on juvenile hormone acids (JHAs) release from the CA. Maximum effect was obtained at concentrations of 10 and 50 μM. Repeated administration of 10 μM acetylcholine on the same CA did not elicit similar stimulatory effect. Since JHA release can be significantly activated by carbachol and not by nicotine, this cholinergic effect is likely to belong to the muscarinic type. The effect of acetylcholine was significantly antagonized by gallamine triethiodide (M2 antagonist) and 4‐DAMP (M3 antagonist), pirenzepine (M1 antagonist), and tropicamide (M4 antagonist) were ineffective. It is concluded that in the adult male M. loreyi, the cholinergic regulation of CA is most likely via M2 and M3 muscarinic receptors.Arch. Insect Biochem. Physiol. 49:215–224, 2002. © 2002 Wiley‐Liss, Inc.
Seasonal changes in glycerol content and enzyme activities in overwintering larvae of the Shonai ecotype of the rice stem borer, Chilo suppressalis Walker
Authors: Li Yi‐Ping , Ding Lei , Goto Michiyo 
Published: August 2002

AbstractEnzymes associated with glycogen metabolism and glycerol synthesis in larvae of the Shonai ecotype of the rice stem borer, Chilo suppressalis, were investigated over the winter in 2000–2001. Glycerol content was scarcely detected in September and October, rapidly increased in November and December, peaked in January, and then decreased. Glycogen was converted to glycerol over the winter until February, and glycerol was reconverted to glycogen in March. The trehalose content remained constant over the winter. The activities of enzymes associated with glycerol synthesis changed with the season. Glycerol accumulation was accomplished by activation of glycogen phosphorylase, inhibition of fructose‐1,6‐bisphosphatase and pyruvate kinase, and activation of enzymes associated with glycerol synthesis, mainly glyceraldehyde‐3‐ phosphatase and polyol dehydrogenase with glyceraldehyde activity. These changes led to a diversion of triose phosphates into the pathway of glycerol synthesis. However, activities of the two initial enzymes of the hexose monophosphate shunt were not activated and remained relatively constant, but high during the period of active glycerol synthesis. Both decreasing temperature in the field and the transition from the diapause to the post‐diapause state may be responsible for the changes in activities of enzymes associated with glycerol synthesis. Arch. Insect Biochem. Physiol. 50:53–61, 2002. © 2002 Wiley‐Liss, Inc.
Leucine transport in membrane vesicles from Chironomus riparius larvae displays a mélange of crown‐group features
Authors: Parenti Paolo , Forcella Matilde , Pugliese Anna , Giacchini Roberto , Rossaro Bruno , Hanozet Giorgio M. 
Published: August 2002

AbstractLeucine uptake into membrane vesicles from larvae of the midge Chironomus riparius was studied. The membrane preparation was highly enriched in typical brush border membrane enzymes and depleted of other membrane contaminants. In the absence of cations, there was a stereospecific uptake of l‐leucine, which exhibited saturation kinetics. Parameters were determined both at neutral (Km 33 ± 5 μM and Vmax 22.6 ± 6.8 pmol/7s/mg protein) and alkaline (Km 46 ± 5 μM and Vmax 15.5 ± 2.5 pmol/7s/mg protein) pH values. At alkaline pH, external sodium increased the affinity for leucine (Km 17 ± 1 μM) and the maximal uptake rate (Vmax 74.0 ± 12.5 pmol/7s/mg protein). Stimulation of leucine uptake by external alkaline pH agreed with lumen pH measurements in vivo. Competition experiments indicated that at alkaline pH, the transport system readily accepts most L‐amino acids, including branched, unbranched, and α‐methylated amino acids, histidine and lysine, but has a low affinity for phenylalanine, β‐amino acids, and N‐methylated amino acids. At neutral pH, the transport has a decreased affinity for lysine, glycine, and α‐methylleucine. Taken together, these data are consistent with the presence in midges of two distinct leucine transport systems, which combine characters of the lepidopteran amino acid transport system and of the sodium‐dependent system from lower neopterans. Arch. Insect Biochem. Physiol. 48:51–62, 2001. © 2001 Wiley‐Liss, Inc.
Form and function: The impact of query term and operator usage on Web search results
Authors: Lucas Wendy , Topi Heikki 
Published: August 2002

AbstractConventional wisdom holds that queries to information retrieval systems will yield more relevant results if they contain multiple topic‐related terms and use Boolean and phrase operators to enhance interpretation. Although studies have shown that the users of Web‐based search engines typically enter short, term‐based queries and rarely use search operators, little information exists concerning the effects of term and operator usage on the relevancy of search results. In this study, search engine users formulated queries on eight search topics. Each query was submitted to the user‐specified search engine, and relevancy ratings for the retrieved pages were assigned. Expert‐formulated queries were also submitted and provided a basis for comparing relevancy ratings across search engines. Data analysis based on our research model of the term and operator factors affecting relevancy was then conducted. The results show that the difference in the number of terms between expert and nonexpert searches, the percentage of matching terms between those searches, and the erroneous use of nonsupported operators in nonexpert searches explain most of the variation in the relevancy of search results. These findings highlight the need for designing search engine interfaces that provide greater support in the areas of term selection and operator usage.
A context vector model for information retrieval
Authors: Billhardt Holger , Borrajo Daniel , Maojo Victor 
Published: August 2002

AbstractIn the vector space model for information retrieval, term vectors are pair‐wise orthogonal, that is, terms are assumed to be independent. It is well known that this assumption is too restrictive. In this article, we present our work on an indexing and retrieval method that, based on the vector space model, incorporates term dependencies and thus obtains semantically richer representations of documents. First, we generate term context vectors based on the co‐occurrence of terms in the same documents. These vectors are used to calculate context vectors for documents. We present different techniques for estimating the dependencies among terms. We also define term weights that can be employed in the model. Experimental results on four text collections (MED, CRANFIELD, CISI, and CACM) show that the incorporation of term dependencies in the retrieval process performs statistically significantly better than the classical vector space model with IDF weights. We also show that the degree of semantic matching versus direct word matching that performs best varies on the four collections. We conclude that the model performs well for certain types of queries and, generally, for information tasks with high recall requirements. Therefore, we propose the use of the context vector model in combination with other, direct word‐matching methods.
Effect of intermittent and continuous exposure to electromagnetic fields on cultured hippocampal cells
Authors: Boland A. , Delapierre D. , Mossay D. , Dresse A. , Seutin V. 
Published: August 2002

AbstractThis study was designed to assess the effect of 50 Hz electromagnetic fields (EMFs) on hippocampal cell cultures in the presence or absence of either sodium nitroprusside (SNP, a NO donor) or Fe2+ induced oxidative stress. One week old cultured rat hippocampal cells were exposed to either intermittent EMFs (IEMFs, 50 Hz, 0–5 mT, 1 min ON/OFF cycles, repeated 10 times every 2 h, 6 times/day during 48 h) or continuous EMFs (CEMFs, 50 Hz, 0–5 mT for 48 h). In a second set of experiments, the effect on such EMFs applied in combination with oxidative stress induced by 0.5 μM Fe2+ or SNP was estimated. At the end of both sets of experiments, cell mortality was assessed by lactate dehydrogenase measurements (LDH). Neither type of exposure to EMFs was observed to modify the basal rate of cell mortality. The exposure to CEMFs in presence of either NO or Fe2+ did not induce any significant increase in cell death. However, when cells were exposed to EMFs in the presence of NO, we observed a significant increase in cell death of 11 and 23% (P<0.001) at 2.5 and 5 mT, respectively. This effect had some specificity because IEMFs did not modify the effect of Fe2+ on cell mortality. Although the effects of IEMFs reported in this study were only observed at very high intensities, our model may prove valuable in trying to identify one cellular target of EMFs. Bioelectromagnetics 23:97–105, 2002. © 2002 Wiley‐Liss, Inc.
Missing link in firefly bioluminescence revealed: NO regulation of photocyte respiration
Authors: Greenfield Michael D. 
Published: August 2002

AbstractSexual communication in most species of fireflies is a male–female dialogue of precisely timed flashes of bioluminescent light. The biochemical reactions underlying firefly bioluminescence have been known for 30 years and are now exploited in biomedical assays and other commercial applications. Several aspects of flash regulation are also understood: flash rhythm is controlled by a central pattern generator, and individual flashes are neurally triggered, with octopamine serving as the transmitter. The molecular oxygen needed by the biochemical reactants is delivered by a network of tracheal arborizations extending throughout the light organ (lantern). However, the actual means by which oxygen quickly reaches the reactants packaged within specialized photocytes and the specific event(s) triggered by neural action have not been identified; termination of axons away from the photocytes has exacerbated the latter problem. A recent paper(1) by a consortium of cell and evolutionary biologists, however, reports that nitric oxide (NO), manufactured and released in response to neuronal discharge, is the missing link by which neural action in the firefly lantern yields a sudden flash of light. BioEssays 23:992–995, 2001. © 2001 John Wiley & Sons, Inc.
Effects of parent training on parent and child behavior using procedures based on functional analyses
Authors: Marcus Bethany A. , Swanson Victoria , Vollmer Timothy R. 
Published: August 2002

AbstractWe evaluated the effects of parent training for four children whose aberrant behaviors were maintained by social positive or negative reinforcement. Interventions were based on the behavioral function of the problem behavior. Child participants were four children (ages 3 to 5 years) who had developmental delays and exhibited significant aberrant behaviors (tantrums and aggression). The children's mothers were the parent participants. The children's behavior improved as a function of the parents' performance. Copyright © 2001 John Wiley & Sons, Ltd.
Teaching social‐learning procedures to paraprofessionals working with individuals with severe mental illness in a maximum‐security forensic hospital
Authors: Jones Nicole T. , Menditto Anthony A. , Geeson Lynn R. , Larson Elaine , Sadewhite Lisa 
Published: August 2002

AbstractThis study describes an integrated technical method for teaching learning‐based interventions to paraprofessionals working in a maximum‐security psychiatric facility as a social‐learning program was implemented. This training approach combines brief didactic instruction with live demonstration and guided practice in specific procedures. Comparisons between baseline and post‐training functioning of staff were made using ongoing direct observational assessment data. Results revealed that following training and program implementation staff were much more active overall, interacted with clients far more often, and engaged in much lower rates of job‐irrelevant activity. Moreover, following training direct observational data of the patterns of staff–client interactions showed that staff were much more likely to demonstrate interactions reflective of learning‐based interventions than at baseline. These results have important implications for clinicians and administrators attempting to implement behavioral rehabilitation programs. Copyright © 2001 John Wiley & Sons, Ltd.
Upper electron‐excited states in bioluminescence: experimental indication
Authors: Kudryasheva N. S. , Nemtseva E. V. , Meshalkin Yu. P. , Sizykh A. G. 
Published: August 2002

AbstractThe involvement of upper electron‐excited states in bacterial bioluminescence process was studied with excitation energy‐accepting molecules. The fluorescent aromatic compounds, anthracene and 1.4‐bis(5‐phenyloxazol‐2‐yl)benzene, were chosen. Energies of their lowest excited singlet states are higher than the energy of the analogous state of the bioluminescence emitter; their absorption spectra and bioluminescence do not overlap. Hence, the excitation of these molecules by singlet–singlet energy transfer or by light absorption is excluded. Sensitized fluorescence of these compounds in the bioluminescence systems has been recorded, indicating the activity of upper electron‐excited states in the bioluminescent process. Copyright © 2001 John Wiley & Sons, Ltd.
An optimized solid phase synthesis strategy— including on‐resin lactamization—of astressin, its retro‐, inverso‐, and retro–inverso isomers as corticotropin releasing factor antagonists
Authors: Rijkers Dirk T. S. , den Hartog Jack A. J. , Liskamp Rob M. J. 
Published: August 2002

AbstractThis report describes an optimized solid phase synthesis strategy for astressin and new derivatives thereof. The synthesis is based on 9‐fluorenylmethyloxycarbonyl/allyl/tert‐butyl chemistry. The glutamic acid and lysine residue, which together form the cyclic constraint by coupling of their side chains, were protected by allyl functionalities during the synthesis of the linear peptide. Allyl removal by Pd(0) and the construction of the lactam bridge have been performed on‐resin after completion of the chain assembly. This synthetic methodology resulted in high chemical yields (58–72%) and excellent purities of the crude peptides. The peptides were tested for their binding at the corticotropin releasing factor receptor, type 1, and their corticotropin releasing factor antagonistic activity. Furthermore, astressin and its analogs were studied by CD in order to determine the secondary structure in solution. Since the linear form of astressin and also the cyclic inverso isomer were found to be fully inactive, it can be concluded that a cyclic constraint and a right‐handed α‐helix, respectively, are of utmost importance for these peptides to act as corticotropin releasing factor antagonists. © 2002 John Wiley & Sons, Inc. Biopolymers 63: 141–149, 2002
Photomodulation of conformational states. III. Water‐soluble bis‐cysteinyl‐peptides with (4‐aminomethyl) phenylazobenzoic acid as backbone constituent*
Authors: Renner Christian , Behrendt Raymond , Heim Nicola , Moroder Luis 
Published: August 2002

AbstractIn previous studies we have shown that light‐induced cis/trans isomerization of the azobenzene moiety in cyclo‐[Ala–Cys–Ala–Thr–Cys–Asp–Gly–Phe–AMPB] [AMPB: (4‐aminomethyl)phenylazobenzoic acid] leads both in the monocyclic and in the oxidized bicyclic form to markedly differentiated conformational states in DMSO, a fact that lends itself for photomodulation of the redox potential of such bis‐cysteinyl‐peptides. For this purpose water‐soluble systems are required, and this was achieved by replacing three residues outside the Cys–Ala–Thr–Cys active‐site motif of thioredoxin reductase with lysines. The resulting cyclo‐[Lys–Cys–Ala–Thr–Cys–Asp–Lys–Lys–AMPB] fully retains its photoresponsive properties in water as well assessed by uv and CD measurements. Paralleling results of the previously investigated azobenzene‐containing cyclic peptides, the trans → cis isomerization of the water‐soluble monocyclic and oxidized bicyclic peptide is accompanied by a marked transition from a well‐defined conformation to an ensemble of possible conformations. However, the conformational preferences are very dissimilar from those of the DMSO‐soluble peptides. In fact, hydrogen bonds as well as secondary structure elements were found that change in the mono‐ and bicyclic peptide upon irradiation. The photo switch between different turn types and hydrogen bonding networks offers the structural rational for the significantly differentiated redox potentials, but also the possibility of monitoring by femtosecond uv‐vis and ir spectroscopy fast and ultra fast backbone rearrangement processes following the electronic trans → cis isomerization. © 2002 Wiley Periodicals, Inc. Biopolymers 63: 382–393, 2002
Influence of netropsin's charges on the minor groove width of d(CGCGAATTCGCG)2
Authors: Wellenzohn Bernd , Flader Wolfgang , Winger Rudolf H. , Hallbrucker Andreas , Mayer Erwin , Liedl Klaus R. 
Published: August 2002

AbstractThe exact understanding of the interaction of minor groove binding drugs with DNA is of interest due to their importance as transcription controlling drugs. In this study we performed four molecular dynamics simulations, one of the uncomplexed d(CGCGAATTCGCG)2 dodecamer and three simulations of the DNA complexed with the minor groove binder netropsin. The charged guanidinium and amidinium ends of the small ligand were in one simulation formally uncharged, in the second one normally charged, and in the third simulation we doubled the charges of the two ends. So we are able to filter out the influence the charges exert on the DNA structure. The positive charges reduce the width of the minor groove showing that charges are able to modify the groove width by charge neutralization of the negative phosphate groups. The quality of the used force field was successfully tested by comparing the results of the uncomplexed dodecamer with already reported NMR and x‐ray studies. Thus our simulations should be able to describe the minor groove width of DNA in a correct manner underlying the validity of the results. © 2002 Wiley Periodicals, Inc. Biopolymers 61: 276–286, 2002
Contribution of secondary structure to the heat capacity and enthalpy distribution of the unfolded state in proteins
Authors: Poland Douglas 
Published: August 2002

AbstractWe have recently shown that one can construct the enthalpy distribution for protein molecules from experimental knowledge of the temperature dependence of the heat capacity. For many proteins the enthalpy distribution evaluated at the midpoint of the denaturation transition (corresponding to the maximum in the heat capacity vs temperature curve) is broad and biphasic, indicating two different populations of molecules (native and unfolded) with distinctly different enthalpies. At temperatures above the denaturation point, the heat capacity for the unfolded state in many proteins is quite large and using the analysis just mentioned, we obtain a gaussian‐like enthalpy distribution that is very broad. A large value of the heat capacity indicates that there are structural changes going on in the unfolded state above the transition temperature. In the present paper we investigate the origin of this large heat capacity by considering the presence of changing amounts of secondary structure (specifically, α‐helix) in the unfolded state. For this purpose we use the empirical estimates of the Zimm–Bragg σ and s factors for all of the native amino acids in water as determined by Scheraga and co‐workers. Using myoglobin as an example, we calculate probability profiles and distribution functions for the total number of helix states in the specific‐sequence molecule. Given the partition function for the specific‐sequence molecule, we can then calculate a set of enthalpy moments for the molecule from which we obtain a good estimate of the enthalpy distribution in the unfolded state. This distribution turns out to be quite narrow when compared with the distribution obtained from the raw heat capacity data. We conclude that there must be other major structural changes (backbone and solvent) that are not accounted for by the inclusion of α‐helix in the unfolded state. © 2002 John Wiley & Sons, Inc. Biopolymers 63: 59–65, 2002
Surface transformation of bioactive glass in bioreactors simulating microgravity conditions. Part II: Numerical simulations
Authors: Gao H. , Ayyaswamy P. S. , Ducheyne P. , Radin S. 
Published: August 2002

AbstractThe effects of simulated microgravity on the surface modification of bioactive glass (BG) in solution were studied using a numerical method. Models were developed for estimating the mass transfers of different chemical species from the surface of bioactive glass particles (microcarriers) suspended in the rotating liquid medium of a NASA‐designed high aspect ratio vessel (HARV) bioreactor and on the bottom surface of a static vial. The concentration profiles resulting from chemical reactions and ionic transports were ascertained. Numerical results for the transport under simulated microgravity in the HARV and at normal gravity in the static vial were compared. These results were also compared with those of experiments to verify the enhancement of the reaction kinetics under simulated microgravity conditions. The experimental and numerical studies confirm that simulated microgravity conditions lead to the quick achievement of bioactive glass surface modification. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 379–385, 2001.