bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unsaturated incompressible flows in adsorbing porous media
Authors: Fasano A. , Solonnikov V. 
Published: October 2003

AbstractWe study a free boundary problem modelling the penetration of a liquid through a porous material in the presence of absorbing granules. The geometry is one dimensional. The early stage of penetration is considered, when the flow is unsaturated. Since the hydraulic conductivity depends both on saturation and on porosity and the latter change due to the absorption, the main coefficient in the flow equation depends on the free boundary and on the history of the process. Some results have been obtained in Fasano (Math. Meth. Appl. Sci. 1999; 22:605) for a simplified version of the model. Here existence and uniqueness are proved in a class of weighted Hölder spaces in a more general situation. A basic tool are the estimates on a non‐standard linear boundary value problem for the heat equation in an initially degenerate domain (Rend. Mat. Acc. Lincei 2002; 13:23). Copyright © 2003 John Wiley & Sons, Ltd.
The solution of Lyumkis energy transport model in semiconductor science
Authors: Chen Li , Hsiao Ling 
Published: October 2003

AbstractThe existence and uniqueness of $ (W_{\hskip -3.5pt p}^{2,1}(Q_{\tau}))^{2}\times L_{q}(0,\tau;W_{\hskip -2.5pt q}^{1}(\Omega))$ solution to Lyumkis energy transport model is discussed for N+2<p≤q<∞ and 1≤N≤3. Copyright © 2003 John Wiley & Sons, Ltd.
Integration of [U‐13C]glucose and 2H2O for quantification of hepatic glucose production and gluconeogenesis
Authors: Perdigoto Rui , Rodrigues Tiago B. , Furtado Alexandre L. , Porto Armando , Geraldes Carlos F. G. C. , Jones John G. 
Published: October 2003

AbstractGlucose metabolism in five healthy subjects fasted for 16 h was measured with a combination of [U‐13C]glucose and 2H2O tracers. Phenylbutyric acid was also provided to sample hepatic glutamine for the presence of 13C‐isotopomers derived from the incorporation of [U‐13C]glucose products into the hepatic Krebs cycle. Glucose production (GP) was quantified by 13C NMR analysis of the monoacetone derivative of plasma glucose following a primed infusion of [U‐13C]glucose and provided reasonable estimates (1.90 ± 0.19 mg/kg/min with a range of 1.60–2.15 mg/kg/min). The same derivative yielded measurements of plasma glucose 2H‐enrichment from 2H2O by 2H NMR from which the contribution of glycogenolytic and gluconeogenic fluxes to GP was obtained (0.87 ± 0.14 and 1.03 ± 0.10 mg/kg/min, respectively). Hepatic glutamine 13C‐isotopomers representing multiply‐enriched oxaloacetate and [U‐13C]acetyl‐CoA were identified as multiplets in the 13C NMR signals of the glutamine moiety of urinary phenylacetylglutamine, demonstrating entry of the [U‐13C]glucose tracer into both oxidative and anaplerotic pathways of the hepatic Krebs cycle. These isotopomers contributed 0.1–0.2% excess enrichment to carbons 2 and 3 and ∼0.05% to carbon 4 of glutamine. Copyright © 2003 John Wiley & Sons, Ltd.
A new dimension of 1H‐NMR spectroscopy in assessment of liver graft dysfunction
Authors: Singh H. K. , Yachha S. K. , Saxena Rajan , Gupta Ashish , Nagana Gowda G. A. , Bhandari M. , Khetrapal C. L. 
Published: October 2003

AbstractHigh‐resolution 1H‐NMR spectroscopy of serum and urine samples of an 11‐year‐old male living related orthotopic liver transplant recipient is reported. Serum glutamine increased to abnormal levels along with simultaneous abnormal excretion of urinary glutamine post‐transplantation. High levels of glutamine in both blood and urine and concomitant reduced urea levels in urine were found to be evidence of impairment in urea cycle and compatible with persistently abnormal graft function. Thus glutamine levels in serum and urine, and urea in the urine as observed by 1H‐NMR spectroscopy highlight their important roles in monitoring liver graft function; increased glutamine levels lead to brain damage, if untreated. Copyright © 2003 John Wiley & Sons, Ltd.
Correlation between the occurrence of 1H‐MRS lipid signal, necrosis and lipid droplets during C6 rat glioma development
Authors: Zoula Sonja , Hérigault Gwénaël , Ziegler Anne , Farion Régine , Décorps Michel , Rémy Chantal 
Published: October 2003

AbstractThe aim of this study was to investigate the possible correlation between the 1H MRS mobile lipid signal, necrosis and lipid droplets in C6 rat glioma. First, the occurrence of necrosis and lipid droplets was determined during tumor development, by a histological analysis performed on 34 rats. Neither necrosis nor lipid droplets were observed before 18 days post‐implantation. At later stages of development, both necrosis and lipid droplets were apparent, the lipid droplets being mainly located within the necrotic areas. Using a second group of eight rats, a temporal correlation was evidenced between mobile lipid signal detected by in vivo single‐voxel one‐ (136 ms echo time) and two‐dimensional J‐resolved 1H MR spectroscopy, and the presence of necrosis and lipid droplets on the histological sections obtained from the brains of the same rats. Finally, spatial distribution of the mobile lipid signal was analyzed by chemical‐shift imaging performed on a third group of eight animals, at the end of the tumor growth. The spectroscopic image corresponding to the resonance of mobile lipids had its maximum intensity in the center of the tumor where necrotic regions were observed on the histological sections. These necrotic areas contained large amounts of lipid droplets. All these results suggest that mobile lipids detected in vivo by 1H MRS (136 ms echo time) in C6 rat brain glioma arise mainly from lipid droplets located in necrosis. Copyright © 2003 John Wiley & Sons, Ltd.
Biochemical characterization of muscle tissue of limb girdle muscular dystrophy: An 1H and 13C NMR study
Authors: Sharma Uma , Atri Surinder , Sharma M. C. , Sarkar Chitra , Jagannathan N. R. 
Published: October 2003

AbstractThe metabolic differences between the muscle biopsies of patients with limb girdle muscular dystrophy (LGMD) and normal controls were characterized using high‐resolution 1H and 13C NMR spectroscopy. In all, 44 metabolites were unambiguously assigned in the perchloric acid extracts of skeletal muscle tissue, using 2D double quantum filtered (DQF COSY), total correlation (TOCSY), and 1H/13C heteronuclear multiple quantum coherence (HMQC) spectroscopy. The concentrations of glycolytic substrate, glucose (p = 0.03), gluconeogenic amino acids, glutamine (p = 0.02) and alanine (p = 0.009) together with glycolytic product, lactate (p = 0.04), were found to be significantly lowered in LGMD patients as compared with controls. The reduction in the concentration of glucose may be attributed to the decrease in the concentration of gluconeogenic amino acids in the degenerated muscle. Reduction in the rate of anaerobic glycolysis and lowered substrate concentration appear to be the possible reasons for the decrease in the concentration of lactate. A significant reduction in the concentration of choline in LGMD patients was also observed compared with controls. Lower concentration of choline may be the result of decreased rate of membrane turnover in LGMD patients. The data presented here provide an insight into the potentials of in‐vitro NMR spectroscopy in the study of muscle metabolism. Copyright © 2003 John Wiley & Sons, Ltd.
Two‐dimensional NMR spectroscopy of urinary glycosaminoglycans from patients with different mucopolysaccharidoses
Authors: Hochuli Michel , Wüthrich Kurt , Steinmann Beat 
Published: October 2003

AbstractPatients with different types of mucopolysaccharidoses (MPS) lack specific lysosomal enzymes, which leads to tissue accumulation and urinary excretion of glycosaminoglycans (GAGs). Since little is known about the molecular composition of the excreted GAG fragments, we used two‐dimensional [1H,13C]‐correlation nuclear magnetic resonance (NMR) spectroscopy for a detailed analysis of the urinary GAGs of patients with MPS types I, II, IIIA, IVA and VI. The method revealed that the molecular structures of the excreted GAGs, i.e. heparan sulfate (HS), dermatan sulfate (DS), chondroitin sulfate (CS), and keratan sulfate (KS) are clearly distinct for the different MPS types. The chain terminal residues that are the normal substrates for the defective enzymes constitute characteristic sets of signals for each MPS type. The GAG chains show variations in carbohydrate composition and sulfation patterns that can be related to the different MPS types and clinical features. For example, two patients with MPS IIIA (M. Sanfilippo) with signs of CNS degeneration but only mild somatic features excrete a highly sulfated variant of HS, resembling HS in porcine brain, whereas a patient with MPS I (M. Scheie) and two patients with MPS II (M. Hunter), who present primarily with coarse facial features, joint contractures and skeletal deformities excrete a different type of HS with lower sulfation. In another case study, a patient with MPS IVA (M. Morquio), who presented mainly with skeletal dysplasia, excreted not only excessive amounts of KS but also a highly sulfated CS variant, resembling CS in articular cartilage. The high‐resolution NMR analysis of urinary GAGs presented here for the first time provides a solid basis for future studies with a larger number of patients to further explore pathogenesis and course of the MPS diseases. Copyright © 2003 John Wiley & Sons, Ltd.
Limits on volume changes in the mushroom bodies of the honey bee brain
Authors: Fahrbach Susan E. , Farris Sarah M. , Sullivan Joseph P. , Robinson G.E. 
Published: October 2003

AbstractThe behavioral maturation of adult worker honey bees is influenced by a rising titer of juvenile hormone (JH), and is temporally correlated with an increase in the volume of the neuropil of the mushroom bodies, a brain region involved in learning and memory. We explored the stability of this neuropil expansion and its possible dependence on JH. We studied the volume of the mushroom bodies in adult bees deprived of JH by surgical removal of the source glands, the corpora allata. We also asked if the neuropil expansion detected in foragers persists when bees no longer engage in foraging, either because of the onset of winter or because colony social structure was experimentally manipulated to cause some bees to revert from foraging to tending brood (nursing). Results show that adult exposure to JH is not necessary for growth of the mushroom body neuropil, and that the volume of the mushroom body neuropil in adult bees is not reduced if foraging stops. These results are interpreted in the context of a qualitative model that posits that mushroom body neuropil volume enlargement in the honey bee has both experience‐independent and experience‐dependent components. © 2003 Wiley Periodicals, Inc. J Neurobiol 57:141–151, 2003
Dehydroepiandrosterone upregulates neural androgen receptor level and transcriptional activity
Authors: Lu Shi‐Fang , Mo Qianxing , Hu Shan , Garippa Carrie , Simon Neal G. 
Published: October 2003

AbstractThe mechanism of action of dehydroepiandrosterone (DHEA), a neuroactive neurosteroid synthesized in the brains of humans and other mammals, has not been fully characterized in the adult brain. Although well known for modulatory effects on GABAA, NMDA, and σ1 receptors, studies in both CNS and peripheral target cells suggest that DHEA also may exert genomic effects via the androgen receptor (AR). The current study tested the hypothesis that DHEA was capable of producing androgenic effects in the CNS by assaying its ability to induce three characteristic effects of an androgenic compound. These included the ability to upregulate neural AR protein level in mouse brain and immortalized GT1–7 hypothalamic cells, the capacity to induce transcriptional activity through AR in CV‐1 cells transfected with an MMTV‐ARE‐CAT reporter, and competition for recombinant AR binding in a radioligand binding assay. The results showed that DHEA treatment significantly augmented AR both in vivo and in vitro, and that this effect was not blocked by trilostane (TRIL), a known 3β‐hydroxysteroid dehydrogenase (3β‐HSD) inhibitor. DHEA also promoted AR‐mediated CAT reporter expression and competed with dihydrotestosterone (DHT) for binding to recombinant AR in a cell‐free system. These data indicate that DHEA possesses intrinsic androgenic activity that is potentially independent of metabolic conversion to other androgens, and that it can affect gene function through the AR. In combination with its modulation of neurotransmitter receptors at the cell membrane level, the findings suggest that the mechanism of action of DHEA in the brain can involve a “crosstalk” cellular signaling system that involves both nongenomic and genomic components. © 2003 Wiley Periodicals, Inc. J Neurobiol 57: 163–171, 2003
Neural correlates to flight‐related density‐dependent phase characteristics in locusts
Authors: Fuchs E. , Kutsch W. , Ayali A. 
Published: October 2003

AbstractLocust phase polymorphism is an extreme example of behavioral plasticity; in response to changes in population density, locusts dramatically alter their behavior. These changes in behavior facilitate the appearance of various morphological and physiological phase characteristics. One of the principal behavioral changes is the more intense flight behavior and improved flight performance of gregarious locusts compared to solitary ones. Surprisingly, the neurophysiological basis of the behavioral phase characteristics has received little attention. Here we present density‐dependent differences in flight‐related sensory and central neural elements in the desert locust. Using techniques already established for gregarious locusts, we compared the response of locusts of both phases to controlled wind stimuli. Gregarious locusts demonstrated a lower threshold for wind‐induced flight initiation. Wind‐induced spiking activity in the locust tritocerebral commissure giants (TCG, a pair of identified interneurons that relay input from head hair receptors to thoracic motor centers) was found to be weaker in solitary locusts compared to gregarious ones. The solitary locusts' TCG also demonstrated much stronger spike frequency adaptation in response to wind stimuli. Although the number of forehead wind sensitive hairs was found to be larger in solitary locusts, the stimuli conveyed to their flight motor centers were weaker. The tritocerebral commissure dwarf (TCD) is an inhibitory flight‐related interneuron in the locust that responds to light stimuli. An increase in TCD spontaneous activity in dark conditions was significantly stronger in gregarious locusts than in solitary ones. Thus, phase‐dependent differences in the activity of flight‐related interneurons reflect behavioral phase characteristics. © 2003 Wiley Periodicals, Inc. J Neurobiol 57: 152–162, 2003
Specification of motoneuron fate in Drosophila: Integration of positive and negative transcription factor inputs by a minimal eve enhancer
Authors: McDonald Jocelyn A. , Fujioka Miki , Odden Joanne P. , Jaynes James B. , Doe Chris Q. 
Published: October 2003

AbstractWe are interested in the mechanisms that generate neuronal diversity within the Drosophila central nervous system (CNS), and in particular in the development of a single identified motoneuron called RP2. Expression of the homeodomain transcription factor Even‐skipped (Eve) is required for RP2 to establish proper connectivity with its muscle target. Here we investigate the mechanisms by which eve is specifically expressed within the RP2 motoneuron lineage. Within the NB4‐2 lineage, expression of eve first occurs in the precursor of RP2, called GMC4‐2a. We identify a small 500 base pair eve enhancer that mediates eve expression in GMC4‐2a. We show that four different transcription factors (Prospero, Huckebein, Fushi tarazu, and Pdm1) are all expressed in GMC4‐2a, and are required to activate eve via this minimal enhancer, and that one transcription factor (Klumpfuss) represses eve expression via this element. All four positively acting transcription factors act independently, regulating eve but not each other. Thus, the eve enhancer integrates multiple positive and negative transcription factor inputs to restrict eve expression to a single precursor cell (GMC4‐2a) and its RP2 motoneuron progeny. © 2003 Wiley Periodicals, Inc. J Neurobiol 57: 193–203, 2003
Balance of cell proliferation and death among dynamic populations: A mathematical model
Authors: Miller Michael W. 
Published: October 2003

AbstractDevelopmental changes in cell numbers represent the dynamic balance between cell proliferation and death. One obstacle to assessing this balance is an inability to quantify the total amount of cell death, i.e., with a positive indicator such as terminal dUTP nick end labeling (TUNEL) or caspase activity. A novel mathematical model is described wherein data on daily cell growth (the change in cell number) and cell cycle kinetics can be used to determine the total amount of cell death. Two sets of data from previously published studies were tested in this model; primary cultured cortical neurons and B104 neuroblastoma cells. These two preparations have contrasting features: neuronal cultures are heterogeneous and have relatively few cells that are actively cycling (i.e., the growth fraction for these cells is low), whereas B104 cells are relatively homogeneous cultures in which the growth fraction is high. In primary cortical cultures, there was a balance in cell production and death. Treatment with a potent anti‐mitogen, ethanol (400 mg/dl), affected this balance principally by reducing cell production, although the rate of cell death was also increased. In untreated B104 cells, there was eight‐fold more cell production than cell death. Growth factors such as platelet‐derived growth factor BB doubled cell production. Ethanol reduced cell production by >60%, and it eliminated growth factor‐mediated cell production. All of these changes occurred in the absence of an effect on the amount of cell death. Thus, the model is ideal for predicting the effects of an epigenetic factor (e.g., a growth factor, toxin, or pharmacological agent) on cell development and can be useful in determining the consequences of a genetic manipulation as well. © 2003 Wiley Periodicals, Inc. J Neurobiol 57:172–182, 2003
Rapid electrical and delayed molecular signals regulate the serum response element after nerve injury: Convergence of injury and learning signals
Authors: Lin Hana , Bao Jianxin , Ying Ju‐Sung , Walters Edgar T. , Ambron Richard T. 
Published: October 2003

AbstractAxotomy elicits changes in gene expression, but little is known about how information from the site of injury is communicated to the cell nucleus. We crushed nerves in Aplysia californica and the sciatic nerve in the mouse and found short‐ and long‐term activation of an Elk1‐SRF transcription complex that binds to the serum response element (SRE). The enhanced short‐term binding appeared rapidly and was attributed to the injury‐induced activation of an Elk1 kinase that phosphorylates Elk1 at ser383. This kinase is the previously described Aplysia (ap) ERK2 homologue, apMAPK. Nerve crush evoked action potentials that propagated along the axon to the cell soma. Exposing axons to medium containing high K+, which evoked a similar burst of spikes, or bathing the ganglia in 20 μM serotonin (5HT) for 20 min, activated the apMAPK and enhanced SRE binding. Since 5HT is released in response to electrical activity, our data indicate that the short‐term process is initiated by an injury‐induced electrical discharge that causes the release of 5HT which activates apMAPK. 5HT is also released in response to noxious stimuli for aversive learning. Hence, apMAPK is a point of convergence for injury signals and learning signals. The delay before the onset of the long‐term SRE binding was reduced when the crush was closer to the ganglion and was attributed to an Elk1 kinase that is activated by injury in the axon and retrogradely transported to the cell body. Although this Elk1 kinase phosphorylates mammalian rElk1 at ser383, it is distinct from apMAPK. © 2003 Wiley Periodicals, Inc. J Neurobiol 57: 204–220, 2003
Non‐reflecting artificial boundaries for transient scalar wave propagation in a two‐dimensional infinite homogeneous layer
Authors: Zhao Chongbin , Liu Tianyun 
Published: October 2003

AbstractThis paper presents an exact non‐reflecting boundary condition for dealing with transient scalar wave propagation problems in a two‐dimensional infinite homogeneous layer. In order to model the complicated geometry and material properties in the near field, two vertical artificial boundaries are considered in the infinite layer so as to truncate the infinite domain into a finite domain. This treatment requires the appropriate boundary conditions, which are often referred to as the artificial boundary conditions, to be applied on the truncated boundaries. Since the infinite extension direction is different for these two truncated vertical boundaries, namely one extends toward x →∞ and another extends toward x→‐ ∞, the non‐reflecting boundary condition needs to be derived on these two boundaries. Applying the variable separation method to the wave equation results in a reduction in spatial variables by one. The reduced wave equation, which is a time‐dependent partial differential equation with only one spatial variable, can be further changed into a linear first‐order ordinary differential equation by using both the operator splitting method and the modal radiation function concept simultaneously. As a result, the non‐reflecting artificial boundary condition can be obtained by solving the ordinary differential equation whose stability is ensured. Some numerical examples have demonstrated that the non‐reflecting boundary condition is of high accuracy in dealing with scalar wave propagation problems in infinite and semi‐infinite media. Copyright © 2003 John Wiley & Sons, Ltd.
An accurate scheme for mixed‐mode fracture analysis of functionally graded materials using the interaction integral and micromechanics models
Authors: Kim Jeong‐Ho , Paulino Glaucio H. 
Published: October 2003

AbstractThe interaction integral is a conservation integral that relies on two admissible mechanical states for evaluating mixed‐mode stress intensity factors (SIFs). The present paper extends this integral to functionally graded materials in which the material properties are determined by means of either continuum functions (e.g. exponentially graded materials) or micromechanics models (e.g. self‐consistent, Mori–Tanaka, or three‐phase model). In the latter case, there is no closed‐form expression for the material‐property variation, and thus several quantities, such as the explicit derivative of the strain energy density, need to be evaluated numerically (this leads to several implications in the numerical implementation). The SIFs are determined using conservation integrals involving known auxiliary solutions. The choice of such auxiliary fields and their implications on the solution procedure are discussed in detail. The computational implementation is done using the finite element method and thus the interaction energy contour integral is converted to an equivalent domain integral over a finite region surrounding the crack tip. Several examples are given which show that the proposed method is convenient, accurate, and computationally efficient. Copyright © 2003 John Wiley & Sons, Ltd.