bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular biology and immunoregulation of human neurotropic JC virus in CNS
Authors: Sweet Thersa M. , Valle Luis Del , Khalili Kamel
Published: August 2002

The human polyomavirus, JC virus (JCV), provides an excellent model system to investigate the reciprocal interaction of the immune and nervous systems. Infection with JCV occurs during childhood and the virus remains in the latent state with no apparent clinical symptoms. However, under immunosuppressed conditions, the virus enters the lytic cycle and upon cytolytic destruction of glial cells, causes the fatal demyelinating disease of the central nervous system (CNS), named progressive multifocal leukoencephalopathy (PML). In this short review, we discuss the molecular pathogenesis of PML by highlighting the role of the immune system in modulating JCV gene activation and replication, and the latency/reactivation of this virus upon immunosuppression. Further, due to the higher incidence of PML among AIDS patients, we further elaborate on the cross‐talk between JCV and HIV‐1 by direct and indirect pathways that lead to enhanced expression of the JCV genome. © 2002 Wiley‐Liss, Inc.
Glucose hydrogenation on Co–B amorphous alloy catalysts and the promoting effect of metal additives
Authors: Li Hui , Deng Jing‐Fa
Published: August 2002

Two kinds of ultrafine Co–B amorphous alloy catalysts, denoted as P‐1 Co–B and P‐2W Co–B, were prepared by chemical reduction with borohydride in aqueous or 50% (v/v) ethanol/water solution, respectively. In comparison with the corresponding Co‐based crystalline catalysts and Ni‐based catalysts, these catalysts exhibited higher activity during the liquid phase glucose hydrogenation, possibly due to the unique amorphous characteristics and the lower d‐band electron density, which was favorable for hydrogen dissociative chemisorption. Addition of Cr‐, Mo‐ or W‐promoters could further increase the conversion of Co–B amorphous catalyst, which was mainly attributed to the dispersion effect of promoters and the adsorption and polarization of carbonyl groups by these promoters. The different effects of W‐ from Cr‐ and Mo‐promoters on the conversion were observed and are discussed.

© 2001 Society of Chemical Industry
Effects of atmospheric acids on Portland cements
Authors: Derry Dennis J , Malati Mounir A , Pullen Jonathan C
Published: August 2002

Mortar prisms made from three Portland cement types, were exposed at a city centre site (London) and at a suburban site (Horsted). At each site, a set of prisms was exposed either open to the rain or sheltered from it. The chemical analysis of the cements and of the collected rainwater during the experimental period are reported, together with estimates of dry deposited pollutants. The effects of the exposure were assessed by various physical and physicochemical tests of the surface and of the bulk properties of the exposed prisms. The weight increase, the most sensitive indicator of weathering effects, was greater for the sheltered prisms than for prisms open to the rain; the latter, however, showed more visual weathering. Increase in the porosity of the mortars resulted in increased mass gain. The higher acidity of the rain at the Horsted site had an insignificant effect on the percentage mass increase. The effect of this higher acidity was reflected, though inconclusively, by the lower bulk porosity of prisms made from Sulphate Resisting Portland Cement (SRPC) exposed at the Horsted site compared with the set similarly exposed at the London site. The effect of the cement type on the properties of the tested prisms was clearest in the decrease in the ultrasonic pulse velocity (UPV) of the exposed prisms made from Portland Blast Furnace Cement (PBFC) compared with the increase in UPV in prisms made from the other two cements. It seems that the changes in the properties of the prisms exposed to the atmosphere were associated both with the products of the reaction of atmospheric acids with the cement components and the products of continued hydration beyond the 28‐day curing period.

© 2001 Society of Chemical Industry
Sonographic findings in ectopic cervical thymus in an infant
Authors: Fitoz Suat , Atasoy Çetin , Türköz Erdem , Gümüş Derya , Erden İlhan , Akyar Serdar
Published: August 2002

We present the case of a 28‐day‐old boy with ectopic thymic tissue in the neck. Sonography showed a well‐delineated, homogeneous lesion in the left submandibular region that was isoechoic relative to the mediastinal thymus. The lesion had angular margins and lacked a mass effect despite its large size (3 × 2 cm). On power Doppler imaging, arteries with an intermediate‐impedance flow pattern were seen entering the lesion from the inferior and lateral margins. On both T1‐ and T2‐weighted MR images, the lesion was isointense relative to the mediastinal thymus and had higher and lower signal intensity than muscle and fat, respectively. A sonographically guided needle biopsy confirmed the diagnosis of ectopic thymus. © 2001 John Wiley & Sons, Inc. J Clin Ultrasound 29:523–526, 2001.
Neurotransmitters and neuropeptides in the brain of the locust
Authors: Homberg Uwe
Published: August 2002

As part of continuous research on the neurobiology of the locust, the distribution and functions of neurotransmitter candidates in the nervous system have been analyzed particularly well. In the locust brain, acetylcholine, glutamate, γ‐aminobutyric acid (GABA), and the biogenic amines serotonin, dopamine, octopamine, and histamine most likely serve a transmitter function. Increasing evidence, furthermore, supports a signalling function for the gaseous molecule nitric oxide, but a role for neuroptides is so far suggested only by immunocytochemistry. Acetylcholine, glutamate, and GABA appear to be present in large numbers of interneurons. As in other insects, antennal sensory afferents might be cholinergic, while glutamate is the transmitter candidate of antennal motoneurons. GABA is regarded as the principle inhibitory transmitter of the brain, which is supported by physiological studies in the antennal lobe. The cellular distribution of biogenic amines has been analyzed particularly well, in some cases down to physiologically characterized neurons. Amines are present in small numbers of interneurons, often with large branching patterns, suggesting neuromodulatory roles. Histamine, furthermore, is the transmitter of photoreceptor neurons. In addition to these “classical transmitter substances,” more than 60 neuropeptides were identified in the locust. Many antisera against locust neuropeptides label characteristic patterns of neurosecretory neurons and interneurons, suggesting that these peptides have neuroactive functions in addition to hormonal roles. Physiological studies supporting a neuroactive role, however, are still lacking. Nitric oxide, the latest addition to the list of neurotransmitter candidates, appears to be involved in early stages of sensory processing in the visual and olfactory systems. Microsc. Res. Tech. 56:189–209, 2002. © 2002 Wiley‐Liss, Inc.
Polygonal epithelial cells in glomerular cell culture: Podocyte or parietal epithelial origin?
Authors: Yaoita Eishin , Yoshida Yutaka
Published: August 2002

Podocytes are unique cells with regard to morphology, their inability to proliferate in situ, and their apparent essential function for glomerular filtration and permselectivity. Upon transfer into culture conditions, polygonal epithelial cells grow out from isolated glomeruli and these cells have been postulated to represent dedifferentiated podocytes, even though they are negative for podocyte‐specific markers and undergo cell division. However, it is controversial whether they originate from podocytes or parietal epithelial cells (PECs) of Bowman's capsule, because isolated glomeruli contain more or less Bowman's capsule. In this review, we shall summarize recent progress in the identification of the origin of the polygonal cells and the characterization of podocytes in culture. Microsc. Res. Tech. 57:212–216, 2002. © 2002 Wiley‐Liss, Inc.
Transcytosis of plasma macromolecules in endothelial cells: A cell biological survey
Authors: Simionescu Maya , Gafencu Anca , Antohe Felicia
Published: August 2002

The modern exploration of endothelial cell biology is a largely interdisciplinary exercise. Cell biological, physiological, and more recently molecular biology approaches were used to study the pathways and the organelles involved in transcytosis of macromolecules in endothelial cell (EC). Here we discuss mainly the cell biological findings that revealed that EC have the attributes to fulfill the transport function. They are polarized cells, heterogeneous, and, thus, structurally and functionally adapted to the vascular bed in which they reside. The structural heterogeneity involves the number and distribution of plasmalemmal vesicles (caveolae), their generated channels, and the organization of intercellular junctions. The closely related functional heterogeneity comprises the degree of permeability for plasma molecules that vary as a function of organ. The EC are endowed with the cellular machinery to perform (1) endocytosis, that is to take up plasma proteins and the molecules they carry to be used for themselves (cholesterol‐carrying low density lipoproteins, fatty acid carrying albumin, iron carrying transferrin, etc.), and (2) transcytosis, which implies to transport plasma proteins to the subjacent cells and tissues. The possible pathways for transport of molecules are transcellular, via caveolae and channels, and paracellular via intercellular junctions. Most of the results obtained, so far, indicate that transcytosis of albumin, low‐density lipoproteins, metaloproteases, and insulin, is performed by cargo‐vesicles and their generated channels. The paracellular pathway can be used for water and ions; in postcapillary venules, at the level of which ∼30% of junctions are open to a space of 6 nm, small molecules may take this route. Recent data obtained by molecular biology techniques revealed that caveolae are endowed with the molecular machinery for fusion/fission, docking, and movement across cells. Moreover, the various and numerous molecules that have been detected in the caveolae membrane and the different functions assumed by this differentiated microdomain strengthen the postulate that there are at least two or more types of vesicles molecularly tailored for the local physiological requirements. Microsc. Res. Tech. 57:269–288, 2002. © 2002 Wiley‐Liss, Inc.
Functional expression and localization of P‐glycoprotein at the blood brain barrier
Authors: Bendayan Reina , Lee Gloria , Bendayan Moise
Published: August 2002

Until recently, the blood‐brain barrier was viewed as a static lipid membrane barrier. Physical attributes of the cerebral endothelial cells such as the presence of tight junctions, paucity of vesicles or caveolae, and high electrical resistance were believed to be the primary components that provide the membrane selectivity of the blood‐brain barrier to a variety of circulating compounds from the periphery. However, results from molecular biology, immunocytochemistry, biochemistry, and transport studies show that the cerebral endothelial cells possess an asymmetrical array of metabolic enzymes (i.e., alkaline phosphatase, cytochrome P450 enzymes, glutathione transferases) and energy‐dependent efflux transport proteins (i.e., P‐glycoprotein and Multidrug‐resistance proteins) that are instrumental to the barrier function. P‐glycoprotein, a membrane‐associated, energy‐dependent, efflux transporter, is expressed in brain parenchyma (i.e., astrocytes and microglia) as well as in blood‐brain and blood‐cerebrospinal fluid barriers. Its function along the blood‐brain barrier is believed to prevent the accumulation of potentially harmful compounds in the brain by actively removing them from the brain into the peripheral circulation. This is a brief review on the expression and activity of P‐glycoprotein at the blood‐brain barrier, which reports on the localization of the protein in rat brain capillaries in situ as well as in a well‐characterized in vitro model of the blood‐brain barrier, an immortalized rat brain endothelial cell line, the RBE4. Immunocytochemical analysis employing various P‐glycoprotein monoclonal antibodies, demonstrated the presence of the protein along the plasma membrane, in plasmalemmal vesicles and nuclear envelope of rat cerebral endothelial cells, both in situ and in vitro. Western blot analysis revealed a single band with a molecular weight of 170–180 kDa, a size previously reported for P‐glycoprotein, in RBE4 cells. In addition, results from functional studies show that the accumulation of the P‐glycoprotein substrate digoxin by RBE4 monolayer cells is significantly enhanced in the presence of standard P‐glycoprotein inhibitors (verapamil, cyclosporin A, PSC 833), protease inhibitors (saquinavir, ritonavir, indinavir), and the metabolic inhibitor, sodium azide. These results demonstrate the functional expression of P‐glycoprotein in the immortalized rat brain endothelial cell line, RBE4. Novel in situ and in vitro intracellular locations of P‐glycoprotein in cerebral endothelial cells have been identified suggesting that this transporter may play a significant role in the subcellular distribution of substrates in the brain. Microsc. Res. Tech. 57:365–380, 2002. © 2002 Wiley‐Liss, Inc.
Expression of transcription factors during oligodendroglial development
Authors: Wegner Michael
Published: August 2002

Transcription factors coordinate the orderly changes of gene expression that underlie all developmental processes including those of oligodendrocytes. In comparison to other systems, relatively little is known about the role of transcription factors during oligodendrocyte development. However, recent years have seen the identification of oligodendroglial transcription factors that, not surprisingly, belong to the same gene families that are also important in other tissues or cell lineages. Some transcription factors such as the bHLH (basic helix‐loop‐helix) proteins Olig‐1 and Olig‐2 or the high‐mobility‐group protein Sox10 are expressed already early during development of the oligodendrocyte lineage, whereas expression of other transcription factors such as the homeodomain protein Gtx/Nkx6.2 only start at the time of terminal differentiation. Once turned on, expression of these proteins can either be permanent as in the above‐mentioned cases or transient as exemplified by the POU domain proteins Tst‐1/Oct6/SCIP, Brn‐1 and Brn‐2. Analyses of these transcription factors has already led to the identification of important principles such as functional redundancy between co‐expressed proteins, unexpected divergence in the transcription factor repertoire of oligodendrocytes and Schwann cells, and equally unsuspected similarities in transcription factor usage between oligodendrocytes and neurons. Although so far only a small percentage of oligodendroglial transcription factors has been identified, these are excellent candidates for regulators of cell type specification, lineage progression, and terminal differentiation. Microsc. Res. Tech. 52:746–752, 2001. © 2001 Wiley‐Liss, Inc.
Immunopathogenesis of delayed‐type hypersensitivity
Authors: Kobayashi Kazuo , Kaneda Kenji , Kasama Tsuyoshi
Published: August 2002

Cell‐mediated immunity is defined as a beneficial host response characterized by an expanded population of specific T cells, which, in the presence of antigens, produce cytokines locally. The activation and recruitment of cells into an area of inflammation is a crucial step in the development of DTH responses. DTH is immunologically a process similar to cell‐mediated immunity, involving T cells and cytokines. CD4 T helper (Th) 1 cells, differentiated from naive Th cells by IL‐12 and IL‐18 produced from macrophages, play a regulatory role in the expression of DTH and activation of macrophages via interferon γ generated by Th1 and natural killer cells. Macrophages accumulate at the site of DTH and become activated through the CD4 Th1 cell‐cytokine‐macrophage axis. However, DTH leads to pathologic responses, such as granulomatous inflammation, calcification, caseation necrosis, and cavity formation. Granulomas usually form as a result of the persistence of a nondegradable product or as the result of DTH responses. DTH is also required for host defense against etiologic agents, such as Mycobacterium tuberculosis. The expression of cell‐mediated immunity/DTH is a double‐edged sword that may contribute to both clearance of the etiologic agent and tissue damage. Microsc. Res. Tech. 53:241–245, 2001. © 2001 Wiley‐Liss, Inc.
Role of dendritic cells and Th2 lymphocytes in asthma: Lessons from eosinophilic airway inflammation in the mouse
Authors: Van Rijt Leonie S. , Lambrecht Bart N.
Published: August 2002

Asthma is a chronic disorder of the airways characterized by variable airway narrowing, mucus hypersecretion, and infiltration of the airway wall with eosinophils. It is now believed that asthma is controlled by Th2 lymphocytes producing cytokines such as IL‐4, IL‐5, IL‐9, and IL‐13. Animal models of eosinophilic airway inflammation and airway hyperreactivity have been developed to study the contribution of cells or mediators in the pathogenesis of asthma. In this review, we discuss the role of antigen presenting cells, CD4+ and CD8+ T lymphocytes, B lymphocytes, NK cells, and mast cells in the induction and maintenance of eosinophilic airway inflammation, mucus hypersecretion, and airway hyperreactivity. Microsc. Res. Tech. 53:256–272, 2001. © 2001 Wiley‐Liss, Inc.
Energy expenditure and testosterone in free‐living male yellow‐pine chipmunks
Authors: Place Ned J. , Veloso Claudio , Visser G.H. , Kenagy G.J.
Published: August 2002

The onset of mating in yellow‐pine chipmunks (Tamias amoenus) follows emergence from a prolonged period of energy conservation during hibernation. Energy expenditures are greatly accelerated to meet the demands of the reproductive season. When emerging from hibernation, typical male chipmunks (breeders) have enlarged testes and a high level of plasma testosterone (T). However, certain males that do not participate in reproduction (nonbreeders) maintain small testes and low plasma T levels and emerge several weeks later than the breeders. The timing of the terminal arousal from hibernation and onset of mating are associated with increased plasma T levels. Experimental elevation of T levels in T. amoenus outside the mating season has been associated with a decrease in body mass, further suggesting an effect of T on energy balance. To test this hypothesis, we measured daily energy expenditure (DEE) in free‐living, nonbreeding male chipmunks in the presence and absence of a T‐implant. We also measured DEE in breeding males when endogenous T levels were high. DEE of the nonbreeders was not affected by our manipulation of plasma T, and the DEE of breeding males did not differ from that of nonbreeders. We conclude that energy expenditure on a daily basis in male yellow‐pine chipmunks is not influenced by levels of T. However, on a seasonal basis, the earlier emergence from hibernation by breeding males, which appears to be influenced by T, represents an overall seasonal energy expenditure that exceeds that of nonbreeding males. J. Exp. Zool. 292:460–467, 2002. © 2002 Wiley‐Liss, Inc.
Ammonia excretion and urea handling by fish gills: present understanding and future research challenges
Authors: Wilkie Michael Patrick
Published: August 2002

In fresh water fishes, ammonia is excreted across the branchial epithelium via passive NH3 diffusion. This NH3 is subsequently trapped as NH in an acidic unstirred boundary layer lying next to the gill, which maintains the blood‐to‐gill water NH3 partial pressure gradient. Whole animal, in situ, ultrastructural and molecular approaches suggest that boundary layer acidification results from the hydration of CO2 in the expired gill water, and to a lesser extent H+ excretion mediated by apical H+‐ATPases. Boundary layer acidification is insignificant in highly buffered sea water, where ammonia excretion proceeds via NH3 diffusion, as well as passive NH diffusion due to the greater ionic permeability of marine fish gills. Although Na+/H+ exchangers (NHE) have been isolated in marine fish gills, possible Na+/NH exchange via these proteins awaits evaluation using modern electrophysiological and molecular techniques. Although urea excretion (JUrea) was thought to be via passive diffusion, it is now clear that branchial urea handling requires specialized urea transporters. Four urea transporters have been cloned in fishes, including the shark kidney urea transporter (shUT), which is a facilitated urea transporter similar to the mammalian renal UT‐A2 transporter. Another urea transporter, characterized but not yet cloned, is the basolateral, Na+ dependent urea antiporter of the dogfish gill, which is essential for urea retention in ureosmotic elasmobranchs. In ureotelic teleosts such as the Lake Magadi tilapia and the gulf toadfish, the cloned mtUT and tUT are facilitated urea transporters involved in JUrea. A basolateral urea transporter recently cloned from the gill of the Japanese eel (eUT) may actually be important for urea retention during salt water acclimation. A multi‐faceted approach, incorporating whole animal, histological, biochemical, pharmacological, and molecular techniques is required to learn more about the location, mechanism of action, and functional significance of urea transporters in fishes. © 2002 Wiley‐Liss, Inc.
Mannan‐degrading enzymes purified from the crop of the brown garden snail Helix aspersa Müller (Gastropoda Pulmonata)
Authors: Charrier Maryvonne , Rouland Corinne
Published: August 2002

Two mannan‐degrading enzymes were purified from the crop of the terrestrial snail Helix aspersa Müller. The crude extracts were taken from dormant (for 4 months) snails. The enzymes were a βD‐mannanase of 37.4 ± 0.3 kDa (EC 3.2.1.78) and a βD‐mannosidase of 77.8 ± 1.9 kDa (EC 3.2.1.25). Both enzymes degraded insoluble mannan, releasing either mannose only (β‐mannosidase) or oligosaccharides, possibly mannotriose and mannopentaose (β‐mannanase). The β‐mannanase had a typical endo‐activity pattern, while the β‐mannosidase was an exoenzyme. The incubation of both enzymes with mannan increased the catalysis by 83%. The best synergy was found with 75% mannosidase combined with 25% mannanase. The β‐mannanase also hydrolysed β‐linked heteromannans and its affinity for different galactomannans was studied. The Km values, varying from 2.89 ± 0.47 mg × ml–1 to 0.26 ± 0.01 mg × ml–1, revealed the inhibitory effect of the αD‐galactosyl residues released. The β‐mannosidase was acidic (optimum pH = 3.3) and heat‐sensitive (50% residual activity at 42°C after 5 min of pre‐incubation), while the β‐mannanase remained stable until 48.5°C (50% residual activity) and over a pH range of 4.3–7.5. The properties of these mannanolytic enzymes are discussed in this paper compared with those purified in other gastropods and in a bacterium, Enterococcus casseliflavus, a quite similar strain previously isolated from this snail intestine. The occurrence of thermostable enzymes in H. aspersa digestive tract could be a zootechnic parameter of great importance for snail farming. J. Exp. Zool. 290:125–135, 2001. © 2001 Wiley‐Liss, Inc.
Varieties of modules: Kinds, levels, origins, and behaviors
Authors: Winther Rasmus G.
Published: August 2002

This article began as a review of a conference, organized by Gerhard Schlosser, entitled “Modularity in Development and Evolution.” The conference was held at, and sponsored by, the Hanse Wissenschaftskolleg in Delmenhorst, Germany in May, 2000. The article subsequently metamorphosed into a literature and concept review as well as an analysis of the differences in current perspectives on modularity. Consequently, I refer to general aspects of the conference but do not review particular presentations. I divide modules into three kinds: structural, developmental, and physiological. Every module fulfills none, one, or multiple functional roles. Two further orthogonal distinctions are important in this context: module‐kinds versus module‐variants‐of‐a‐kind and reproducer versus nonreproducer modules. I review criteria for individuation of modules and mechanisms for the phylogenetic origin of modularity. I discuss conceptual and methodological differences between developmental and evolutionary biologists, in particular the difference between integration and competition perspectives on individualization and modular behavior. The variety in views regarding modularity presents challenges that require resolution in order to attain a comprehensive, rather than a piecemeal and fragmentary, evolutionary developmental biology. J. Exp. Zool. (Mol. Dev. Evol.) 291:116–129, 2001. © 2001 Wiley‐Liss, Inc.
Persistence of oviposition rhythm in individuals of Drosophila melanogaster reared in an aperiodic environment for several hundred generations
Authors: Sheeba V. , Chandrashekaran M.K. , Joshi Amitabh , Sharma Vijay Kumar
Published: August 2002

The oviposition rhythm of individual flies of Drosophila melanogaster from a population maintained in an aperiodic environment (with light, temperature, humidity, and other factors which could provide time cues, kept constant) for several hundred generations was assayed in constant light (LL), in light/dark (LD 12:12 hr) cycle, and in constant darkness (DD). More than 50% of the flies assayed exhibited rhythmicity in oviposition in all three light regimes. The results indicate that the phenomenon of egg laying is rhythmic in individual D. melanogaster females and is controlled by an endogenous time keeping mechanism. The persistence of the oviposition rhythm in a large proportion of individuals in the population after several hundred generations of rearing in a constant environment strengthens the view that possessing biological clocks may confer some intrinsic fitness advantage even to organisms living in aperiodic environments. J. Exp. Zool. 290:541–549, 2001. © 2001 Wiley‐Liss, Inc.
Theory of the growth and evolution of feather shape
Authors: Prum Richard O. , Williamson Scott
Published: August 2002

We present the first explicit theory of the growth of feather shape, defined as the outline of a pennaceous feather vane. Based on a reanalysis of data from the literature, we propose that the absolute growth rate of the barbs and rachis ridges, not the vertical growth rate, is uniform throughout the follicle. The growth of feathers is simulated with a mathematical model based on six growth parameters: (1) absolute barb and rachis ridge growth rate, (2) angle of helical growth of barb ridges, (3) initial barb ridge number, (4) new barb ridge addition rate, (5) barb ridge diameter, and (6) the angle of barb ramus expansion following emergence from the sheath. The model simulates growth by cell division in the follicle collar and, except for the sixth parameter, does not account for growth by differentiation in cell size and shape during later keratinization. The model can simulate a diversity of feather shapes that correspond closely in shape to real feathers, including various contour feathers, asymmetrical feathers, and even emarginate primaries. Simulations of feather growth under different parameter values demonstrate that each parameter can have substantial, independent effects on feather shape. Many parameters also have complex and redundant effects on feather shape through their influence on the diameter of the follicle, the barb ridge fusion rate, and the internodal distance. Simulated isochrones—the loci, or sets, of feather cells of the same age—have the same oblique chevron‐shaped position in the mature feather as fault bars, which are isochronic defects in the barbules created by a disruptions during development. Accurate simulation of fault bar shape and position confirms the uniform absolute growth rate hypothesis and the general realism of the model. The theory defines a six‐parameter feather morphospace, and provides many predictions about the developmental determination of feather shape that can be tested with detailed observations and experiments on developing feathers. This theory also provides testable predictions about the changes in developmental mechanisms required to evolve different feather shapes to accomplish various functions. J. Exp. Zool. (Mol. Dev. Evol.) 291:30–57, 2001. © 2001 Wiley‐Liss, Inc.
Tiled partial cubes
Authors: Brešar Boštjan , Imrich Wilfried , Klavžar Sandi , Mulder Henry Martyn , Škrekovski Riste
Published: August 2002

In the quest to better understand the connection between median graphs, triangle‐free graphs and partial cubes, a hierarchy of subclasses of partial cubes has been introduced. In this article, we study the role of tiled partial cubes in this scheme. For instance, we prove that almost‐median graphs are tiled and that tiled partial cubes are semi‐median. We also describe median graphs as tiled partial cubes without convex Q and extend an inequality for median graphs to a larger subclass of partial cubes. © 2002 Wiley Periodicals, Inc. J Graph Theory 40: 91–103, 2002
Innovative and important, yes, but also instrumental and incomplete: the treatment of redistribution in the new ‘New Poverty Agenda’
Authors: Maxwell Simon
Published: August 2002

The current narrative on poverty reduction, summarized in WDR 2000/1, rehabilitates distribution as a central topic on the development agenda. WDR argues (i) that redistribution matters for instrumental reasons, as a route to faster growth and faster poverty reduction; (ii) that changes to income distribution result from complex changes in sectoral, geographical and individual performance; and (iii) that better distribution can be achieved in a win‐win fashion, without undermining incentives or forcing a choice between equity and efficiency. The argument can be extended: (i) the case for redistribution is not simply instrumental, but can be rooted in a discourse about social inclusion and rights; (ii) observed changes are strongly associated with liberalization policies, and with changes to social norms; and (iii) governments can do more than the Bank suggests to achieve greater equality. A commitment to redistribution should be enshrined in a new international development target: a ceiling on Gini coefficients of 0.45. Copyright © 2001 John Wiley & Sons, Ltd.
Neurostimulation systems for deep brain stimulation: In vitro evaluation of magnetic resonance imaging–related heating at 1.5 tesla
Authors: Rezai Ali R. , Finelli Daniel , Nyenhuis John A. , Hrdlicka Greg , Tkach Jean , Sharan Ashwini , Rugieri Paul , Stypulkowski Paul H. , Shellock Frank G.
Published: August 2002

Purpose

To assess magnetic resonance imaging (MRI)‐related heating for a neurostimulation system (Activa® Tremor Control System, Medtronic, Minneapolis, MN) used for chronic deep brain stimulation (DBS).

Materials and Methods

Different configurations were evaluated for bilateral neurostimulators (Soletra® Model 7426), extensions, and leads to assess worst‐case and clinically relevant positioning scenarios. In vitro testing was performed using a 1.5‐T/64‐MHz MR system and a gel‐filled phantom designed to approximate the head and upper torso of a human subject. MRI was conducted using the transmit/receive body and transmit/receive head radio frequency (RF) coils. Various levels of RF energy were applied with the transmit/receive body (whole‐body averaged specific absorption rate (SAR); range, 0.98–3.90 W/kg) and transmit/receive head (whole‐body averaged SAR; range, 0.07–0.24 W/kg) coils. A fluoroptic thermometry system was used to record temperatures at multiple locations before (1 minute) and during (15 minutes) MRI.

Results

Using the body RF coil, the highest temperature changes ranged from 2.5°–25.3° C. Using the head RF coil, the highest temperature changes ranged from 2.3°–7.1° C.Thus, these findings indicated that substantial heating occurs under certain conditions, while others produce relatively minor, physiologically inconsequential temperature increases.

Conclusion

The temperature increases were dependent on the type of RF coil, level of SAR used, and how the lead wires were positioned. Notably, the use of clinically relevant positioning techniques for the neurostimulation system and low SARs commonly used for imaging the brain generated little heating. Based on this information, MR safety guidelines are provided. These observations are restricted to the tested neurostimulation system. J. Magn. Reson. Imaging 2002;15:241–250. © 2002 Wiley‐Liss, Inc.
Modulation of cerebral blood oxygenation by indomethacin: MRI at rest and functional brain activation
Authors: Bruhn Harald , Fransson Peter , Frahm Jens
Published: August 2002

The modulation of blood oxygenation level‐dependent (BOLD) cerebral MRI contrast by the vasoconstrictive drug indomethacin (i.v. 0.2 mg/kg b.w.) was investigated in 10 healthy young adults without and with functional challenge (repetitive and sustained visual activation). For comparison, isotonic saline (placebo, 20 mL) and acetylsalicylate (i.v. 500 mg) were investigated as well, each in separate sessions using identical protocols. After indomethacin, dynamic T2*‐weighted echo‐planar MRI at 2.0 T revealed a rapid decrease in MRI signal intensity by 2.1%–2.6% in different gray matter regions (P ≤ 0.001 compared to placebo), which was not observed for acetylsalicylate and the placebo condition. Regional signal differences were not significant within gray matter, but all gray matter regions differed significantly from the signal decrease of only 1.2% ± 0.7% observed in white matter (P = 0.001). For the experimental parameters used, a 1% MRI signal decrease in response to indomethacin was estimated to correlate with a decrease of the cerebral blood flow by about 12 ml/100 g/minute, and an increase of the oxygen extraction fraction by about 15%. Responses to visual activation were not affected by saline or acetylsalicylate, and yielded 5.0%–5.5% BOLD MRI signal increases both before and after drug application. In contrast, indomethacin reduced the initial response strength to 82%–85% of that obtained without the drug. The steady‐state response during sustained activation reached only 47% of the corresponding pre‐drug level (P < 0.01). During repetitive activation the BOLD contrast was reduced to 66% of that observed for control conditions (P < 0.001). In conclusion, indomethacin attenuates the vasodilatory force at functional brain activation, indicating different mechanisms governing neurovascular coupling. J. Magn. Reson. Imaging 2001;13:325–334. © 2001 Wiley‐Liss, Inc.
A multi‐scale method for automatic correction of intensity non‐uniformity in MR images
Authors: Han Chao , Hatsukami Thomas S. , Yuan Chun
Published: August 2002

In this paper, a novel multi‐scale method for coil sensitivity profile correction is presented based on wavelet transform. A magnetic resonance (MR) image can be decomposed into two spaces by the wavelet transform: approximate space and residual space. The approximate templates in approximate space can be thought of as multi‐scale sensitivity profiles of the surface coil for coil correction. When we choose a suitable filter for decomposition, one of the sensitivity profiles should be optimal among the multi‐scale sensitivity profiles. The optimal sensitivity profile can be chosen automatically by an analysis of the contents of the two spaces. The multi‐scale method does not rely on any data other than the image generated by the MR scanner. The experiment showed promising results based on one‐dimensional simulation and images of phantom and human images. J. Magn. Reson. Imaging 2001;13:428–436. © 2001 Wiley‐Liss, Inc.
Examination of intra‐gastrointestinal tract signal elimination in MRCP: Combined use of T1‐shortening positive contrast agent and single‐shot fast inversion recovery
Authors: Kato Joji , Kawamura Yoshihiko , Watanabe Tsuneo , Okada Susumu , Cho Keiichi , Ishihara Makiko
Published: August 2002

To examine the effects of removing the gastrointestinal signal in MR cholangiopancreatography (MRCP), investigations were carried out on the combined use of T1‐shortening intestine‐positive contrast medium, FerriSeltz with ferric ammonium citrate as the main component, and high‐speed imaging using single‐shot fast inversion recovery (SSFIR). The contrast effect was significantly elevated to 10.2 ± 1.6 after administration, compared with 5.9 ± 2.4 before administration (P < 0.001). The enhancement effect was also significantly elevated to 13.2 ± 3.0 after administration, compared with 4.9 ± 3.1 before administration (P < 0.001). These results were obtained because the null point of FerriSeltz aqueous solution (5.97 mmol/L) was in the range of approximately 180 msec. With the present method, adequate suppression of the signal intensity of the digestive tract was obtained relatively easily with MRCP, and the technique was found to be effective. J. Magn. Reson. Imaging 2001;13:738–743. © 2001 Wiley‐Liss, Inc.
Determination of arterial input function using fuzzy clustering for quantification of cerebral blood flow with dynamic susceptibility contrast‐enhanced MR imaging
Authors: Murase Kenya , Kikuchi Keiichi , Miki Hitoshi , Shimizu Teruhiko , Ikezoe Junpei
Published: August 2002

An accurate determination of the arterial input function (AIF) is necessary for quantification of cerebral blood flow (CBF) using dynamic susceptibility contrast‐enhanced magnetic resonance imaging. In this study, we developed a method for obtaining the AIF automatically using fuzzy c‐means (FCM) clustering. The validity of this approach was investigated with computer simulations. We found that this method can automatically extract the AIF, even under very noisy conditions, e.g., when the signal‐to‐noise ratio is 2. The simulation results also indicated that when using a manual drawing of a region of interest (ROI) (manual ROI method), the contamination of surrounding pixels (background) into ROI caused considerable overestimation of CBF. We applied this method to six subjects and compared it with the manual ROI method. The CBF values, calculated using the AIF obtained using the manual ROI method [CBF(manual)], were significantly higher than those obtained with FCM clustering [CBF(fuzzy)]. This may have been due to the contamination of non‐arterial pixels into the manually drawn ROI, as suggested by simulation results. The ratio of CBF(manual) to CBF(fuzzy) ranged from 0.99–1.83 [1.31 ± 0.26 (mean ± SD)]. In conclusion, our FCM clustering method appears promising for determination of AIF because it allows automatic, rapid and accurate extraction of arterial pixels. J. Magn. Reson. Imaging 2001;13:797–806. © 2001 Wiley‐Liss, Inc.
BOLD MRI of human tumor oxygenation during carbogen breathing
Authors: Taylor N. Jane , Baddeley Hiram , Goodchild Kate A. , Powell Melanie E. B. , Thoumine Michelle , Culver Linda A. , Stirling J. James , Saunders Michele I. , Hoskin Peter J. , Phillips Heather , Padhani Anwar R. , Griffiths John R.
Published: August 2002

An MRI method is described for demonstrating improved oxygenation of human tumors and normal tissues during carbogen inhalation (95% O2, 5% CO2). T‐weighted gradient‐echo imaging was performed before, during, and after carbogen breathing in 47 tumor patients and 13 male volunteers. Analysis of artifacts and signal intensity was performed. Thirty‐six successful tumor examinations were obtained. Twenty showed significant whole‐tumor signal increases (mean 21.0%, range 6.5–82.4%), and one decreased (−26.5 ± 8.0%). Patterns of signal change were heterogeneous in responding tumors. Five of 13 normal prostate glands (four volunteers and nine patients with nonprostatic tumors) showed significant enhancement (mean 11.4%, range 8.4–14.0%). An increase in brain signal was seen in 11 of 13 assessable patients (mean 8.0 ± 3.7%, range 5.0–11.7%). T‐weighted tumor MRI during carbogen breathing is possible in humans. High failure rates occurred due to respiratory distress. Significant enhancement was seen in 56%, suggesting improved tissue oxygenation and blood flow, which could identify these patients as more likely to benefit from carbogen radiosensitization. J. Magn. Reson. Imaging 2001;14:156–163. © 2001 Wiley‐Liss, Inc.
An introduction to quadrupole–time‐of‐flight mass spectrometry
Authors: Chernushevich Igor V. , Loboda Alexander V. , Thomson Bruce A.
Published: August 2002

A brief introduction is presented to the basic principles and application of a quadrupole–time‐of‐flight (TOF) tandem mass spectrometer. The main features of reflecting TOF instruments with orthogonal injection of ions are discussed. Their operation and performance are compared with those of triple quadrupoles with electrospray ionization and matrix‐assisted laser desorption/ionization (MALDI) TOF mass spectrometers. Examples and recommendations are provided for all major operational modes: mass spectrometry (MS) and tandem MS (MS/MS), precursor ion scans and studies of non‐covalent complexes. Basic algorithms for liquid chromatography/MS/MS automation are discussed and illustrated by two applications. Copyright © 2001 John Wiley & Sons, Ltd.
In‐source fragmentation of peptide aldehydes and acetals: influence of peptide length and charge state
Authors: Buré Corinne , Gobert Wilfried , Lelièvre Dominique , Delmas Agnès
Published: August 2002

The use of in‐source collision‐induced dissociation (CID) was evaluated to generate structural information on peptide aldehydes, which represent an important class of compounds as inhibitors for serine and cysteine proteases and as key intermediates for protein engineering. By studying five peptide aldehydes of different lengths, and their peptide acetal counterparts, mass to charge (m/z) dependency of in‐source fragmentation was established for peptides that differ only by their C‐terminal functionalization. In‐source fragmentation of peptide aldehydes and acetals leads to the same final ion, probably via a similar mechanism. Moreover, the gas‐phase information obtained here reflects the equilibrium occurring in solution between the peptide aldehyde and its hydrated form, which was retained during the ionization process. The equilibrium constant was determined to be close to unity. Disturbance of this equilibrium should enable the stability of covalent hydration of a given series of aldehydes to be compared. Copyright © 2001 John Wiley & Sons, Ltd.
Conformational antigenic determinants generated by interactions between a bacterially expressed recombinant peptide of the hepatitis E virus structural protein
Authors: Zhang Ji‐Zhong , Ng Mun H. , Xia N. S. , Lau S. H. , Che X. Y. , Chau T. N. , Lai S. T. , Im Stanley W. K.
Published: August 2002

A 23 kDa peptide locating to amino acid residues 394 to 604 of the major Hepatitis E Virus (HEV) structural protein was expressed in E. coli. This peptide was found to interact naturally with one another to form homodimers and it was recognized strongly and commonly in its dimeric form by HEV reactive human sera. The antigenic activity associated with the dimeric form was abrogated when the dimer was dissociated into monomer and the activity was reconstituted after the monomer was re‐associated into dimer again. The dimeric form of the peptide elicited a vigorous antibody response in experimental animals and the resulting antisera were found to cross‐react against HEV, effecting an efficient immune capture of the virus. These results attributed the antigenic activity associated with the dimeric form of the peptide to conformational antigenic determinants generated as a result of interaction between the peptide molecules. It is suggested that some of these antigenic determinants may be expressed by the HEV capsid and raised the possibility of this bacterially expressed peptide as an HEV vaccine candidate. J. Med. Virol. 64:125–132, 2001. © 2001 Wiley‐Liss, Inc.
Identification of the 5′ terminal sequence of the SAR‐55 and MEX‐14 strains of hepatitis E virus and confirmation that the genome is capped
Authors: Zhang Mingdong , Purcell Robert H. , Emerson Suzanne U.
Published: August 2002

Hepatitis E virus (HEV) is a nonenveloped virus with a genome of single‐stranded, positive‐sense RNA. The 5′ terminal sequence of two HEV strains (SAR‐55 and MEX‐14) was determined by a 5′ RNA ligase‐mediated rapid amplification of cDNA ends (RACE) method designed to select capped RNAs. The 5′ noncoding region of the SAR‐55 and MEX‐14 strains were amplified, confirming that the genomic RNA of HEV is capped. The 5′ noncoding region of the SAR‐55 strain had 25 nucleotides, which is two less than reported for the Burmese strain, and that of the MEX‐14 strain had 24 nucleotides, which is 21 more than reported previously [Huang et al., 1992]. J. Med. Virol. 65:293–295, 2001. © 2001 Wiley‐Liss, Inc.
Amino acid and phenotypic changes in dengue 2 virus associated with escape from neutralisation by IgM antibody
Authors: Lok Shee Mei , Ng Mah Lee , Aaskov John
Published: August 2002

Two dengue 2‐specific IgM monoclonal antibodies (MAb) recognised spatially unrelated epitopes on the envelope (E) protein of dengue 2 virus, which were also recognised by serum from 20 and 50%, respectively, of patients with a primary dengue 2 infection. Dengue 2 virus populations escaping neutralisation by MAb 6B2 (representing the majority population of dengue 2‐specific IgM MAbs ) had a deduced amino acid change (G‐S) in the pre‐Membrane (prM) protein at position 15 and a second in the E protein at E311 (E‐G). The change in the E protein was adjacent to the only other epitopes on dengue 2 virus (E307, E383‐385) involved in neutralisation that have been identified but that were recognised by IgG antibodies. Dengue 2 virus escaping neutralisation by IgM MAb 10F2, representing the minority population of dengue 2‐specific IgM MAbs, had the same deduced amino acid change (G‐S) at prM15 as the 6B2 neutralisation escape mutant dengue 2 virus population and four deduced amino acid changes in the E protein (E69, T‐I, in the glycosylation motif; E71, E‐D; E112, S‐G; E124, I‐N), which may be close enough to each other to form a single epitope and a fifth at E402 (F‐L) in a region of the E protein of TBE virus essential for the low pH‐induced E protein dimer‐trimer transition. The 10F2 neutralisation escape mutant, but not the 6B2 one, had lost its ability to cause fusion from within Aedes albopictus mosquito cells and was inactivated more rapidly than the 6B2 neutralisation escape mutant and wild type viruses at 42°C. Dengue 2 viruses passaged in BHK cells in the absence of a selecting antibody, shared a common amino acid (S) at E53, which differed from both wild type and neutralisation escape mutant virus populations at this position (P) and may have been responsible for a significant reduction in the ability of these “passage control” virus populations to be neutralised by both 6B2 and 10F2 antibodies. J. Med. Virol. 65:315–323, 2001. © 2001 Wiley‐Liss, Inc.