bluuebunny/crossref_metadata_2025 huggingface dataset:
Density‐of‐states function in metal‐free phthalocyanine: effect of exposure to chlorodifluoromethane
Authors: Zhivkov I. , Danev G. , Nešpůrek S. , Sworakowski J.
Published: May 2004

Changes in the energy structure of local states during the exposure of metal‐free phthalocyanine films to chlorodifluoromethane were studied using the technique of thermomodulated space‐charge‐limited currents. The broadening of the energy distribution of the states is explained on the basis of charge‐dipole interactions.
Correlation between large polarons in molecular chains
Authors: Brizhik Larissa , Eremko Alexander
Published: May 2004

We studied few extra electrons in a molecular chain with respect of electron‐phonon coupling in the adiabatic approximation. It is shown that the lowest state of two extra electrons in a chain corresponds to the singlet bisoliton state with one deformational potential well. Two electrons with parallel spins form a localised triplet state, which corresponds to the two‐hump charge distribution function. Three extra electrons form an almost independent nonlinear superposition of a soliton and bisoliton states. In the case of four electrons, the two almost independent bisolitons are formed. These two states tend to separate in the chain at the maximal distance due to the Fermi repulsion, accounted for in the zero‐order adiabatic approximation. This repulsion is partly compensated by the attraction between the solitons due to their exchange with virtual phonons, described by the non‐adiabatic part of the Hamiltonian. The formation of solitons is characterised by the appearance of the bound soliton and bisoliton levels in the forbidden energy band. This constitutes the qualitative difference of the large polaron (soliton) states from the almost free electron states and small polaron states.
Organic electroluminescent devices using europium complex‐doped poly(N‐vinylcarbazole)
Authors: Li Tingxi , Fukuyama Hidehito , Yamagata Yoshinori , Lan Hsing‐Lin , Kido Junji
Published: May 2004

Electroluminescence (EL) properties of europium (Eu) complex‐doped poly(N‐vinylcarbazole) (PVK) were investigated. A device structure of glass substrate/indium‐tin oxide/hole‐injection layer/Eu complex‐doped PVK/hole‐blocking layer/electron transport layer/electron‐injection layer/Al was employed. Red emission originating from Eu complex was observed. Relatively high luminance of 50 cd/m2 and an efficiency of 0.2% were obtained. Copyright © 2004 John Wiley & Sons, Ltd.
Asymmetric hydrogenation of ketones catalyzed by silica‐supported chitosan‐iron‐nickel complex
Authors: Zhou Da‐Qing , Zhou De‐Jun , Cui Xiao‐Hua , Wang Fu‐Ming , Huang Mei‐Yu , Jiang Ying‐Yan
Published: May 2004

A new silica‐supported biopolymer‐metal complex, silica‐supported chitosan‐iron‐nickel complex was prepared by a very simple method. This complex catalyst can be used as a catalyst in the asymmetric hydrogenation of propiophenone to (R)‐(+)‐1‐phenyl‐1‐propanol and acetophenone to (R)‐(+)‐1‐phenyl ethanol in 91.7 and 77.7% optical yields, respectively, at 110°C and under 70 kg/cm2 pressure. The catalyst could be reused several times without any remarkable change in the catalytic activity. Copyright © 2004 John Wiley & Sons, Ltd.
Reactive melt blends of thermoplastic polyolefins, MAH‐g‐PP and nylon 6
Authors: Kim Min Soo , Kim Byung Kyu
Published: May 2004

Reactive melt blends of an ethylene‐propylene‐diene terpolymer (EPDM) based thermoplastic elastomer (TPE), maleic anhydride grafted polypropylene (MAH‐g‐PP), and nylon 6 were prepared in a single screw extruder and evaluated in terms of morphological, rheological, thermal, dynamic mechanical, and mechanical properties of the blends. It was found that MAH‐g‐PP‐co‐nylon 6 copolymers were in situ formed and acted as effective compatibilizers for polypropylene (PP) and nylon 6. Phase separation of PP and EPDM in TPE increased with the addition and increasing amount of MAH‐g‐PP and nylon 6, leading to decreased glass transition temperature (Tg) of TPE and increased crystalline melting temperature (Tm) of PP. Copyright © 2004 John Wiley & Sons, Ltd.
The basic research on physiological property of functionalized hyaluronan—I. Effect of hyaluronan and sulfated hyaluronan on cell proliferation of human epidermal keratinocytes
Authors: Satoh Takashi , Nagahata Misao , Teramoto Akira , Hatimori Akira , Abe Koji , Im Seung Soon
Published: May 2004

Hyaluronan (HA) is one of the polysaccharides that is found widely in connective tissue of mammals, and it has no sulfate group and high molecular weight in comparison with other glycosaminoglycans. Glycosaminoglycans are deeply concerned with the manifestation of biofunctions not only by their physical properties but also by physiological ones. In this study, sulfated HA (S‐HA) with various degrees of sulfate substitution and high molecular weight will be synthesized in order to give HA new biological functions. Moreover, the effect of HA and S‐HA on cell proliferation of human epidermal keratinocytes in vitro will be discussed. HA did not affect lag phase, but growth rate (metabolic turnover) of the cell in a logarithmic growth phase which was controlled by the molecular weight of HA. S‐HA stimulated the cell proliferation in the low concentration region under 1 μg/ml. While it inhibited the cell proliferation in the high concentration region over 10 μg/ml. It strongly suppressed the cell proliferation in the logarithmic growth metaphase. These facts were considered to be caused by the change of the cell‐matrix and/or cell–cell interactions. Copyright © 2004 John Wiley & Sons, Ltd.
Glucose oxidase electrodes of polyaniline, poly(o‐toluidine) and their copolymer as a biosensor: a comparative study
Authors: Borole D. D. , Kapadi U. R. , Mahulikar P. P. , Hundiwale D. G.
Published: May 2004

A simple technique is described for constructing a glucose sensor by the entrapment of glucose oxidase (GOD) in a polyaniline (PA), poly(o‐toluidine) (POT) and their copolymer poly(aniline‐co‐o‐toluidine) (PA‐co‐POT) thin films, which were electrochemically deposited on a platinum plate in phosphate and acetate buffer. The maximum current response was observed for PA, POT, and PA‐co‐POT GOD electrodes at pH 5.5 and potential 0.60 V (v. Ag/AgCl). The phosphate buffer gives fast response as compared to acetate buffer in amperometric measurements. PA GOD electrode shows the fastest response followed by PA‐co‐POT and POT GOD electrodes. Copyright © 2004 John Wiley & Sons, Ltd.
Molecular design, synthesis, and nonlinear optical properties of novel T‐type polyimides with exceptionally high thermal stability of the second harmonic generation
Authors: Lee Ju‐Yeon , Bang Han‐Bae , Park Eun‐Ju , Rhee Bum Ku , Lee Seung Mook , Lee Jin Hyun
Published: May 2004

2,5‐Bis‐(3,4‐dicarboxyphenylcarboxyethoxy)‐4′‐nitrostilbene dianhydride was prepared and reacted with 1,4‐phenylenediamine, 4,4′‐oxydianiline, 4,4′‐diaminobenzanilide, and 4,4′‐(hexafluoroisopropylidene)dianiline to yield unprecedented novel T‐type polyimides (4–7) containing 2,5‐dioxynitrostilbenyl groups as nonlinear optical chromophores, which constituted parts of the polymer backbones. 4–7 were soluble in polar solvents such as acetone and N,N‐dimethylformamide. They showed thermal stability up to 300 °C in thermogravimetric analysis thermograms; the glass‐transition temperatures obtained from differential scanning calorimetry thermograms were around 153 °C. The second harmonic generation (SHG) coefficients (d33) of poled polymer films at the 1064‐cm−1 fundamental wavelength were around 4.35 × 10−9 esu. The dipole alignment exhibited exceptionally high thermal stability even at 45 °C higher than the glass‐transition temperature, and there was no SHG decay below 200 °C because of the partial main‐chain character of the polymer structure, which was acceptable for nonlinear optical device applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3189–3199, 2004
A first‐principles study on the magnetism of an Fe chain along the [110] direction on Cu(001)
Authors: Jin Ying Jiu , Kim In Gee , Lee Jae Il
Published: May 2004

Magnetic nanowires currently attract much attention due to possible applications in high‐density memory storage. The cover picture, taken from the Editor's Choice paper [1] of this issue, is the spin density contour plot for a Fe chain along the [110] direction on Cu(001) and shows a large eruption of the majority spins from the Fe atom site toward the vacuum region. The supported Fe chain exhibits a large enhanced magnetic moment of the Fe atom compared with that of bulk Fe.

The corresponding author, Jae Il Lee, is Professor at the Inha University, Incheon. His research group at the Department of Physics works on theoretical investigations of electronic structure and magnetism of materials using first‐principles energy band calculations.

This paper is a contribution from the International Symposium on Magnetic Materials and Applications and Winter Conference of the Korean Magnetics Society (2003 SOMMA/KMS Meeting), Daejeon, Korea, 3–6 December 2003. The proceedings of this conference are published in two parts in the present issue of phys. stat. sol. (b) and in phys. stat. sol. (a) 201, No. 8 (2004).
A generalized semantics of PROMELA for abstract model checking
Authors: Gallardo María del Mar , Merino Pedro , Pimentel Ernesto
Published: May 2004

Semantics of description languages for complex systems are a central issue for implementing verification methods such as
abstract model checking
. This technique is employed to verify systems by inspecting only a small state space that represents its potential behaviors. This paper presents a generalized operational semantics of the modelling language promela that provides the theoretical basis to introduce this promising method in the model checker SPIN. The generalization consists of identifying language aspects affected by the abstraction. Using these aspects as parameters, it is possible to obtain and relate different interpretations of the language. The new semantics provides a framework to reason about how to construct the tool αspin as an extension of spin.
Effects of alternative prey on predation by small mammals on gypsy moth pupae
Authors: Elkinton Joseph S. , Liebhold Andrew M. , Muzika Rose‐Marie
Published: May 2004

Previous work shows that predation by small mammals is a dominant cause of mortality of low‐density gypsy moths in North America and that declines in small mammal density result in increases in gypsy moth density. Here we examined whether predation by small mammals is density dependent by way of a type III functional response, and how predation is influenced by alternative prey. First we showed that the preference of predators for gypsy moth pupae was low compared to other experimental prey items, such as mealworm pupae and sunflower seeds. Predation on gypsy moth pupae was characterized by a type II functional response with percent predation highest at the lowest prey densities, whereas the functional response to sunflower seeds was characterized by a type III functional response in which predation increased with increasing prey density. These results suggest that predation by small mammals is unlikely to stabilize low‐density gypsy moth populations.
RACK1 inhibits the serum‐ and anchorage‐independent growth of v‐Src transformed cells
Authors: Mamidipudi Vidya , Chang Betty Y. , Harte Rachel A. , Lee Kelly C. , Cartwright Christine A.
Published: May 2004

Cancer cells are capable of serum‐ and anchorage‐independent growth, and focus formation on monolayers of normal cells. Previously, we showed that RACK1 inhibits c‐Src kinase activity and NIH3T3 cell growth. Here, we show that RACK1 partially inhibits v‐Src kinase activity, and the serum‐ and anchorage‐independent growth of v‐Src transformed cells, but has no effect on focus formation. RACK1‐overexpressing v‐Src cells show disassembly of podosomes, which are actin‐rich structures that are distinctive to fully transformed cells. Together, our results demonstrate that RACK1 overexpression in v‐Src cells partially reverses the transformed phenotype of the cells. Our results identify an endogenous inhibitor of the oncogenic Src tyrosine kinase and of cell transformation.
Arabidopsis homologues of the autophagy protein Atg8 are a novel family of microtubule binding proteins
Authors: Ketelaar Tijs , Voss Christiane , Dimmock Simon A. , Thumm Michael , Hussey Patrick J.
Published: May 2004

Autophagy is the non‐selective transport of proteins and superfluous organelles destined for degradation to the vacuole in fungae, or the lysosome in animal cells. Some of the genes encoding components of the autophagy pathway are conserved in plants, and here we show that Arabidopsis homologues of yeast Atg8 (Apg8/Aut7) and Atg4 (Apg4/Aut2) partially complement the yeast deletion strains. The yeast double mutant, a deletion strain with respect to both Atg8 and Atg4, could not be complemented by Arabidopsis Atg8, indicating that Arabidopsis Atg8 requires Atg4 for its function. Moreover, Arabidopsis Atg8 and Arabidopsis Atg4 interact directly in a two‐hybrid assay. Interestingly, Atg8 shows significant homology with the microtubule binding light chain 3 of MAP1A and B, and here we show that Arabidopsis Atg8 binds microtubules. Our results demonstrate that a principle component of the autophagic pathway in plants is similar to that in yeast and we suggest that microtubule binding plays a role in this process.
Peer Review: An Essential Step in the Publishing Process
Authors: Weil Jon
Published: May 2004

Among the many steps involved in publishing a professional paper, peer review of the submitted manuscript presents both a challenge and an opportunity. Peer review is essential to ensuring that published papers meet appropriate research, scholarship and journal criteria. Peer review is also a valuable resource, providing detailed, professional evaluations that help authors carry out and present scholarship of the highest quality. When combined with the commitment of the Journal of Genetic Counseling to encourage and mentor authors, it is also a resource for developing writing skills.
Benigne epilepsietypische Potentiale des Kindesalters (Rolando-Spikes) - neurobiologische und neuropsychologische Befunde und ihre klinische Bedeutung in der Kinder- und Jugendpsychiatrie
Authors: Holtmann M. , Becker K. , El-Faddagh M. , Schmidt M. H.
Published: May 2004

Zusammenfassung: Einleitung: Die Rolando-Epilepsie ist das häufigste Epilepsie-Syndrom im Kindesalter. Sie ist elektroenzephalographisch charakterisiert durch das Auftreten von fokalen epilepsietypischen Potentialen, den sog. Rolando-Spikes (benigne epilepsietypische Potentiale des Kindesalters, BEPK). BEPK treten mit einer Häufigkeit von etwa 1,5 bis 2,4% bei Kindern auf; nur ein Zehntel erleidet epileptische Anfälle. Methoden: Diese Arbeit gibt einen Überblick über genetische, epidemiologische, radiologische, neurophysiologische, metabolische und neuropsychologische Befunde bei Kindern mit BEPK. Resultate: Der epileptologische Verlauf ist günstig, eventuell auftretende Anfälle sistieren spätestens mit der Pubertät; die epilepsietypischen Potentiale sind dann nicht mehr nachweisbar. Entgegen früherer Annahmen erstreckt sich das Symptomenspektrum über seltene Anfälle hinaus auf neuropsychologische Beeinträchtigungen und Verhaltensauffälligkeiten, auch bei Kindern ohne manifeste Anfälle. Der Einfluss der Rolando-Spikes auf die Entwicklung betroffener Kinder und ihr Verhalten ist unklar. Durch zwei Modelle wird versucht, den Zusammenhang von paroxysmaler EEG-Aktivität und neuropsychologischen Auffälligkeiten zu erklären. Das erste betrachtet die beobachtbaren Defizite als vorübergehende kognitive Beeinträchtigung infolge der epileptischen Aktivität; das zweite sieht als Ursache eine genetisch bedingte zerebrale Reifungsstörung mit enger Verwandtschaft zu Teilleistungsstörungen. Schlussfolgerung: Die Behandlungsnotwendigkeit neuropsychiatrischer Symptome bei Kindern mit BEPK ohne manifeste Anfälle wird derzeit kontrovers diskutiert.
Der Einfluss von Temperament, Alkoholwirksamkeitserwartungen und Bezugsgruppe auf Trinkmenge und Alkoholprobleme im Jugendalter 1Die Arbeit ist Teil des Community-Medicine-Forschungsverbundes (CMF) der Universität Greifswald. Er wird gefördert von dem Bundesministerium für Bildung und Forschung (Förderkennzeichen ZZ9603), dem Kultusministerium und dem Sozialministerium des Landes Mecklenburg-Vorpommern. Der CMF umfasst mehrere Projekte, die Daten aus einer Basisstudie, der Study of Health in Pomerania analysieren (SHIP; www.medizin.uni-greifswald.de/cm).
Authors: Barnow S. , Schultz G. , Lucht M. , Ulrich I. , Freyberger H.-J.
Published: May 2004

Zusammenfassung: Fragestellung: In der vorliegenden Studie wurde untersucht, inwieweit Temperamentsmerkmale (Neugierverhalten, Schadensvermeidung und Belohnungsabhängigkeit), Alkoholwirksamkeitserwartungen und Devianz/Substanzgebrauch in der Peergroup einen Einfluss auf Alkoholprobleme und Trinkmenge im Jugendalter haben. Methode: 147 etwa 15-jährige Jugendliche wurden zu zwei Messzeitpunkten ausführlich befragt und erhielten darüber hinaus verschiedene Fragebögen. Ebenso wurden bei der ersten Erhebung die jeweiligen Elternteile interviewt. Ergebnisse: Jugendliche mit Alkoholproblemen zur Zeit der zweiten Befragung wiesen ein Jahr vorher im Vergleich zu Adoleszenten ohne Alkoholprobleme eine geringere Schadensvermeidung und Belohnungsabhängigkeit auf und waren häufiger Mitglied in einer devianten/substanzgebrauchenden Peergroup. Außerdem berichteten Jugendliche mit Alkoholproblemen signifikant mehr positive Alkoholwirksamkeitserwartungen. In Bezug auf die Trinkmenge konnten die Ergebnisse repliziert werden, wobei das Temperament aber kein bedeutsamer Prädiktor für die Trinkmenge pro Trinktag nach einem Jahr war. Schlussfolgerung: Alkoholwirksamkeitserwartungen und Devianz/Substanzgebrauch in der Peergroup zeigen bedeutsame Assoziationen sowohl mit der Trinkmenge pro Trinktag als auch der Entwicklung von Alkoholproblemen im Jugendalter und sollten deshalb Fokus von Präventions- und Interventionsmaßnahmen sein.
Effect of unbalanced topography and overloading on Coulomb wedge kinematics: Insights from sandbox modeling
Authors: Del Castello Mario , Pini Gian Andrea , McClay Kenneth R.
Published: May 2004

This study addresses the effect of variable unbalanced topography and overload on the kinematics of a fold and thrust belt developed within a collisional belt that underwent a subduction polarity reversal event. This was done by physical modeling of doubly vergent Coulomb wedges, using sand as an analogue material. During the experimental procedure a preexisting topography was generated by a first phase of subduction in one direction. A second phase of subduction was then initiated in the opposite direction (simulating a subduction flip). An anomalous, strong frontal growth for the wedge during the second phase was experimentally shown to be dependent upon surface slope breaks and the critical asymmetrical architecture achieved by the wedge at mature stages of deformation. The latter is suggested to be the rule for doubly vergent orogens at steady state, even after a subduction flip. During the experiments, surface processes, like syntectonic erosion and sedimentation, markedly altered mass transfer within the wedge. In particular, lowering the surface slope by syntectonic erosion favored cycling between accretion and underthrusting modes. By contrast, a sudden syntectonic sediment load in the prowedge region promoted prolonged phases of underthrusting, retarding accretion of new imbricates at the prowedge toe. However, at later stages of deformation the prowedge was forced to regain its characteristic minimum critical taper as predicted by theory and did so by the sudden nucleation of long, flat thrust units, rapidly rebalancing the asymmetry between prowedge and retrowedge regions. The experiments suggest that given a fixed critical taper related to time‐invariant frictional properties along the wedge bounding surfaces, deformation does vary within the wedge according to time‐varying location of normal stress surpluses and unbalanced topography acting on potential failure surfaces. These, in turn, alter the equilibrium between prowedge and retrowedge basal detachments that is here considered to be a major factor controlling the self‐regulating dynamics of collisional orogens.
The development of organized convection associated with the MJO during TOGA COARE IOP: Trimodal characteristics
Authors: Kikuchi Kazuyoshi , Takayabu Yukari N.
Published: May 2004

We constructed a composite lifecycle of the Madden‐Julian oscillation (MJO) with cloud‐top information and atmospheric temperature and moisture profiles. Japanese Geostationary Meteorological Satellite (GMS/IR TBB) histograms and upper‐soundings from the Tropical Ocean‐Global Atmosphere Coupled Ocean‐Atmosphere Response Experiment (TOGA COARE) intensive observation period (IOP) were analyzed around Ujung Pandang (119°E, 5°S) and Kupang (123°E, 10°S), which encountered the mature phase of MJO from January to February, 1993. Under a large‐scale boundary layer (BL) convergence, convection developed in stages:1) ‘suppressed stage’ with suppressed clouds, 2) ‘shallow convection stage’ (2–3 days) with clouds confined under the trade inversion level, 3) ‘developing stage’ (3–4 days) with most clouds stopped at the mid‐troposphere but some tall convective clouds developing 4) ‘mature stage’ (4–5 days) with large anvil cloud shields, and 5) ‘decaying stage’ with decaying anvils. These stages of MJO were related to three stable layers; trade inversion, 0°C level, and tropopause. It is suggested that staged convective development associated with the MJO was strongly affected by the interaction among convection, stable layers, and atmospheric moistening.
A Window on the Normal Development of Sensitivity to Global Form in Glass Patterns
Authors: Lewis Terri L , Ellemberg Dave , Maurer Daphne , Dirks Melanie , Wilkinson Fran , Wilson Hugh R
Published: May 2004

We studied the development of sensitivity to global form in 6-year-olds, 9-year-olds, and adults ( n = 24 in each group) using Glass patterns with varying ratios of paired signal dots to noise dots. The developmental pattern was similar whether the global structure within the Glass patterns was concentric or parallel. Thresholds were equally immature for both types of pattern at 6 years of age (about twice the adult value) but were adult-like at 9 years of age. Together, the results indicate that the cortical structures involved in the processing of global form achieve functional maturity between 6 and 9 years of age. During middle childhood, the mechanisms mediating sensitivity to concentric structure develop at the same rate as those mediating sensitivity to parallel structure.
Dynamers: Polyacylhydrazone reversible covalent polymers, component exchange, and constitutional diversity
Authors: Skene Williams G. , Lehn Jean-Marie P.
Published: May 2004

Component exchange in reversible polymers allows the generation of dynamic constitutional diversity. The polycondensation of dihydrazides with dialdehydes generates polyacylhydrazones, to which the acylhydrazone functionality formed confers both hydrogen-bonding and reversibility features through the amide and imine groups, respectively. Polyacylhydrazones are thus dynamic polyamides. They are able to reversibly exchange either one or both of their repeating monomer units in the presence of different monomers, thus presenting constitutional dynamic diversity. The polymers subjected to monomer exchange/interchange may be brought to exhibit physical properties vastly different from those of the original polymer. The principle may be extended to other important classes of polymers, giving access, for instance, to dynamic polyureas or polycarbamates. These reversible polymers are therefore able to incorporate, decorporate, or reshuffle their constituting monomers, namely in response to environmental physical or chemical factors, an adaptability feature central to constitutional dynamic chemistry.
The Fbw7 tumor suppressor regulates glycogen synthase kinase 3 phosphorylation-dependent c-Myc protein degradation
Authors: Welcker Markus , Orian Amir , Jin Jianping , Grim Jonathan A. , Harper J. Wade , Eisenman Robert N. , Clurman Bruce E.
Published: May 2004

Myc proteins regulate cell growth and division and are implicated in a wide range of human cancers. We show here that Fbw7, a component of the SCF
Fbw7
ubiquitin ligase and a tumor suppressor, promotes proteasome-dependent c-Myc turnover
in vivo
and c-Myc ubiquitination
in vitro
. Phosphorylation of c-Myc on threonine-58 (T58) by glycogen synthase kinase 3 regulates the binding of Fbw7 to c-Myc as well as Fbw7-mediated c-Myc degradation and ubiquitination. T58 is the most frequent site of c-
myc
mutations in lymphoma cells, and our findings suggest that c-Myc activation is one of the key oncogenic consequences of Fbw7 loss in cancer. Because Fbw7 mediates the degradation of cyclin E, Notch, and c-Jun, as well as c-Myc, the loss of Fbw7 is likely to elicit profound effects on cell proliferation during tumorigenesis.
Polarized delivery of viral glycoproteins to the apical and basolateral plasma membranes of Madin-Darby canine kidney cells infected with temperature-sensitive viruses.
Authors: Rindler M J , Ivanov I E , Plesken H , Sabatini D D
Published: May 2004

The intracellular route followed by viral envelope glycoproteins in polarized Madin-Darby canine kidney cells was studied by using temperature-sensitive mutants of vesicular stomatitis virus (VSV) and influenza, in which, at the nonpermissive temperature (39.5 degrees C), the newly synthesized glycoproteins (G proteins) and hemagglutinin (HA), respectively, are not transported out of the endoplasmic reticulum. After infection with VSV and incubation at 39.5 degrees C for 4-5 h, synchronous transfer of G protein to the plasma membrane was initiated by shifting to the permissive temperature (32.5 degrees C). Immunoelectron microscopy showed that under these conditions the protein moved to the Golgi apparatus and from there directly to a region of the lateral plasma membrane near this organelle. G protein then seemed to diffuse progressively to basal regions of the cell surface and, only after it had accumulated in the basolateral domain, it began to appear on the apical surface near the intercellular junctions. The results of these experiments indicate that the VSV G protein must be sorted before its arrival at the cell surface, and suggest that passage to the apical domain occurs only late in infection when tight junctions are no longer an effective barrier. In complementary experiments, using the temperature-sensitive mutant of influenza, cultures were first shifted from the nonpermissive temperature (39.5 degrees C) to 18.5 degrees C, to allow entrance of the glycoprotein into the Golgi apparatus (see Matlin, K.S., and K. Simons, 1983, Cell, 34:233-243). Under these conditions HA accumulated in Golgi stacks and vesicles but did not reach the plasma membrane. When the temperature was subsequently shifted to 32.5 degrees C, HA rapidly appeared in discrete regions of the apical surface near, and often directly above, the Golgi elements, and later diffused throughout this surface. To ensure that the anti-HA antibodies had access to lateral domains, monolayers were treated with a hypertonic medium to dilate the intercellular spaces. Some labeling was then observed in the lateral plasma membranes soon after the shift, but this never increased beyond 1.0 gold particle/micron, whereas characteristic densities of labeling in apical surfaces soon became much higher (approximately 10 particles/micron). Our results suggest that the bulk of HA follows a direct pathway leading from the Golgi to regions of the apical surface close to trans-Golgi cisternae.
Preferential outgrowth of central nervous system neurites on astrocytes and Schwann cells as compared with nonglial cells in vitro.
Authors: Fallon J R
Published: May 2004

I have compared central nervous system (CNS) neurite outgrowth on glial and nonglial cells. Monolayers of glial cells (astrocytes and Schwann cells) or nonglial cells (e.g., fibroblasts) were prepared and were shown to be greater than 95% pure as judged by cell type-specific markers. These monolayers were then tested for their ability to support neurite outgrowth from various CNS explants. While CNS neurites grew vigorously on the glial cells, most showed little growth on nonglial cell monolayers. Neurites grew singly or in fine fascicles on the glial cells at rates greater than 0.5 mm/d. The neurite outgrowth on astrocytes was investigated in detail. Scanning and transmission electron microscopy showed that the neurites were closely apposed to the astrocyte surface and that the growth cones were well spread with long filopodia. There was no evidence of significant numbers of explant-derived cells migrating onto the monolayers. Two types of experiments indicated that factors associated with the astrocyte surface were primarily responsible for the vigorous neurite outgrowth seen on these cells: (a) Conditioned media from either astrocytes or fibroblasts had no effect on the pattern of outgrowth on fibroblasts and astrocytes, and conditioned media factors from either cell type did not promote neurite outgrowth when bound to polylysine-coated dishes. (b) When growing CNS neurites encountered a boundary between astrocytes and fibroblasts, they stayed on the astrocytes and did not encroach onto the fibroblasts. These experiments strongly suggest that molecules specific to the surfaces of astrocytes make these cells particularly attractive substrates for CNS neurite outgrowth, and they raise the possibility that similar molecules on embryonic glial cells may play a role in guiding axonal growth during normal CNS development.
Purification and general properties of the DNA-binding protein (P16) from rat liver mitochondria.
Authors: Pavco P A , Van Tuyle G C
Published: May 2004

The mitochondrial DNA-binding protein P16 was isolated from rat liver mitochondrial lysates by affinity chromatography on single strand DNA agarose and separated from DNA in the preparation by alkaline CsCl isopycnic gradients. The top fraction of the gradients contained a single polypeptide species (Mr approximately equal to 15,200) based upon SDS PAGE. Digestion of single strand DNA-bound P16 with proteinase K produced a protease-insensitive, DNA-binding fragment (Mr approximately equal to 6,000) that has been purified by essentially the same procedures used for intact P16. The partial amino acid compositions for P16 and the DNA-binding fragment were obtained by conventional methods. Analysis of subcellular fractions revealed that nearly all of the cellular P16 was located in the mitochondria and that only trace amounts of protein of comparable electrophoretic mobility could be isolated from the nuclear or cytoplasmic fractions. The labeling of P16 with [35S]methionine in primary rat hepatocyte cultures was inhibited by more than 90% by the cytoplasmic translation inhibitor cycloheximide, but unaffected by the mitochondrial-specific agent chloramphenicol. These results indicate that P16 is synthesized on cytoplasmic ribosomes and imported into the mitochondria. The addition of purified P16 to deproteinized mitochondrial DNA resulted in the complete protection of the labeled nascent strands of displacement loops against branch migrational loss during cleavage of parental DNA with SstI, thus providing strong evidence that P16 is the single entity required for this in vitro function. Incubation of P16 with single strand phi X174 DNA, double strand (RF) phi X174 DNA, or Escherichia coli ribosomal RNA and subsequent analysis of the nucleic acid species for bound protein indicated a strong preference of P16 for single strand DNA and no detectable affinity for RNA or double strand DNA. Examination of P16-single strand phi X174 DNA complexes by direct electron microscopy revealed thickened, irregular fibers characteristic of protein-associated single strand DNA.
Intracellular translocation of fluorescent sphingolipids in cultured fibroblasts: endogenously synthesized sphingomyelin and glucocerebroside analogues pass through the Golgi apparatus en route to the plasma membrane.
Authors: Lipsky N G , Pagano R E
Published: May 2004

When monolayer cultures of Chinese hamster lung fibroblasts are briefly incubated at 2 degrees C with the fluorescent sphingolipid analogue, C6-NBD-ceramide (N- [7-(4-nitrobenzo-2-oxa-1,3-diazole)] aminocaproyl sphingosine), fluorescent labeling of the mitochondria, endoplasmic reticulum, and nuclear envelope occur. During further incubation at 37 degrees C, the Golgi apparatus, and later the plasma membrane, become intensely fluorescent. Within this period, the C6-NBD-ceramide is converted to equal amounts of fluorescent sphingomyelin and glucocerebroside (Lipsky, N. G., and R. E. Pagano, 1983, Proc. Natl. Acad. Sci. USA., 80:2608-2612). In the present study, the intracellular translocation of these metabolites and their subsequent appearance at the plasma membrane were investigated by fluorescence microscopy, the addition of the ionophore monensin, and the technique of "back exchange," in which the amounts and types of fluorescent lipids present at the cell surface are identified after their transfer from the cell surface into recipient vesicles. In control cells, the amount of fluorescent glucocerebroside and sphingomyelin that could be removed from the cell surface by back exchange increased during incubation at 37 degrees C, correlating with the increased fluorescence of the plasma membrane observed by microscopy. In the presence of 10 microM monensin, visible labeling of the plasma membrane was greatly diminished, whereas the Golgi apparatus became highly fluorescent and distended. The ability to remove fluorescent metabolites from the cell surface by back exchange was significantly but reversibly inhibited by monensin. Monensin also increased the total amount of fluorescent sphingomyelin, but not the glucocerebroside found in cells. Subcellular fractions were assayed for their ability to convert radiolabeled and fluorescent ceramides to the corresponding sphingomyelins and glucocerebrosides. The activities of parallel fractions coincided, suggesting that the presence of the NBD moiety did not affect the cellular metabolism of ceramide. Furthermore, the major peak of sphingomyelin- and glucocerebroside-synthesizing activity appeared to coincide with an enriched Golgi fraction. These results strongly suggest that fluorescent sphingomyelin was not synthesized at the plasma membrane as has recently been suggested for endogenous sphingomyelin. Rather, both the sphingomyelin and glucocerebroside analogues were synthesized intracellularly from C6-NBD-ceramide and translocated through the Golgi apparatus to the cell surface.
Identical distribution of fluorescently labeled brain and muscle actins in living cardiac fibroblasts and myocytes.
Authors: McKenna N , Meigs J B , Wang Y L
Published: May 2004

We have investigated whether living muscle and nonmuscle cells can discriminate between microinjected muscle and nonmuscle actins. Muscle actin purified from rabbit back and leg muscles and labeled with fluorescein isothiocyanate, and nonmuscle actin purified from lamb brain and labeled with lissamine rhodamine B sulfonyl chloride, were co-injected into chick embryonic cardiac myocytes and fibroblasts. When fluorescence images of the two actins were compared using filter sets selective for either fluorescein isothiocyanate or lissamine rhodamine B sulfonyl chloride, essentially identical patterns of distribution were detected in both muscle and nonmuscle cells. In particular, we found no structure that, at this level of resolution, shows preferential binding of muscle or nonmuscle actin. In fibroblasts, both actins are associated primarily with stress fibers and ruffles. In myocytes, both actins are localized in sarcomeres. In addition, the distribution of structures containing microinjected actins is similar to that of structure containing endogenous F-actin, as revealed by staining with fluorescent phalloidin or phallacidin. Our results suggest that, at least under these experimental conditions, actin-binding sites in muscle and nonmuscle cells do not discriminate among different forms of actins.
Adipocyte conversion of CHEF cells in serum-free medium.
Authors: Harrison J J , Soudry E , Sager R
Published: May 2004

When grown in the presence of serum with added insulin, Chinese hamster embryonic fibroblasts (CHEF/18) cells can be induced to become preadipocytes that are committed to the adipocyte pathway of terminal differentiation (Sager, R., and P. Kovac, 1982, Proc. Natl. Acad. Sci. USA, 79:480-484). We found that commitment to the adipocyte pathway, as well as terminal differentiation to form mature adipocytes, can occur in a defined serum-free medium containing insulin. When CHEF/18 cells are plated in serum-containing medium, only 5-10% of cells in each colony undergo terminal differentiation, whereas in serum-free medium, greater than 90% of the cells became adipocytes. These and other results show that CHEF/18 cells require no adipogenic factors in addition to insulin and the other components of the serum-free medium (transferrin, epithelial growth factor, thrombin) to form adipocytes, and furthermore, that serum inhibits the rate of terminal adipocyte differentiation of these cells. As little as 10 ng/ml insulin added to serum-containing medium can induce adipogenesis, suggesting that insulin rather than an insulinlike growth factor is the active agent. The results further demonstrate that virtually every CHEF/18 cell can be induced into the adipocyte pathway.
Developmentally regulated mRNAs in 3T3-adipocytes: analysis of transcriptional control.
Authors: Cook K S , Hunt C R , Spiegelman B M
Published: May 2004

We have investigated the regulation of mRNA synthesis during 3T3-adipocyte differentiation by measuring the transcription of specific genes in isolated preadipocyte and adipocyte nuclei. Transcription was assayed by hybridization of newly synthesized RNA to cDNA clones coding for glycerophosphate dehydrogenase (GPD), the induced protein of 13K which is shown here to be related to myelin protein P-2, the induced protein of 28K, actin, and two RNAs that are not developmentally regulated. Transcription of GPD and 13K was observed in adipocyte but not preadipocyte nuclei. Actin was transcribed in both types of nuclei but at a lower level in adipocytes. For most of the RNAs examined, there was a consistent relationship between amounts of nuclear transcription and the abundance of the corresponding cytoplasmic mRNA in adipocytes. However, 13K and 28K mRNAs are 10-100 times more abundant than would be predicted by their nuclear transcription alone. Preliminary mRNA turnover experiments in which 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole was used to inhibit mRNA synthesis suggest that these mRNAs are much more stable in the adipocyte cytoplasm than the other mRNAs examined. These results indicate that the transcription of specific genes is increased during adipocyte differentiation and suggest that other levels of control, particularly mRNA stability, may contribute to the relative abundance of certain developmentally-regulated mRNAs in adipocytes.
The acrosomal membrane of boar sperm: a Golgi-derived membrane poor in glycoconjugates.
Authors: Aguas A P , Pinto da Silva P
Published: May 2004

The acrosome is a large secretory vesicle of the sperm head that carries enzymes responsible for the digestion of the oocyte's investments. The event leads to sperm penetration and allows fertilization to occur. Release of the acrosomal enzymes is mediated by the interaction between sperm acrosomal and plasma membranes (acrosome reaction). Biochemical characterization of the acrosomal membrane has been restrained by a lack of methods to isolate uncontaminated fractions of the membrane. Here, we use new methods to expose the membrane to in situ cytochemical labeling by lectin-gold complexes. We study the topology and relative density of glycoconjugates both across and along the plane of the acrosomal membrane of boar sperm. Detachment of the plasma membrane from glutaraldehyde-fixed cells exposed the cytoplasmic surface of the acrosome to the lectin markers; freeze-fractured halves of the acrosomal membrane were marked by "fracture-label" (Aguas, A. P., and P. Pinto da Silva, 1983, J. Cell Biol. 97:1356-1364). We show that the cytoplasmic surface of the intact acrosome is devoid of binding sites for both concanavalin A (Con A) and wheat germ agglutinin (WGA). By contrast, it contains a high density of neuraminidase-resistant anionic sites detected by cationic ferritin. On freeze-fractured sperm, the receptors for Con A partitioned with the exoplasmic membrane half of the acrosomal membrane. The Con A-binding glycoconjugates were accumulated on the equatorial segment of the membrane. A low density of WGA receptors, as well as of intramembrane particles, was found on the freeze-fracture halves of the acrosomal membrane. The plasma membrane displayed, in the same preparations, a high density of receptors for both Con A and WGA. We conclude that the acrosome is limited by a membrane poor in glycoconjugates, which are exclusively exposed on the exoplasmic side of the bilayer. Regionalization of Con A receptors on the acrosome shows that sperm intracellular membranes, like the sperm surface, express domain distribution of glycocomponents.
Localization of ribosomal protein S1 in the granular component of the interphase nucleolus and its distribution during mitosis.
Authors: Hügle B , Hazan R , Scheer U , Franke W W
Published: May 2004

Using antibodies to various nucleolar and ribosomal proteins, we define, by immunolocalization in situ, the distribution of nucleolar proteins in the different morphological nucleolar subcompartments. In the present study we describe the nucleolar localization of a specific ribosomal protein (S1) by immunofluorescence and immunoelectron microscopy using a monoclonal antibody (RS1-105). In immunoblotting experiments, this antibody reacts specifically with the largest and most acidic protein of the small ribosomal subunit (S1) and shows wide interspecies cross-reactivity from amphibia to man. Beside its localization in cytoplasmic ribosomes, this protein is found to be specifically localized in the granular component of the nucleolus and in distinct granular aggregates scattered over the nucleoplasm. This indicates that ribosomal protein S1, in contrast to reports on other ribosomal proteins, is not bound to nascent pre-rRNA transcripts but attaches to preribosomes at later stages of rRNA processing and maturation. This protein is not detected in the residual nucleolar structures of cells inactive in rRNA synthesis such as amphibian and avian erythrocytes. During mitosis, the nucleolar material containing ribosomal protein S1 undergoes a remarkable transition and shows a distribution distinct from that of several other nucleolar proteins. In prophase, the nucleolus disintegrates and protein S1 appears in numerous small granules scattered throughout the prophase nucleus. During metaphase and anaphase, a considerable amount of this protein is found in association with the surfaces of all chromosomes and finely dispersed in the cell plasm. In telophase, protein S1-containing material reaccumulates in granular particles in the nucleoplasm of the newly formed nuclei and, finally, in the re-forming nucleoli. These observations indicate that the nucleolus-derived particles containing ribosomal protein S1 are different from cytoplasmic ribosomes and, in the living cell, are selectively recollected after mitosis into the newly formed nuclei and translocated into a specific nucleolar subcompartment, i.e., the granular component. The nucleolar location of ribosomal protein S1 and its rearrangement during mitosis is discussed in relation to the distribution of other nucleolar proteins.
Cytosolic free calcium-ion concentration in cleaving embryonic cells of Oryzias latipes measured with calcium-selective microelectrodes.
Authors: Schantz A R
Published: May 2004

Calcium-selective microelectrodes were used to measure the free calcium-ion concentration ([Ca2+]i) in early-cleaving embryonic cells of the golden medaka, Oryzias latipes, a fresh water teleost fish. Embryos could be dechorionated as early as the four-cell stage using a three-step technique consisting of removal of some yolk to enlarge the perivitelline space, partial digestion of the chorion with pancreatin, and removal of the weakened chorion with forceps. Dechorionated embryos underwent cleavage at a normal rate. Intracellular cytosolic [Ca2+]i was monitored by impaling blastomeres first with a microelectrode filled with 5 M potassium acetate to measure membrane potential, and a few minutes later with a calcium-selective microelectrode. During nine rounds of cytokinesis from a total of six different embryos, cytosolic [Ca2+]i remained constant (with apparently random fluctuations of less than +/- 0.1 microM). During two successive cleavages in one embryo, however, [Ca2+]i rose transiently fourfold above the original resting level to 1.32 and 1.20 microM in synchrony with each period of cytokinesis and returned after each rise to submicromolar levels. Because a calcium-selective microelectrode can detect [Ca2+]i changes only in the immediate vicinity of its 2-microns tip, we interpreted these data to suggest that, although [Ca2+]i in most areas of the cytosol remains between 0.01 and 0.40 microM (mean of 0.14 microM), there may be small regions of the cell in which [Ca2+]i undergoes a substantial increase at the time of cleavage. Evidence also is presented to suggest that the membrane potential in these blastomeres undergoes a slow net hyperpolarization during early cleavage stages.
Defective temporal and spatial control of flagellar assembly in a mutant of Chlamydomonas reinhardtii with variable flagellar number.
Authors: Adams G M , Wright R L , Jarvik J W
Published: May 2004

Wild-type Chlamydomonas reinhardtii carry two flagella per cell that are used for both motility and mating. We describe a mutant, vfl-1, in which the biflagellate state is disrupted such that the number of flagella per cell ranges from 0 to as many as 10. vfl-1 cells possess the novel ability to assemble new flagella throughout the G1 portion of the cell cycle, resulting in an average increase of about 0.05 flagella per cell per hour. Such uncoupling of the flagellar assembly cycle from the cell cycle is not observed in other mutants with abnormal flagellar number. Rather than being located in an exclusively apical position characteristic of the wild type, vfl-1 flagella can be at virtually any location on the cell surface. vfl-1 cells display abnormally wide variations in cell size, probably owing to extremely unequal cell divisions. Various ultrastructural abnormalities in the flagellar apparatus are also present, including missing or defective striated fibers and reduced numbers of rootlet microtubules. The pleiotropic defects observed in vfl-1 result from a recessive Mendelian mutation mapped to Chromosome VIII.