bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of the α6β4 Integrin in Keratinocytes
Authors: Geuijen Cecile A. W. , Sonnenberg Arnoud
Published: November 2002

The integrin α6β4 has been implicated in two apparently contrasting processes, i.e., the formation of stable adhesions, and cell migration and invasion. To study the dynamic properties of α6β4 in live cells two different β4-chimeras were stably expressed in β4-deficient PA-JEB keratinocytes. One chimera consisted of full-length β4 fused to EGFP at its carboxy terminus (β4-EGFP). In a second chimera the extracellular part of β4 was replaced by EGFP (EGFP-β4), thereby rendering it incapable of associating with α6 and thus of binding to laminin-5. Both chimeras induce the formation of hemidesmosome-like structures, which contain plectin and often also BP180 and BP230. During cell migration and division, the β4-EGFP and EGFP-β4 hemidesmosomes disappear, and a proportion of the β4-EGFP, but not of the EGFP-β4 molecules, become part of retraction fibers, which are occasionally ripped from the cell membrane, thereby leaving “footprints” of the migrating cell. PA-JEB cells expressing β4-EGFP migrate considerably more slowly than those that express EGFP-β4. Studies with a β4-EGFP mutant that is unable to interact with plectin and thus with the cytoskeleton (β4R1281W-EGFP) suggest that the stabilization of the interaction between α6β4 and LN-5, rather than the increased adhesion to LN-5, is responsible for the inhibition of migration. Consistent with this, photobleaching and recovery experiments revealed that the interaction of β4 with plectin renders the bond between α6β4 and laminin-5 more stable, i.e., β4-EGFP is less dynamic than β4R1281W-EGFP. On the other hand, when α6β4 is bound to laminin-5, the binding dynamics of β4 to plectin are increased, i.e., β4-EGFP is more dynamic than EGFP-β4. We suggest that the stability of the interaction between α6β4 and laminin-5 is influenced by the clustering of α6β4 through the deposition of laminin-5 underneath the cells. This clustering ultimately determines whether α6β4 will inhibit cell migration or not.
Phospholipase D2 Is Localized to the Rims of the Golgi Apparatus in Mammalian Cells
Authors: Freyberg Zachary , Bourgoin Sylvain , Shields Dennis
Published: November 2002

Phospholipase D (PLD) hydrolyzes phosphatidylcholine to generate phosphatidic acid, a molecule known to have multiple physiological roles, including release of nascent secretory vesicles from thetrans-Golgi network. In mammalian cells two forms of the enzyme, PLD1 and PLD2, have been described. We recently demonstrated that PLD1 is localized to the Golgi apparatus, nuclei, and to a lesser extent, plasma membrane. Due to its low abundance, the intracellular localization of PLD2 has been characterized only indirectly through overexpression of chimeric proteins. Using antibodies specific to PLD2, together with immunofluorescence microscopy, herein we demonstrate that a significant fraction of endogenous PLD2 localized to the perinuclear Golgi region and was also distributed throughout cells in dense cytoplasmic puncta; a fraction of which colocalized with caveolin-1 and the plasma membrane. On treatment with brefeldin A, PLD2 translocated into the nucleus in a manner similar to PLD1, suggesting a potential role in nuclear signaling. Most significantly, cryoimmunogold electron microscopy demonstrated that in pituitary GH3cells >90% of PLD2 present in the Golgi apparatus was localized to cisternal rims and peri-Golgi vesicles exclusively. The data are consistent with a model whereby PLD2 plays a role in Golgi vesicular transport.
THE EQUIVALENCE PROBLEM IN TELEPARALLEL GRAVITY
Authors: FONSECA J.
Published: November 2002

The teleparallel equivalent of general relativity (TEGR) is an alternative formulation of Einstein's equations in the framework of Riemann-Cartan spacetimes. The gravitational field can be described either by the curvature of the torsion-free connection of general relativity (GR) or by the torsion of the curvature-free connection of the TEGR. Both in GR and TEGR the freedom in the choice of coordinates gives rise to the equivalence problem of deciding whether two solutions of the field equations are the same. This problem is solved by means of a invariant description of the gravitational field. We investigate whether the equivalence between GR and TEGR also holds at the level of these invariant descriptions. We show that the GR description assures equivalence in TEGR only in very special situations. These results are illustrated on teleparallel spacetimes with torsion and Gödel metric.
QUINTESSENCE TRACKING IN GENERALISED SETTINGS
Authors: HUEY GREG , TAVAKOL REZA
Published: November 2002

Quintessence tracking models have been put forward as a way of providing the missing cosmic energy required to make up for the shortfall between the observed clumped matter density and the critical density - as seems to be demanded by current observations - as well as simultaneously solving the initial condition problem faced by a cosmological constant. The robustness of this tracking quintessence scenario has recently been studied in more general cosmologies inspired by high-energy physics - cosmologies that include multiple scalar fields, brane corrections to the Hubble expansion law as well as potentials that decay with expansion. Here we give a summary of these results and apply them to the concrete case of a model with two scalar fields.
Meiotic Recombination and Chromosome Segregation in Drosophila Females
Authors: McKim Kim S. , Jang Janet K. , Manheim Elizabeth A.
Published: November 2002

▪ Abstract  In this review, we describe the pathway for generating meiotic crossovers in Drosophila melanogaster females and how these events ensure the segregation of homologous chromosomes. As appears to be common to meiosis in most organisms, recombination is initiated with a double-strand break (DSB). The interesting differences between organisms appear to be associated with what chromosomal events are required for DSBs to form. In Drosophila females, the synaptonemal complex is required for most DSB formation. The repair of these breaks requires several DSB repair genes, some of which are meiosis-specific, and defects at this stage can have effects downstream on oocyte development. This has been suggested to result from a checkpoint-like signaling between the oocyte nucleus and gene products regulating oogenesis. Crossovers result from genetically controlled modifications to the DSB repair pathway. Finally, segregation of chromosomes joined by a chiasma requires a bipolar spindle. At least two kinesin motor proteins are required for the assembly of this bipolar spindle, and while the meiotic spindle lacks traditional centrosomes, some centrosome components are found at the spindle poles.
Xist RNA and the Mechanism of X Chromosome Inactivation
Authors: Plath Kathrin , Mlynarczyk-Evans Susanna , Nusinow Dmitri A. , Panning Barbara
Published: November 2002

▪ Abstract  Dosage compensation in mammals is achieved by the transcriptional inactivation of one X chromosome in female cells. From the time X chromosome inactivation was initially described, it was clear that several mechanisms must be precisely integrated to achieve correct regulation of this complex process. X-inactivation appears to be triggered upon differentiation, suggesting its regulation by developmental cues. Whereas any number of X chromosomes greater than one is silenced, only one X chromosome remains active. Silencing on the inactive X chromosome coincides with the acquisition of a multitude of chromatin modifications, resulting in the formation of extraordinarily stable facultative heterochromatin that is faithfully propagated through subsequent cell divisions. The integration of all these processes requires a region of the X chromosome known as the X-inactivation center, which contains the Xist gene and its cis-regulatory elements. Xist encodes an RNA molecule that plays critical roles in the choice of which X chromosome remains active, and in the initial spread and establishment of silencing on the inactive X chromosome. We are now on the threshold of discovering the factors that regulate and interact with Xist to control X-inactivation, and closer to an understanding of the molecular mechanisms that underlie this complex process.
Estimating F-Statistics
Authors: Weir B. S. , Hill W. G.
Published: November 2002

▪ Abstract  A moment estimator of θ, the coancestry coefficient for alleles within a population, was described by Weir & Cockerham in 1984 ( 100 ) and is still widely cited. The estimate is used by population geneticists to characterize population structure, by ecologists to estimate migration rates, by animal breeders to describe genetic variation, and by forensic scientists to quantify the strength of matching DNA profiles. This review extends the work of Weir & Cockerham by allowing different levels of coancestry for different populations, and by allowing non-zero coancestries between pairs of populations. All estimates are relative to the average value of θ between pairs of populations. Moment estimates for within- and between-population θ values are likely to have large sampling variances, although these may be reduced by combining information over loci. Variances also decrease with the numbers of alleles at a locus, and with the numbers of populations sampled. This review also extends the work of Weir & Cockerham by employing maximum likelihood methods under the assumption that allele frequencies follow the normal distribution over populations. For the case of equal θ values within populations and zero θ values between populations, the maximum likelihood estimate is the same as that given by Robertson & Hill in 1984 ( 70 ). The review concludes by relating functions of θ values to times of population divergence under a pure drift model.
Clinical benefit of joint distraction in the treatment of severe osteoarthritis of the ankle: Proof of concept in an open prospective study and in a randomized controlled study
Authors: Marijnissen Anne C. A. , Van Roermund Peter M. , Van Melkebeek Jan , Schenk Willem , Verbout Abraham J. , Bijlsma Johannes W. J. , Lafeber Floris P. J. G.
Published: November 2002

Objective

Osteoarthritis (OA) is a degenerative, disabling joint disease that affects >10% of the adult population. No effective disease‐modifying treatment is available. In the present study, we used joint distraction, a relatively new treatment in which mechanical contact between the articular surfaces is avoided while intraarticular intermittent fluid pressure is maintained, to treat patients with severe OA of the ankle.

Methods

Patients with severe ankle OA (n = 57) who were being considered for joint fusion (arthrodesis) were treated with joint distraction in an open prospective study. In addition, a randomized trial was performed in 17 patients to determine whether joint distraction had a better outcome than debridement. A standardized evaluation protocol (physical examination, assessment of pain, mobility, and functional ability) was used, and changes in radiographic joint space width and subchondral sclerosis were measured. Thirty‐eight patients in the open study have been followed up for >1 year, with up to 5 years of followup in 7 of them (mean ± SD followup 2.8 ± 0.3 years). Patients in the randomized study have been followed up for 1 year.

Results

Significant clinical benefit was found in three‐fourths of the 57 patients in the open prospective study. Most interestingly, the improvement increased over time. Radiographic evaluation showed increased joint space width and decreased subchondral sclerosis. Moreover, joint distraction showed significantly better results than debridement.

Conclusion

The clinical benefit of joint distraction in the treatment of severe OA is proof of the concept. Although the followup remains relatively short and effects over time remain unpredictable, our study creates possibilities for the treatment of severe OA in general. Considering the high prevalence of OA and the lack of a cure for it, joint distraction as a treatment of severe OA may have great medical, social, and economic impact.
Transforming growth factor β induces fibroblast fibrillin‐1 matrix formation
Authors: Kissin Eugene Y. , Lemaire Raphael , Korn Joseph H. , Lafyatis Robert
Published: November 2002

Objective

Fibrillin, an extracellular matrix protein implicated in dermal fibrosis, is increased in the reticular dermis of systemic sclerosis (SSc) skin. We undertook this study to investigate the hypothesis that transforming growth factor β (TGFβ) or other cytokines regulate fibrillin matrix formation by normal and SSc fibroblasts. We further investigated the mechanism of TGFβ‐induced fibrillin fibrillogenesis and its relationship to myofibroblasts.

Methods

Fibrillin and fibronectin matrix deposition and α‐smooth muscle actin expression by fibroblast cultures from normal and SSc skin treated with TGFβ or other cytokines were analyzed by immunofluorescence. Supernatant and extracellular matrix from normal and SSc fibroblasts treated with or without TGFβ were evaluated by Western blot and Northern blot for fibrillin protein and messenger RNA (mRNA) expression, respectively.

Results

Immunofluorescence demonstrated increased fibrillin matrix formation by normal and scleroderma fibroblasts after TGFβ treatment. Other cytokines, including tumor necrosis factor α, interleukin‐1β (IL‐1β), IL‐4, granulocyte–macrophage colony‐stimulating factor, and platelet‐derived growth factor, did not affect fibrillin fibrillogenesis. Fibrillin matrix formed in proximity to myofibroblasts and independently of up‐regulation of fibronectin matrix or cell number. Western blot analysis of extracellular matrix confirmed increased fibrillin after TGFβ stimulation of normal or scleroderma fibroblasts. However, TGFβ did not alter the expression of either soluble fibrillin protein or fibrillin mRNA.

Conclusion

Our data show that TGFβ induces fibrillin protein incorporation into the extracellular matrix without affecting fibrillin gene expression or protein synthesis, suggesting that fibrillin matrix assembly is regulated extracellularly. TGFβ might increase fibrillin matrix by activating myofibroblasts. Such TGFβ‐mediated effects could account for the increased fibrillin matrix observed in SSc skin.
Determining the molecular weight, aggregation, structures and interactions of natural organic matter using diffusion ordered spectroscopy
Authors: Simpson André J.
Published: November 2002

Diffusion ordered spectroscopy (DOSY) was applied to examine the chemical and physical properties of soil organic matter, a complex natural mixture. Soil organic matter extracts are often termed humic substances (HS), which traditionally have been thought to be high molecular weight, cross‐linked macromolecules with undetermined structures. Separation of the components in the studied humic acid (HA) clearly indicates that the HS studied here are pseudo‐high molecular weight materials only, and associations or aggregates of molecules of smaller molecular sizes, which can be disrupted with organic acids. At high concentration, these aggregates display diffusivities that are consistent with those observed in large proteins (>66 kDa). After disaggregation and at low concentration, DOSY NMR reveals components that have chemical shifts that are consistent with lignins, polysaccharides and peptides, and have diffusivities consistent with molecular weights of ∼2500, ∼1000 and 200–600 Da, respectively. Diffusion studies of fulvic acids (FA) indicate that little if any aggregation occurs in solution and that, on average, the components display diffusivities that are consistent with molecules that have relatively low molecular weights of ∼1000 Da. However, in addition to a range of small molecular components, DOSY NMR reveals for the first time direct evidence that larger molecular weight components also exist within the mixtures. In an FA isolated from the surface soil of an oak forest, large polysaccharides with average diffusivities similar to 6000 Da maltodextrins can be identified. In an FA from an agricultural soil, components consistent with peptides/proteins are identified that have aggregate/molecular sizes in the region of 12 000 Da. It is logical that an operationally defined extract of soils will result in a mixture of plant components at various stages of humification with a range of molecular sizes and structures rather than macromolecules with undetermined structures. In addition to advancing our structural understanding of natural organic matter (NOM), DOSY provides potential to study the interactions of these mixtures with contaminants. This paper explorers the interaction of a HA with two organic contaminants (MTBE and chlorsulfuron) and an FA with cadmium. Diffusion measurements show that MTBE has a weaker interaction with the organic materials than chlorsulfuron. Studies with cadmium suggest that the metal exhibits dynamic exchange which is fast on the NMR time‐scale. Such findings have strong implications for understanding the behavior and toxicity of cadmium in the environment. Although cadmium has an affinity for NOM, it is clear that it is not irreversibly bound and may be bioavailable under many conditions. Copyright © 2002 John Wiley & Sons, Ltd.
Monitoring the non‐specific interactions of catechin through diffusion measurements based on pulsed‐field gradients
Authors: Monteiro C. , Maechling C. , Hervé du Penhoat C.
Published: November 2002

The self‐association of aqueous catechin as a function of concentration was monitored through variations in 1H chemical shifts, proton T1 and T2 data and translational diffusion coefficients obtained with the pulsed‐field gradient spin‐echo method. The latter approach is very efficient and it is not restricted to aromatic compounds. Equilibrium constants were estimated for various models of self‐association and the apparent enthalpy of dissociation was measured with isothermal titration calorimetry. Comparison of the latter parameter with thermodynamic data reported for various types of non‐specific interactions suggests that such phenomena could be studied using this approach. Copyright © 2002 John Wiley & Sons, Ltd.
PGSE NMR diffusion study of the self‐association of N‐methylacetamide in carbon tetrachloride
Authors: Regan David G. , Chapman Bogdan E. , Kuchel Philip W.
Published: November 2002

N‐Methylacetamide (NMA) is known to self‐associate in solution through the formation of hydrogen bonds. This behavior, and the presence in the molecule of an amide bond, make this an interesting model for study since the oligomer can be considered to be a protein analogue. The aims of the present study were to estimate the thermodynamic parameters of the self‐association process, through the measurement of the diffusion coefficient of NMA in carbon tetrachloride (CCl4), and to predict the population distribution of oligomers as a function of the concentration of NMA. Diffusion coefficients were measured using pulsed field gradient spin‐echo (PGSE) NMR spectroscopy. A computer model based on the Kirkwood–Riseman theory of macromolecular diffusion and an attenuative model of self‐association were used to fit the experimental data and to derive estimates of the thermodynamic association constants and bond length, and these values were, in turn, used to estimate the oligomer distribution. In addition, the temperature dependence of the diffusion coefficient was measured at three different concentrations in order to calculate the apparent Arrhenius activation energies so as to provide additional insight into the self‐association process. Finally, the concentration dependence of the viscosity of NMA in CCl4 was measured to characterize further the hydrodynamic behavior of the polydisperse system. Copyright © 2002 John Wiley & Sons, Ltd.
The steady propagation of a semi-infinite bubble
into a tube of elliptical or rectangular
cross-section
Authors: HAZEL ANDREW L. , HEIL MATTHIAS
Published: November 2002

This paper investigates the propagation of an air finger into a fluid-filled, axially
uniform tube of elliptical or rectangular cross-section with transverse length scale a
and aspect ratio α. Gravity is assumed to act parallel to the tube's axis. The problem
is studied numerically by a finite-element-based direct solution of the free-surface
Stokes equations.

In rectangular tubes, our results for the pressure drop across the bubble tip, Δp,
are in good agreement with the asymptotic predictions of Wong et al. (1995b) at
low values of the capillary number, Ca (ratio of viscous to surface-tension forces).
At larger Ca, Wong et al.'s (1995b) predictions are found to underestimate Δp. In
both elliptical and rectangular tubes, the ratio Δp(α)/Δp(α = 1) is approximately
independent of Ca and thus equal to the ratio of the static meniscus curvatures.

In non-axisymmetric tubes, the air-liquid interface develops a noticeable asymmetry
near the bubble tip at all values of the capillary number. The tip asymmetry decays
with increasing distance from the bubble tip, but the decay rate becomes very small
as Ca increases. For example, in a rectangular tube with α = 1.5, when Ca = 10, the
maximum and minimum finger radii still differ by more than 10% at a distance 100a
behind the finger tip. At large Ca the air finger ultimately becomes axisymmetric with
radius r∞. In this regime, we find that r∞ in elliptical and rectangular tubes is related
to r∞ in circular and square tubes, respectively, by a simple, empirical scaling law. The scaling has the physical interpretation that for rectangular and elliptical tubes of
a given cross-sectional area, the propagation speed of an air finger, which is driven by
the injection of air at a constant volumetric rate, is independent of the tube's aspect
ratio.

For smaller Ca (Ca <
Ca), the air finger is always non-axisymmetric and the
persisting draining flows in the thin film regions far behind the bubble tip ultimately
lead to dry regions on the tube wall.
Ca increases with increasing α and for α > αˆ
dry spots will develop on the tube walls at all values of Ca.
Cell allocation in bovine embryos cultured in two media under two oxygen concentrations
Authors: Fischer-Brown Amy , Monson Rick , Parrish John , Rutledge Jack
Published: November 2002

Blastocyst development, total cell number and allocation to inner cell mass (ICM) and trophectoderm (TE) lineages was compared among day 9 hatched blastocysts from four culture treatments in a two-factor design. Two modified commercial media (KSOM and SOF) were used in atmospheres with two oxygen concentrations (5% and 20% O2). No significant effect of medium on development was found, but 20% O2 increased hatching (p < 0.05). There were more cells in hatched blastocysts cultured in KSOM than in SOF (181 vs 136, respectively; p < 0.0001); however, ICM/total cell ratio was not affected by medium. There was a trend suggesting that the proportion of cells allocated to ICM was lower in hatched blastocysts cultured under 5% O2 compared with 20% O2 (0.323 vs 0.380, respectively; p < 0.1). No significant interactions between medium type and oxygen concentration were found. These results indicate that culture components used in this study may affect cell proliferation without altering cell allocation, and that oxygen concentration may play a role in allocation of cells to ICM and TE lineages.
Research and the realities of the industry
Authors: Stansfield Smith Colin
Published: November 2002

As a former student of Leslie Martin
I well understand that ‘in the UK,
architecture's standing as a
research-led University discipline
remains as low as ever’ (arq 5/4,
p291). But then I share my own
generation's disbelief about the
current state of the Profession and
the failure of any architecture
school to be awarded the highest
rating (5*)in the latest Research
Assessment Exercise (RAE). The
internecine misunderstandings
between practice and schools of
architecture are hardly helpful to
the cause: the Profession's refusal to
understand the current plight of
schools with regard to resources
and the low esteem and status of
academic staff and – in the reverse
perspective – academia seems
oblivious to the cowed posture of
large sections of the Profession in a
world driven by the imperatives of
the government's Private Finance
Initiative (PFI). This more or less
symbolizes in a general sense the
current client/architect
relationship or lack of it in the
public realm.
The RIBA: action at last?
Authors: Jones Alan
Published: November 2002

I received a copy of your letter
inviting a response to the issues
regarding research and its
relationship with practising and
teaching architecture.
Effects of non‐steroidal anti‐inflammatory drugs on cyclo‐oxygenase and lipoxygenase activity in whole blood from aspirin‐sensitive asthmatics vs healthy donors
Authors: Gray P A , Warner T D , Vojnovic I , Del Soldato P , Parikh A , Scadding G K , Mitchell J A
Published: November 2002

Cyclo‐oxygenase (COX) and lipoxygenase (LO) share a common substrate, arachidonic acid. Aspirin and related drugs inhibit COX activity. In a subset of patients with asthma aspirin induces clinical symptoms associated with increased levels of certain LO products, a phenomenon known as aspirin‐sensitive asthma. The pharmacological pathways regulating such responses are not known.

Here COX‐1 and LO activity were measured respectively by the formation of thromboxane B2 (TXB2) or leukotrienes (LT) C4, D4 and E4 in whole blood stimulated with A23187. COX‐2 activity was measured by the formation of prostaglandin E2 (PGE2) in blood stimulated with lipopolysaccharide (LPS) for 18 h.

No differences in the levels of COX‐1, COX‐2 or LO products or the potency of drugs were found in blood from aspirin sensitive vs aspirin tolerant patients. Aspirin, indomethacin and nimesulide inhibited COX‐1 activity, without altering LO activity. Indomethacin, nimesulide and the COX‐2 selective inhibitor DFP [5,5‐dimethyl‐3‐(2‐isopropoxy)‐4‐(4‐methanesulfonylphenyl)‐2(5H)‐furanone] inhibited COX‐2 activity. NO‐aspirin, like aspirin inhibited COX‐1 activity in blood from both groups. However, NO‐aspirin also reduced LO activity in the blood from both patient groups. Sodium salicylate was an ineffective inhibitor of COX‐1, COX‐2 or LO activity in blood from both aspirin‐sensitive and tolerant patients.

Thus, when COX activity in the blood of aspirin‐sensitive asthmatics is blocked there is no associated increase in LO products. Moreover, NO‐aspirin, unlike other NSAIDs tested, inhibited LO activity in the blood from both aspirin sensitive and aspirin tolerant individuals. This suggests that NO‐aspirin may be better tolerated than aspirin by aspirin‐sensitive asthmatics.

British Journal of Pharmacology (2002) 137, 1031–1038. doi:10.1038/sj.bjp.0704927
Treatment Nonadherence: Causes and Potential Solutions
Authors: Jarboe Kathleen S.
Published: November 2002

When patients are nonadherent to their antipsychotic therapy, their risk for relapse and disease exacerbation is greatly enhanced. These events may necessitate rehospitalization and may significantly increase the cost of care. Improving the propensity of patients to adhere to their regimen requires an assessment of patient attitudes and expectations concerning their medication and, if necessary, appropriate education. In addition, healthcare professionals need to foster therapeutic alliances by decreasing threats and avoiding the use of depot medications as a “punishment” for nonadherence. The type of medication may even influence the potential for improved adherence. Available data suggest that oral atypical antipsychotics offer the lowest potential for nonadherence and relapse, followed by depot conventional and oral conventional antipsychotics. The first long-acting atypical antipsychotic, an injectable preparation of risperidone, is anticipated soon. This drug will offer the efficacy and safety benefits of an atypical antipsychotic, with a much more stable pharmacokinetic profile than oral medication. Such medications may represent the next step in improving patient adherence to an antipsychotic regimen. Healthcare professionals need to understand that treatment nonadherence is human nature and not a result of mental illness. Only then can an effective and caring solution be implemented.
Evidence of hybridity in invasive watermilfoil (
Myriophyllum
) populations
Authors: Moody Michael L. , Les Donald H.
Published: November 2002

Invasions of nonindigenous species have caused ecological devastation to natural communities worldwide, yet the biological bases for invasiveness remain poorly understood. Our studies of invasive watermilfoil (
Myriophyllum
) populations revealed widespread polymorphisms in biparentally inherited nuclear ribosomal DNA sequences, which were not detected in populations of native North American species. Subclones of the polymorphic regions revealed the occurrence of distinct sequences matching those acquired from both nonindigenous and native North American species. Molecular data demonstrate clearly that invasive watermilfoil populations in North America have resulted from hybridization between nonindigenous and native species. These observations suggest that invasiveness in these aggressive aquatic weeds may be linked to heterosis maintained by vegetative propagation.
Origin of plant glycerol transporters by horizontal gene transfer and functional recruitment
Authors: Zardoya Rafael , Ding Xiaodong , Kitagawa Yoshichika , Chrispeels Maarten J.
Published: November 2002

Gene-family evolution mostly relies on gene duplication coupled with functional diversification of gene products. However, other evolutionary mechanisms may also be important in generating protein diversity. The ubiquitous membrane intrinsic protein (MIP) gene family is an excellent model system to search for such alternative evolutionary mechanisms. MIPs are proteins that transport water, glycerol, and small solutes across cell membranes in all living organisms. We reconstructed the molecular phylogeny of MIPs based on amino acid sequence data by using neighbor-joining, maximum-likelihood, and Bayesian methods of phylogenetic inference. The recovered trees show an early and distinct separation of water and glycerol transporters, i.e., aquaporins (AQPs), and aquaglyceroporins. The latter are absent from plants. As expected, gene duplication and functional diversification account for most of the diversity of animal and plant members of the family. However, in contrast to this model, we find that the sister group of plant glycerol transporters are bacterial AQPs. This relationship suggests first that plant glycerol transporters may resulted from a single event of horizontal gene transfer from bacteria, which we have estimated to have occurred ≈1,200 million years ago, at the origin of plants, and second that bacterial AQPs were likely recruited to transport glycerol in plants because of their absence of aquaglyceroporins. This striking example of adaptive evolution at the molecular level was demonstrated further by finding convergent or parallel replacements at particular amino acid positions related to water- and glycerol-transporting specificity.
Enhancing polyethylenimine's delivery of plasmid DNA into mammalian cells
Authors: Thomas Mini , Klibanov Alexander M.
Published: November 2002

The effect of various chemical modifications of nitrogen atoms on the efficiency of polyethylenimines (PEIs) as synthetic vectors for the delivery of plasmid DNA into monkey kidney cells
in vitro
has been systematically investigated. The resultant structure–activity relationship has both provided mechanistic insights and led to PEI derivatives with markedly enhanced performance. For example, N-acylation of PEI with the molecular mass of 25 kDa (PEI25, one of the most potent polycationic gene delivery vectors) with alanine nearly doubles its transfection efficiency in the presence of serum and also lowers its toxicity. Furthermore, dodecylation of primary amino groups of 2-kDa PEI yields a nontoxic polycation whose transfection efficiency in the presence of serum is 400 times higher than the parent's and which exceeds 5-fold even that of PEI25.
Transneuronal tracing of diverse CNS circuits by Cre-mediated induction of wheat germ agglutinin in transgenic mice
Authors: Braz Joao M. , Rico Beatriz , Basbaum Allan I.
Published: November 2002

Systems neuroscience addresses the complex circuits made by populations of neurons in the CNS and the cooperative function of these neurons. Improved approaches to the neuroanatomical analysis of CNS circuits are thus of great interest. In fact, significant advances in tract-tracing methods have recently been made by using transgenic mice that express transneuronal lectin tracers under the control of neuron-specific promoters. The utility of those animals, however, is limited to the CNS circuit influenced by the particular promoter. Here, we describe a new transgenic mouse that can be used for transneuronal tracing analysis of circuits in any region of the brain or spinal cord. The transgene in these mice results in expression of
LacZ
in neurons throughout the CNS. Excision of the
LacZ
gene by Cre-mediated recombination initiates expression of the lectin, wheat germ agglutinin (WGA). To illustrate the diverse uses of these ZW (
LacZ
-WGA) mice, we triggered WGA expression either by crossing the mice with two Cre-expressing transgenic mouse lines or by microinjecting a Cre-expressing adeno-associated virus into the cerebellum or cerebral cortex. Both approaches resulted in extensive WGA expression in the cell bodies and dendrites of neurons in which the recombination event occurred, as well as anterograde and transneuronal transport of the lectin to second and third order neurons. Because the lectin can be induced in developing and adult animals, and in all regions of the brain and spinal cord, these ZW may prove extremely valuable for numerous studies of CNS circuit analysis.
S-layer-streptavidin fusion proteins as template for nanopatterned molecular arrays
Authors: Moll Dieter , Huber Carina , Schlegel Birgit , Pum Dietmar , Sleytr Uwe B. , Sára Margit
Published: November 2002

Biomolecular self-assembly can be used as a powerful tool for nanoscale engineering. In this paper, we describe the development of building blocks for nanobiotechnology, which are based on the fusion of streptavidin to a crystalline bacterial cell surface layer (S-layer) protein with the inherent ability to self-assemble into a monomolecular protein lattice. The fusion proteins and streptavidin were produced independently in
Escherichia coli
, isolated, and mixed to refold and purify heterotetramers of 1:3 stoichiometry. Self-assembled chimeric S-layers could be formed in suspension, on liposomes, on silicon wafers, and on accessory cell wall polymer containing cell wall fragments. The two-dimensional protein crystals displayed streptavidin in defined repetitive spacing, and they were capable of binding
d
-biotin and biotinylated proteins. Therefore, the chimeric S-layer can be used as a self-assembling nanopatterned molecular affinity matrix to arrange biotinylated compounds on a surface. In addition, it has application potential as a functional coat of liposomes.
Transforming Growth Factor-β Receptors Interact with AP2 by Direct Binding to β2 Subunit
Authors: Yao Diying , Ehrlich Marcelo , Henis Yoav I. , Leof Edward B.
Published: November 2002

Transforming growth factor-β (TGF-β) superfamily members regulate a wide range of biological processes by binding to two transmembrane serine/threonine kinase receptors, type I and type II. We have previously shown that the internalization of these receptors is inhibited by K+depletion, cytosol acidification, or hypertonic medium, suggesting the involvement of clathrin-coated pits. However, the involvement of the clathrin-associated adaptor complex AP2 and the identity of the AP2 subunit that binds the receptors were not known. Herein, we have studied these issues by combining studies on intact cells with in vitro assays. Using fluorescence photobleaching recovery to measure the lateral mobility of the receptors on live cells (untreated or treated to alter their coated pit structure), we demonstrated that their mobility is restricted by interactions with coated pits. These interactions were transient and mediated through the receptors' cytoplasmic tails. To measure direct binding of the receptors to specific AP2 subunits, we used yeast two-hybrid screens and in vitro biochemical assays. In contrast to most other plasma membrane receptors that bind to AP2 via the μ2 subunit, AP2/TGF-β receptor binding was mediated by a direct interaction between the β2-adaptin N-terminal trunk domain and the cytoplasmic tails of the receptors; no binding was observed to the μ2, α, or ς2 subunits of AP2 or to μ1 of AP1. The data uniquely demonstrate both in vivo and in vitro the ability of β2-adaptin to directly couple TGF-β receptors to AP2 and to clathrin-coated pits, providing the first in vivo evidence for interactions of a transmembrane receptor with β2-adaptin.
Differential Regulation of Tumor Angiogenesis by Distinct ErbB Homo- and Heterodimers
Authors: Yen Lily , Benlimame Naciba , Nie Zeng-Rong , Xiao Dingzhang , Wang Taiqi , Moustafa Ala-Eddin Al , Esumi Hiroyasu , Milanini Julie , Hynes Nancy E. , Pages Gilles , Alaoui-Jamali Moulay A.
Published: November 2002

Interactions between cancer cells and their microenvironment are critical for the development and progression of solid tumors. This study is the first to examine the role of all members of the ErbB tyrosine kinase receptors (epidermal growth factor receptor [EGFR], ErbB-2, ErbB-3, or ErbB-4), expressed singly or as paired receptor combinations, in the regulation of angiogenesis both in vitro and in vivo. Comparison of all receptor combinations reveals that EGFR/ErbB-2 and ErbB-2/ErbB-3 heterodimers are the most potent inducers of vascular endothelial growth factor (VEGF) mRNA expression compared with EGFR/ErbB-3, EGFR/ErbB-4, ErbB-2/ErbB-4, and ErbB-3/ErbB-4. Immunohistochemistry of tumor xenografts overexpressing these heterodimers shows increased VEGF expression and remarkably enhanced vascularity. Enhanced VEGF expression is associated with increased VEGF transcription. Deletional analysis reveals that ErbB-mediated transcriptional up-regulation of VEGF involves a hypoxia-inducible factor 1-independent responsive region located between nucleotides −88 to −66 of the VEGF promoter. Mutational analysis reveals that the Sp-1 and AP-2 transcription factor binding elements within this region are required for up-regulation of VEGF by heregulin β1 and that this up-regulation is dependent on the activity of extracellular signal-related protein kinases. These results emphasize the biological implications of cell signaling diversity among members of the ErbB receptor family in regulation of the tumor microenvironment.
Stage-specific Requirement of a Mitogen-activated Protein Kinase byTrypanosoma brucei
Authors: Müller Ingrid B. , Domenicali-Pfister Debora , Roditi Isabel , Vassella Erik
Published: November 2002

In cycling between the mammalian host and the tsetse fly vector, African trypanosomes undergo adaptive differentiation steps that are coupled to growth control. The signaling pathways underlying these cellular processes are largely unknown. Mitogen-activated protein kinases (MAPKs) are known mediators of growth and differentiation in other eukaryotic organisms. To establish the function of a MAPK homologue, TbMAPK2, in T. brucei, a null mutant was constructed. Bloodstream forms of aΔmapk2/Δmapk2 clone were able to grow normally and exhibited no detectable phenotype. When these cells were triggered to differentiate in vitro, however, they developed to the procyclic (fly midgut) form with delayed kinetics and subsequently underwent cell cycle arrest. Introduction of an ectopic copy of theTbMAPK2 gene into the null mutant restored its ability to differentiate and to divide. In contrast, a TbMAPK2mutant, in which the T190 and Y192 residues of the activating phosphorylation site were replaced by A and F, was unable to restore the growth and differentiation phenotypes. Analysis of the DNA content and the nucleus/kinetoplast configuration of individual cells showed that the null mutant was arrested in all phases of the cell cycle and that 25–30% of the cells had failed to segregate their nucleus and kinetoplast correctly. This implies that cell cycle progression by the procyclic form depends on a constitutive stimulus exerted by the signaling cascade operating through TbMAPK2.
SUPERSYMMETRIC APPROACH TO EXACTLY SOLVABLE SYSTEMS WITH POSITION-DEPENDENT EFFECTIVE MASSES
Authors: GÖNÜL BEŞİ , GÖNÜL BÜLENT , TUTCU DİLEK , ÖZER OKAN
Published: November 2002

We discuss the relationship between exact solvability of the Schrödinger equation with a position-dependent mass and the ordering ambiguity in the Hamiltonian operator within the framework of supersymmetric quantum mechanics. The one-dimensional Schrödinger equation, derived from the general form of the effective mass Hamiltonian, is solved exactly for a system with exponentially changing mass in the presence of a potential with similar behaviour, and the corresponding supersymmetric partner Hamiltonians are related to the effective-mass Hamiltonians proposed in the literature.
THE SCALAR ETHER-THEORY OF GRAVITATION AND ITS FIRST TEST IN CELESTIAL MECHANICS
Authors: ARMINJON MAYEUL
Published: November 2002

The motivations for investigating a theory of gravitation based on a concept of "ether" are discussed — a crucial point is the existence of an alternative interpretation of special relativity, named the Lorentz-Poincaré ether theory. The basic equations of one such theory of gravity, based on just one scalar field, are presented. To check this theory in celestial mechanics, an "asymptotic" scheme of post-Newtonian (PN) approximation is summarized and its difference with the standard PN scheme is emphasized. The derivation of PN equations of motion for the mass centers, based on the asymptotic scheme, is outlined. They are implemented for the major bodies of the solar system and the prediction for Mercury is compared with an ephemeris based on general relativity.
QUINTESSENTIAL POTENTIAL, FERMION FAMILIES AND SPONTANEOUS BREAKING OF SCALE SYMMETRY
Authors: GUENDELMAN E. I. , KAGANOVICH A. B.
Published: November 2002

We study a generally covariant model with SSB of scale invariance where two measures of integration in the action enter: the standard [Formula: see text] and a new Φd4x, where Φ is a density built out of degrees of freedom independent of the metric. The theory demonstrates a new mechanism for generation of the exponential potential: in the conformal Einstein frame, after SSB of scale invariance, the theory develops the exponential potential and, in general, non-linear kinetic term is generated as well. The scale symmetry does not allow the appearance of terms breaking the exponential shape of the potential that solves the problem of the flatness of the scalar field potential in the context of quintessential scenarios. Under normal laboratory conditions where the fermionic matter dominates, it is found that starting from a single fermionic field we obtain exactly three different types of spin 1/2 particles which can be identified with known fermion families. It is automatically achieved that for two of them, fermion masses are constants, the energy-momentum tensor is canonical and the "fifth force" is absent. For the third family, a self-interaction appears as a result of SSB of scale invariance.
Ability of Recombinant Factor VIIa to Reverse the Anticoagulant Effect of the Pentasaccharide Fondaparinux in Healthy Volunteers
Authors: Bijsterveld Nick R. , Moons Arno H. , Boekholdt S. Matthijs , van Aken Benien E. , Fennema Hein , Peters Ron J.G. , Meijers Joost C.M. , Büller Harry R. , Levi Marcel
Published: November 2002

Background—

The novel anticoagulant fondaparinux proved to be effective and safe in the postoperative prevention of venous thrombosis. Current phase III trials with this synthetic selective factor Xa inhibitor focus on its use in the treatment of patients with venous and arterial thrombosis. As with any anticoagulant therapy, there is a risk of bleeding complications; hence, a strategy to reverse the effects of fondaparinux is desirable. The aim of this study was to investigate whether recombinant factor VIIa (rFVIIa) could neutralize the anticoagulant effects of subcutaneously administered fondaparinux.

Methods and Results—

In a randomized, placebo-controlled design, 16 healthy male subjects received either a single subcutaneous dose of fondaparinux (10 mg) and a single intravenous bolus of rFVIIa (90 μg/kg; n=8), fondaparinux and placebo (n=4), or placebo and rFVIIa (n=4). Fondaparinux (or placebo) was administered 2 hours before rFVIIa (or placebo). Injection of rFVIIa after fondaparinux normalized the prolonged activated partial thromboplastin and prothrombin times and reversed the decrease in prothrombin activation fragments 1+2 (F
1+2
), as observed with fondaparinux alone. Thrombin-generation time and endogenous thrombin potential, which were inhibited by fondaparinux, normalized up to 6 hours after rFVIIa injection.

Conclusions—

rFVIIa is capable of normalizing coagulation times and thrombin generation during fondaparinux treatment. The duration of this effect ranged from 2 to 6 hours after rFVIIa injection. These results suggest that rFVIIa may be useful to reverse the anticoagulant effect of fondaparinux in case of serious bleeding complications or need for acute surgery during treatment with fondaparinux.
Contribuciones de la Psicología Social al estudio de la satisfacción de los usuarios y consumidores
Authors: Martínez-Tur Vicente , Peiró José M. , Ramos José , Tordera Núria
Published: November 2002

En este trabajo se realiza una revisión de las contribuciones realizadas en el ámbito de la psicología social al estudio de la satisfacción de los usuarios y consumidores. En concreto, se constata que la investigación se ha realizado predominan temente des de acercamientos cognitivos (confirmación de expectativas, equidad, atribución causal) y, en menor medida, en afectivos. Se señalan, asimismo, las principales limitaciones relacionadas con el escaso valor diagnóstico de la información, la consideración los atributos inestables de rendimiento de los productos y/o servicios, el estudio de relaciones complejas entre constructos, la utilización de medidas agregadas de satisfacción y el estudio del trabajo emocional. También se ofrecen algunas consideraciones relevantes para investigaciones futuras.
Familia y psicología social: una relación sin formalizar
Authors: Gracia Enrique , Musitu Gonzalo
Published: November 2002

En este artículo se reflexiona sobre la escasa atención que la psicología social ha prestado tradicionalmente a la familia. En primer lugar, se analiza si la familia está presente en los terrenos que tradicionalmenteacota la psicología social. En segundo lugar se realiza un estudio cuantitativoy cualitativos de la categoría “familia” en el Psychological Abstracts. En tercer lugar se hace una revisión de la principales áreas de investigación que han configurado el estudio de la familia en las ciencias sociales. Se constata que aunque la relación de la familia y la psicología social no se ha formalizado o institucionalizado (en términos de su presencia en manuales o en su formato como disciplina), si que se puede decir que existe una larga relación de hecho por la abundante investigación científica. Se finaliza con algunas reflexiones sobre algunos de los objetivos y metas de la psicología social de la familia.