bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental regulation of active and passive membrane properties in rat vibrissa motoneurones
Authors: Nguyen Quoc‐Thang , Wessel Ralf , Kleinfeld David
Published: February 2004

We characterized the electrophysiological properties of vibrissa motoneurones (vMNs) in rat. Intracellular recordings of vMNs in brainstem slices from animals aged P4 to P5 and P9 to P11, i.e. newborn animals, showed that the subthreshold membrane impedance has the form of passive decay. In particular, the impedance follows the 1/√f signature for long dendrites beyond a cut‐off frequency of fc= 8 Hz. In contrast, the impedance has the form of a resonant filter in vMNs from slices prepared from animals aged P17 to P23, i.e. young animals. The resonance has a peak near 4 Hz and an amplitude of 1.2 times that at low frequencies (f∼ 0.1Hz). The low frequency onset of the resonance is shown to depend on a hyperpolarization‐activated depolarizing current, Ih. This current functions as a high‐pass filter. The high frequency cut‐off of the resonance results from passive decay in long dendrites, similar to the case with newborn animals but with fc= 20Hz. In addition to a resonance in subthreshold properties, an enhanced resonance in spiking is observed in young as opposed to newborn animals. The transition from solely passive decay in vMNs from newborn animals to resonance in young animals coincides with the onset of whisking. Further, the width of the resonance encompasses the 4–15Hz range of exploratory whisking. Nonetheless, it remains to be shown if there is a causal relation between the regulation of currents in vMNs and the onset of whisking. In particular, we further observed that the membrane impedance of hypoglossal motoneurones from both newborn and young animals exhibits a subthreshold resonance that also peaks near 4Hz. The amplitude of this resonance increases from 1.1 to 1.4 times that at low frequencies in newborn versus young animals. We conjecture that resonance properties in vibrissa, hypoglossal, and potentially other motoneurones, may serve to transiently and purposely synchronize different orofacial behaviours.
Computational modeling of cell sorting, tissue engulfment, and related phenomena: A review
Authors: Brodland G Wayne
Published: February 2004

Embryonic cells have the remarkable ability to spontaneously reposition themselves with respect to other cells in an aggregate, an ability that is central to embryo morphogenesis, many disease processes, wound healing, and tissue engineering. In these rearrangements, cells of two or more histological types in a heterotypic aggregate can sort, mix or form checkerboard patterns and contacting fragments of different homogeneous tissues can spread over or engulf one another. In this article, the experimental literature on cell and tissue reorganization is summarized, the main sub-cellular structural components are identified and hypotheses about how these components interact to drive specific patterns of rearrangement are outlined. Making extensive use of tables, the article then maps out the interplay between experiments, theories, ultrastructural discoveries and computer models in the advancement of the field. The article summarizes the main computational approaches, including cell and sub-cellular lattices, body centric, boundary vertex and finite element models. The principle of operation, advantages and disadvantages of each approach is discussed, and the contributions of representative papers noted. Strong commonalities are found in the physical basis of the models and in the predictions they make. Computational models provide an important ongoing complement to experimental and theoretical studies. This review article cites 154 references.
Bed forms in turbulent channel flow
Authors: Gyr and Albert , Kinzelbach Wolfgang
Published: February 2004

Bed forms in channels result from the interaction between sediment transport, turbulence and gravitational settling. They document mechanisms of self-organization between flow structures and the developing structure of the bed. It is shown that these mechanisms can be characterized by length scales of the sediment, the bed form and the flow structure. Three types of interaction can be distinguished: 1) The first type of mechanisms can be observed at beds of sediment with grain diameter smaller than the typical structural dimension of turbulence. It is shown how with increasing hydraulic loading of the bed a hydraulically smooth surface develops structures, which turn from “orange peel” to stripe and arrowhead patterns and finally into ripples. This group of bed forms is limited to a grain diameter of d+=12.5 in viscous units. In the regime of the stripe structures drag reduction occurs. 2) If grains or bed forms reach a height, which leads to separation, a completely different regime prevails, which is determined by the self-organization of separation zones. A prominent example for these bed forms are dunes. 3) Demixing processes, secondary flows and roughness contrasts finally lead to the development of longitudinal and transverse banks. All three mechanisms are explained on the basis of kinematic models and documented by experimental data. Emphasis is put on the two-dimensionalization of bed forms in a highly 3-dimensional (3D) turbulent flow, which is traced back to the self organization of vortex systems. This review article contains 55 references.
Architecture of the Photosynthetic Oxygen-Evolving Center
Authors: Ferreira Kristina N. , Iverson Tina M. , Maghlaoui Karim , Barber James , Iwata So
Published: February 2004

Photosynthesis uses light energy to drive the oxidation of water at an oxygen-evolving catalytic site within photosystem II (PSII). We report the structure of PSII of the cyanobacterium
Thermosynechococcus elongatus
at 3.5 angstrom resolution. We have assigned most of the amino acid residues of this 650-kilodalton dimeric multisubunit complex and refined the structure to reveal its molecular architecture. Consequently, we are able to describe details of the binding sites for cofactors and propose a structure of the oxygen-evolving center (OEC). The data strongly suggest that the OEC contains a cubane-like Mn
3
CaO
4
cluster linked to a fourth Mn by a mono-μ-oxo bridge. The details of the surrounding coordination sphere of the metal cluster and the implications for a possible oxygen-evolving mechanism are discussed.
The Structure and Receptor Binding Properties of the 1918 Influenza Hemagglutinin
Authors: Gamblin S. J. , Haire L. F. , Russell R. J. , Stevens D. J. , Xiao B. , Ha Y. , Vasisht N. , Steinhauer D. A. , Daniels R. S. , Elliot A. , Wiley D. C. , Skehel J. J.
Published: February 2004

The 1918 influenza pandemic resulted in about 20 million deaths. This enormous impact, coupled with renewed interest in emerging infections, makes characterization of the virus involved a priority. Receptor binding, the initial event in virus infection, is a major determinant of virus transmissibilitythat, for influenza viruses, is mediated by the hemagglutinin (HA) membrane glycoprotein. We have determined the crystal structures of the HA from the 1918 virus and two closelyrelated HAs in complex with receptor analogs. Theyexplain how the 1918 HA, while retaining receptor binding site amino acids characteristic of an avian precursor HA, is able to bind human receptors and how, as a consequence, the virus was able to spread in the human population.
Winged Helix Transcription Factor CPCR1 Is Involved in Regulation of β-Lactam Biosynthesis in the Fungus
Acremonium chrysogenum
Authors: Schmitt Esther K. , Bunse Astrid , Janus Danielle , Hoff Birgit , Friedlin Ernst , Kürnsteiner Hubert , Kück Ulrich
Published: February 2004

Winged helix transcription factors, including members of the forkhead and the RFX subclasses, are characteristic for the eukaryotic domains in animals and fungi but seem to be missing in plants. In this study, in vitro and in vivo approaches were used to determine the functional role of the RFX transcription factor CPCR1 from the filamentous fungus
Acremonium chrysogenum
in cephalosporin C biosynthesis. Gel retardation analyses were applied to identify new binding sites of the transcription factor in an intergenic promoter region of cephalosporin C biosynthesis genes. Here, we illustrate that CPCR1 recognizes and binds at least two sequences in the intergenic region between the
pcbAB
and
pcbC
genes. The in vivo relevance of the two sequences for gene activation was demonstrated by using
pcbC
promoter-
lacZ
fusions in
A. chrysogenum
. The deletion of both CPCR1 binding sites resulted in an extensive reduction of reporter gene activity in transgenic strains (to 12% of the activity level of the control). Furthermore,
Acremonium
transformants with multiple copies of the
cpcR1
gene and knockout strains support the idea of CPCR1 being a regulator of cephalosporin C biosynthesis gene expression. Significant differences in
pcbC
gene transcript levels were obtained with the knockout transformants. More-than-twofold increases in the
pcbC
transcript level at 24 and 36 h of cultivation were followed by a reduction to approximately 80% from 48 to 96 h in the knockout strain. The overall levels of the production of cephalosporin C were identical in transformed and nontransformed strains; however, the knockout strains showed a striking reduction in the level of the biosynthesis of intermediate penicillin N to less than 20% of that of the recipient strain. We were able to show that the complementation of the
cpcR1
gene in the knockout strains reverses
pcbC
transcript and penicillin N amounts to levels comparable to those in the control. These results clearly indicate the involvement of CPCR1 in the regulation of cephalosporin C biosynthesis. However, the complexity of the data points to a well-controlled or even functional redundant network of transcription factors, with CPCR1 being only one player within this process.
An
ste20
Homologue in
Ustilago maydis
Plays a Role in Mating and Pathogenicity
Authors: Smith David G. , Garcia-Pedrajas Maria D. , Hong Wei , Yu Zhanyang , Gold Scott E. , Perlin Michael H.
Published: February 2004

The mitogen-activated protein kinase (MAPK) pathways are conserved from fungi to humans and have been shown to play important roles in mating and filamentous growth for both
Saccharomyces cerevisiae
and dimorphic fungi and in infectivity for pathogenic fungi.
STE20
encodes a protein kinase of the p21-activated protein kinase family that regulates more than one of these cascades in yeasts. We hypothesized that an Ste20p homologue would play a similar role in the dimorphic plant pathogen
Ustilago maydis
. The full-length copy of the
U. maydis
gene was obtained from a genomic library; it lacked introns and was predicted to encode a protein of 826 amino acids, whose sequence confirmed its identity as the first Ste20p homologue to be isolated from a plant pathogen. The predicted protein contained both an N-terminal regulatory Cdc42-Rac interactive binding domain and a C-terminal catalytic kinase domain. Disruption of the gene
smu1
resulted in a delayed mating response in a mating-type-specific manner and also in a severe reduction in disease production on maize. Unlike the
Ustilago
bypass of cyclase (
ubc
) mutations previously identified in genes in the pheromone-responsive MAPK cascade, mutation of
smu1
does not by itself act as an extragenic suppressor of the filamentous phenotype of a
uac1
mutant. Thus, the direct connection of Smu1p to MAPK cascade function has yet to be established. Even so, Smu1, though not absolutely required for mating, is necessary for wild-type mating and pathogenicity.
Candida albicans
Lacking the Gene Encoding the Regulatory Subunit of Protein Kinase A Displays a Defect in Hyphal Formation and an Altered Localization of the Catalytic Subunit
Authors: Cassola Alejandro , Parrot Marc , Silberstein Susana , Magee Beatrice B. , Passeron Susana , Giasson Luc , Cantore María L.
Published: February 2004

The fungal pathogen
Candida albicans
switches from a yeast-like to a filamentous mode of growth in response to a variety of environmental conditions. We examined the morphogenetic behavior of
C. albicans
yeast cells lacking the
BCY1
gene, which encodes the regulatory subunit of protein kinase A. We cloned the
BCY1
gene and generated a
bcy1 tpk2
double mutant strain because a homozygous
bcy1
mutant in a wild-type genetic background could not be obtained. In the
bcy1 tpk2
mutant, protein kinase A activity (due to the presence of the
TPK1
gene) was cyclic AMP independent, indicating that the cells harbored an unregulated phosphotransferase activity. This mutant has constitutive protein kinase A activity and displayed a defective germinative phenotype in
N
-acetylglucosamine and in serum-containing medium. The subcellular localization of a Tpk1-green fluorescent protein (GFP) fusion protein was examined in wild-type,
tpk2
null, and
bcy1 tpk2
double mutant strains. The fusion protein was observed to be predominantly nuclear in wild-type and
tpk2
strains. This was not the case in the
bcy1 tpk2
double mutant, where it appeared dispersed throughout the cell. Coimmunoprecipitation of Bcy1p with the Tpk1-GFP fusion protein demonstrated the interaction of these proteins inside the cell. These results suggest that one of the roles of Bcy1p is to tether the protein kinase A catalytic subunit to the nucleus.
Regulatory Network Connecting Two Glucose Signal Transduction Pathways in
Saccharomyces cerevisiae
Authors: Kaniak Aneta , Xue Zhixiong , Macool Daniel , Kim Jeong-Ho , Johnston Mark
Published: February 2004

The yeast
Saccharomyces cerevisiae
senses glucose, its preferred carbon source, through multiple signal transduction pathways. In one pathway, glucose represses the expression of many genes through the Mig1 transcriptional repressor, which is regulated by the Snf1 protein kinase. In another pathway, glucose induces the expression of
HXT
genes encoding glucose transporters through two glucose sensors on the cell surface that generate an intracellular signal that affects function of the Rgt1 transcription factor. We profiled the yeast transcriptome to determine the range of genes targeted by this second pathway. Candidate target genes were verified by testing for Rgt1 binding to their promoters by chromatin immunoprecipitation and by measuring the regulation of the expression of promoter
lacZ
fusions. Relatively few genes could be validated as targets of this pathway, suggesting that this pathway is primarily dedicated to regulating the expression of
HXT
genes. Among the genes regulated by this glucose signaling pathway are several genes involved in the glucose induction and glucose repression pathways. The Snf3/Rgt2-Rgt1 glucose induction pathway contributes to glucose repression by inducing the transcription of
MIG2
, which encodes a repressor of glucose-repressed genes, and regulates itself by inducing the expression of
STD1
, which encodes a regulator of the Rgt1 transcription factor. The Snf1-Mig1 glucose repression pathway contributes to glucose induction by repressing the expression of
SNF3
and
MTH1
, which encodes another regulator of Rgt1, and also regulates itself by repressing the transcription of
MIG1
. Thus, these two glucose signaling pathways are intertwined in a regulatory network that serves to integrate the different glucose signals operating in these two pathways.
Wangiella(Exophiala)dermatitidisWdChs5p, a Class V Chitin Synthase, Is Essential for Sustained Cell Growth at Temperature of Infection
Authors: Liu Hongbo , Kauffman Sarah , Becker Jeffrey M. , Szaniszlo Paul J.
Published: February 2004

The chitin synthase structural geneWdCHS5was isolated from the black fungal pathogen of humansWangielladermatitidis. Sequence analysis revealed that the gene has a myosin motor-like-encoding region at its 5′ end and a chitin synthase (class V)-encoding region at its 3′ end. Northern blotting showed thatWdCHS5is expressed at high levels under conditions of stress. Analysis of the 5′ upstream region ofWdCHS5fused to a reporter gene indicated that one or more of the potential regulatory elements present may have contributed to the high expression levels. Disruption ofWdCHS5produced mutants that grow normally at 25°C but have severe growth and cellular abnormalities at 37°C. Osmotic stabilizers, such as sorbitol and sucrose, rescued the wild-type phenotype, which indicated that the loss of WdChs5p causes cell wall integrity defects. Animal survival tests with a mouse model of acute infection showed that allwdchs5Δ mutants are less virulent than the parental strain. Reintroduction of theWdCHS5gene into thewdchs5Δ mutants abolished the temperature-sensitive phenotype and reestablished their virulence. We conclude that the product ofWdCHS5is required for the sustained growth ofW. dermatitidisat 37°C and is of critical importance to its virulence.
C-Terminal Truncation of α-COP Affects Functioning of Secretory Organelles and Calcium Homeostasis in
Hansenula polymorpha
Authors: Chechenova Maria B. , Romanova Nina V. , Deev Alexander V. , Packeiser Anna N. , Smirnov Vladimir N. , Agaphonov Michael O. , Ter-Avanesyan Michael D.
Published: February 2004

In eukaryotic cells, COPI vesicles retrieve resident proteins to the endoplasmic reticulum and mediate intra-Golgi transport. Here, we studied the
Hansenula polymorpha
homologue of the
Saccharomyces cerevisiae RET1
gene, encoding α-COP, a subunit of the COPI protein complex.
H. polymorpha ret1
mutants, which expressed truncated α-COP lacking more than 300 C-terminal amino acids, manifested an enhanced ability to secrete human urokinase-type plasminogen activator (uPA) and an inability to grow with a shortage of Ca
2+
ions, whereas a lack of α-COP expression was lethal. The α-COP defect also caused alteration of intracellular transport of the glycosylphosphatidylinositol-anchored protein Gas1p, secretion of abnormal uPA forms, and reductions in the levels of Pmr1p, a Golgi Ca
2+
-ATPase. Overexpression of Pmr1p suppressed some
ret1
mutant phenotypes, namely, Ca
2+
dependence and enhanced uPA secretion. The role of COPI-dependent vesicular transport in cellular Ca
2+
homeostasis is discussed.
DNA Repair Functions That Control Sensitivity to Topoisomerase-Targeting Drugs
Authors: Malik Mobeen , Nitiss John L.
Published: February 2004

DNA topoisomerases play critical roles in a wide range of cellular processes by altering DNA topology to facilitate replication, transcription, and chromosome segregation. Topoisomerases alter DNA topology by introducing transient DNA strand breaks that involve a covalent protein DNA intermediate. Many agents have been found to prevent the religation of DNA strand breaks induced by the enzymes, thereby converting the enzymes into DNA-damaging agents. Repair of the DNA damage induced by topoisomerases is significant in understanding drug resistance arising following treatment with topoisomerase-targeting drugs. We have used the fission yeast
Schizosaccharomyces pombe
to identify DNA repair pathways that are important for cell survival following drug treatment.
S. pombe
strains carrying mutations in genes required for homologous recombination such as
rad22A
or
rad32
(homologues of
RAD52
and
MRE11
) are hypersensitive to drugs targeting either topoisomerase I or topoisomerase II. In contrast to results observed with
Saccharomyces cerevisiae
,
S. pombe
strains defective in nucleotide excision repair are also hypersensitive to topoisomerase-targeting agents. The loss of DNA replication or DNA damage checkpoints also sensitizes cells to both topoisomerase I and topoisomerase II inhibitors. Finally, repair genes (such as the

S. pombe rad8
+

gene) with no obvious homologs in other systems also play important roles in causing sensitivity to topoisomerase drugs. Since the pattern of sensitivity is distinct from that seen with other systems (such as the
S. cerevisiae
system), our results highlight the usefulness of
S. pombe
in understanding how cells deal with the unique DNA damage induced by topoisomerases.
Research ethics committees and paternalism
Authors: Edwards S J L , Kirchin S , Huxtable R
Published: February 2004

In this paper the authors argue that research ethics committees (RECs) should not be paternalistic by rejecting research that poses risk to people competent to decide for themselves. However it is important they help to ensure valid consent is sought from potential recruits and protect vulnerable people who cannot look after their own best interests. The authors first describe the tragic deaths of Jesse Gelsinger and Ellen Roche. They then discuss the following claims to support their case: (1) competent individuals are epistemologically and ethically in the best position to say which risks are reasonable for them, so RECs should be no more restrictive than the “normal” constraints on people taking risks with themselves; (2) RECs do not judge individual competence (that is for researchers and psychiatrists); (3) individual liberty is mostly limited by what serves the public interest, and RECs do not determine public interest; (4) RECs may have a paternalistic role in preventing exploitation of competent people vulnerable to the use of incentives, and in protecting the interests of incompetent people; however, (5) the moral and political authority of RECs has not been established in this respect.
Randomisation in trials: do potential trial participants understand it and find it acceptable?
Authors: Kerr C , Robinson E , Stevens A , Braunholtz D , Edwards S , Lilford R
Published: February 2004

Objective:To examine lay persons’ ability to identify methods of random allocation and their acceptability of using methods of random allocation in a clinical trial context.

Design:Leaflets containing hypothetical medical, non-medical, and clinical trial scenarios involving random allocation, using material from guidelines for trial information leaflets.

Setting and participants:Adults attending further education colleges (n = 130), covering a wide range of ages, occupations, and levels of education.

Main measures:Judgements of whether each of five methods of allocation to two groups was random in a medical or non-medical scenario. Judgements of whether these allocation methods were acceptable in a randomised clinical trial scenario, with or without a scientific justification for randomisation.

Results:The majority of our group of participants judged correctly that allowing people their preference was not random, and that the following were random: using a computer with no information about the individual (recommended wording for MREC trial leaflets), tossing a coin, drawing a name out of a hat. Judgements were split over allocating people in turn (not a random allocation method but shares features with randomisation). Judgements were no different in medical and non-medical scenarios. Few of the correctly identified random methods were judged to be acceptable in a clinical trial scenario. Inclusion of a scientific justification for randomising significantly increased the acceptability of only one random method: allocation by computer.

Conclusions:Current UK guidelines’ recommended description of random allocation by computer seems warranted. However, while potential trial participants may understand what random allocation means, they may find it unacceptable unless offered an acceptable justification for its use.
Professional responsibilities of biomedical scientists in public discourse
Authors: Schüklenk U
Published: February 2004

This article describes how a small but vocal group of biomedical scientists propagates the views that either HIV is not the cause of AIDS, or that it does not exist at all. When these views were rejected by mainstream science, this group took its views and arguments into the public domain, actively campaigning via newspapers, radio, and television to make its views known to the lay public. I describe some of the harmful consequences of the group’s activities, and ask two distinct ethical questions: what moral obligations do scientists who hold such minority views have with regard to a scientifically untrained lay audience, and what moral obligations do mainstream newspapers and government politicians have when it comes to such views. The latter question will be asked because the “dissidents” succeeded for a number of years in convincing the South African government of the soundness of their views. The consequences of their stance affected millions of HIV infected South Africans severely.
Between universalism and relativism: a conceptual exploration of problems in formulating and applying international biomedical ethical guidelines
Authors: Tangwa G B
Published: February 2004

In this paper, the author attempts to explore some of the problems connected with the formulation and application of international biomedical ethical guidelines, with particular reference to Africa. Recent attempts at revising and updating some international medical ethical guidelines have been bedevilled by intractable controversies and wrangling regarding both the content and formulation. From the vantage position of relative familiarity with both African and Western contexts, and the privilege of having been involved in the revision and updating of one of the international ethical guidelines, the author reflects broadly on these issues and attempts prescribing an approach from both the theoretical and practical angles liable to mitigate, if not completely eliminate, some of the problems and difficulties.
Better governance in academic health sciences centres: moving beyond the Olivieri/Apotex Affair in Toronto
Authors: Ferris L E , Singer P A , Naylor C D
Published: February 2004

The Toronto experience suggests that there may be several general lessons for academic health sciences complexes to learn from the Olivieri/Apotex affair (OAA) regarding the ethics, independence, and integrity of clinical research sponsored by for profit enterprises. From a local perspective, the OAA occurred when there already was a focus on the complex and changing relationships among the University of Toronto, its medical school, the fully affiliated teaching hospitals, and off campus faculty because of intertwined interests and responsibilities. The OAA became a catalyst that accelerated various systemic reforms, particularly concerning academic/industry relations. In this article, the evolving governance framework for the Toronto academic health sciences complex is reviewed and these policy and process reforms discussed. These reforms have created collaborative activity among research ethics boards and contract research offices of the partner institutions, and allowed the joint university/hospital ethics centre to play a role in governance and policy, while respecting the missions and mandates of the involved institutions. Although few of the policies are dramatically innovative, what is arguably novel is the elaboration of an overarching governance framework that aims to move ethics to a central focus in the academic complex. Time alone will tell how sustainable and effective these changes are.
The Olivieri debacle: where were the heroes of bioethics?
Authors: Baylis F
Published: February 2004

All Canadian bioethicists need to reflect on the meaning and value of their work, to see more clearly how the ethics of bioethics is being undermined from within. In the case involving Dr Olivieri, the Hospital for Sick Children, the University of Toronto, and Apotex Inc, there were countless opportunities for bioethical heroism. And yet, no bioethics heroes emerged from this case. Much has been written about the hospital’s and the university’s failures in this case. But what about the deafening silence from the Canadian bioethics community? Given the duty of bioethicists to “speak truth to power”, this silence is troubling. To date, nothing has been written about the silence. This article is intended as a partial remedy. As well, the article pays tribute to heretofore unsung heroes among Dr Olivieri’s research colleagues.
Whistleblowing in academic medicine
Authors: Rhodes R , Strain J J
Published: February 2004

Although medical centres have established boards, special committees, and offices for the review and redress of breaches in ethical behaviour, these mechanisms repeatedly prove themselves ineffective in addressing research misconduct within the institutions of academic medicine. As the authors see it, institutional design: (1) systematically ignores serious ethical problems, (2) makes whistleblowers into institutional enemies and punishes them, and (3) thereby fails to provide an ethical environment.

The authors present and discuss cases of academic medicine failing to address unethical behaviour in academic science and, thereby, illustrate the scope and seriousness of the problem. The Olivieri/Apotex affair is just another instance of academic medicine’s dereliction in a case of scientific fraud and misconduct. Instead of vigorously supporting their faculty member in her efforts to honestly communicate her findings and to protect patients from the risks associated with the use of the study drug, the University of Toronto collaborated with the Apotex company’s “stalling tactics,” closed down Dr Olivieri’s laboratory, harassed her, and ultimately dismissed her.

The authors argue that the incentives for addressing problematic behaviour have to be revised in order to effect a change in the current pattern of response that occurs in academic medicine. An externally imposed realignment of incentives could convert the perception of the whistleblower, from their present caste as the enemy within, into a new position, as valued friend of the institution. The authors explain how such a correction could encourage appropriate reactions to scientific misconduct from academic medicine.
ELECTRONIC STRUCTURE CALCULATIONS FORMoSe2USING EXTENDED HUCKEL TIGHT-BINDING METHOD
Authors: GALVAN DONALD H.
Published: February 2004

To gain insight into the electronic properties of MoSe2(molybdenum selenide, also known as drysdallite), electronic structure calculations, total and projected density of states, crystal orbital overlap population and Mulliken population analysis were performed. The calculated energy bands depict a semiconductor behavior with a direct gap (at K) of 0.91 eV and an indirect gap (from Γ to K) of 3.6 eV, respectively. Total and projected density of states provided information about the contribution from each orbital of each atom to the total density of states. Moreover, the bonding strength between some atoms within the unit cell was obtained. Mulliken population analysis corroborates the electron filling of the Mo dz2orbitals in agreement with another experimental and theoretical results.
THE RELATION BETWEEN CONSERVED NOISE RESTRICTED SOLID-ON-SOLID MODEL AND RESTRICTED CURVATURE MODEL
Authors: KIM JIN MIN
Published: February 2004

We introduce a Conserved Noise Restricted Solid-On-Solid (CNRSOS) model. The surface width W of the model grows as tβcn at the beginning with βcn≈0.12 and becomes saturated at Lαcn for t≫Lz with αcn≈0.49, where L is the system size. We find a one-to-one mapping between the CNRSOS model and the Restricted Curvature (RC) model by interpreting the height difference of the RC model as the height of the CNRSOS model. Therefore, there exist some relations, αrc-1=αcn and [Formula: see text], where the subscripts rc and cn are for the RC model and the CNRSOS model respectively.
Electron microprobe analysis of ouabain-exposed ciliary epithelium: PE-NPE cell couplets form the functional units
Authors: McLaughlin Charles W. , Zellhuber-McMillan Sylvia , Macknight Anthony D. C. , Civan Mortimer M.
Published: February 2004

Aqueous humor is secreted by the bilayered ciliary epithelium. Solutes and water enter the pigmented ciliary epithelial (PE) cell layer, cross gap junctions into the nonpigmented ciliary epithelial (NPE) cell layer, and are released into the aqueous humor. Electrical measurements suggest that heptanol reduces transepithelial ion movement by interrupting PE-NPE communication and that gap junctions may be a regulatory site of aqueous humor formation. Several lines of evidence also suggest that net ciliary epithelial transport is strongly region dependent. Divided rabbit iris-ciliary bodies were incubated in chambers under control and experimental conditions, quick-frozen, cryosectioned, and freeze-dried. Elemental intracellular contents of NPE and PE cells were determined by electron probe X-ray microanalysis. With or without heptanol, ouabain produced concentration- and time-dependent changes more markedly in anterior than in posterior epithelium. Without heptanol, there were considerable cell-to-cell variations in Na gain and K loss. However, contiguous NPE and PE cells displayed similar changes, even when nearby cell pairs were little changed by ouabain in aqueous, stromal, or both reservoirs. In contrast, with heptanol present, ouabain added to aqueous or both reservoirs produced much larger changes in NPE than in PE cells. The results indicate that 1) heptanol indeed interrupts PE-NPE junctions, providing an opportunity for electron microprobe analysis of the sidedness of modification of ciliary epithelial secretion; 2) Na and K undergo faster turnover in anterior than in posterior epithelium; and 3) PE-NPE gap junctions differ from PE-PE and NPE-NPE junctions in permitting ionic equilibration between adjoining ouabain-stressed cells.
Collagen I upregulates extracellular matrix gene expression and secretion of TGF-β1 by cultured human mesangial cells
Authors: Ortega-Velazquez R. , Gonzalez-Rubio M. , Ruiz-Torres M. P. , Diez-Marques M. L. , Iglesias M. C. , Rodríguez-Puyol M. , Rodríguez-Puyol D.
Published: February 2004

Progressive renal diseases are characterized by an increased synthesis of extracellular matrix (ECM) components. The mechanisms involved in the development of these alterations are not completely known, but a crucial role for TGF-β1 has been suggested. Moreover, the ability of the ECM to modulate the phenotypic expression of different cell types has been widely described. In experiments presented here, human mesangial cells (HMC) were grown on collagen type I (COL I) or IV (COL IV). ECM protein and TGF-β1 mRNA expression were evaluated by Northern blot analysis, and TGF-β1 secretion was evaluated by ELISA. The involvement of tyrosine kinase and serine-threonine kinase pathways was studied by Western blot analysis, immunofluorescence, and in vitro kinase assays. HMC cultured on COL I showed an increased mRNA expression of COL I and COL IV, fibronectin, and TGF-β1. Both tyrosine phosphorylation and integrin-linked kinase (ILK) activity increased when HMC were cultured on COL I, and blockade of these pathways inhibited the increased secretion of TGF-β1. In conclusion, the present results support a role for extracellular COL I in the regulation of TGF-β1 synthesis during progressive renal sclerosis and fibrosis and the subsequent increase in newly synthesized ECM proteins. In addition, ILK, along with the tyrosine kinases, participates in the genesis of this effect.
Regulation of neonatal liver protein synthesis by insulin and amino acids in pigs
Authors: O'Connor Pamela M. J. , Kimball Scot R. , Suryawan Agus , Bush Jill A. , Nguyen Hanh V. , Jefferson Leonard S. , Davis Teresa A.
Published: February 2004

The high efficiency of protein deposition during the neonatal period is driven by high rates of protein synthesis, which are maximally stimulated after feeding. Infusion of amino acids, but not insulin, reproduces the feeding-induced stimulation of liver protein synthesis. To determine whether amino acid-stimulated liver protein synthesis is independent of insulin in neonates, and to examine the role of amino acids and insulin in the regulation of translation initiation in neonatal liver, we performed pancreatic glucose-amino acid clamps in overnight-fasted 7-day-old pigs. Pigs ( n = 9–12/group) were infused with insulin at 0, 10, 22, and 110 ng·kg−0.66·min−1to achieve 0, 2, 6, and 30 μU/ml insulin, respectively. At each insulin dose, amino acids were maintained at fasting or fed levels or, in conjunction with the highest insulin dose, allowed to fall to below fasting levels. Insulin had no effect on the fractional rate of protein synthesis in liver. Amino acids increased fractional protein synthesis rates in liver at each dose of insulin, including the 0 μU/ml dose. There was a dose-response effect of amino acids on liver protein synthesis. Amino acids and insulin increased protein S6 kinase and 4E-binding protein 1 (4E-BP1) phosphorylation; however, only amino acids decreased formation of the inactive 4E-BPI·eukaryotic initiation factor-4E (eIF4E) complex. The results suggest that amino acids regulate liver protein synthesis in the neonate by modulating the availability of eIF4E for 48S ribosomal complex formation and that this response does not require insulin.
Regulation of metabolic genes in human skeletal muscle by short-term exercise and diet manipulation
Authors: Arkinstall Melissa J. , Tunstall Rebecca J. , Cameron-Smith David , Hawley John A.
Published: February 2004

Changes in dietary macronutrient intake alter muscle and blood substrate availability and are important for regulating gene expression. However, few studies have examined the effects of diet manipulation on gene expression in human skeletal muscle. The aim of this study was to quantify the extent to which altering substrate availability impacts on subsequent mRNA abundance of a subset of carbohydrate (CHO)- and fat-related genes. Seven subjects consumed either a low- (LOW; 0.7 g/kg body mass CHO) or high- (HIGH; 10 g/kg body mass CHO) CHO diet for 48 h after performing an exhaustive exercise bout to deplete muscle glycogen stores. After intervention, resting muscle and blood samples were taken. Muscle was analyzed for the gene abundances of GLUT4, glycogenin, pyruvate dehydrogenase kinase-4 (PDK-4), fatty acid translocase (FAT/CD36), carnitine palmitoyltransferase I (CPT I), hormone-sensitive lipase (HSL), β-hydroxyacyl-CoA dehydrogenase (β-HAD), and uncoupling binding protein-3 (UCP3), and blood samples for glucose, insulin, and free fatty acid (FFA) concentrations. Glycogen-depleting exercise and HIGH-CHO resulted in a 300% increase in muscle glycogen content ( P < 0.001) relative to the LOW-CHO condition. FFA concentrations were twofold higher after LOW- vs. HIGH-CHO ( P < 0.05). The exercise-diet manipulation exerted a significant effect on transcription of all carbohydrate-related genes, with an increase in GLUT4 and glycogenin mRNA abundance and a reduction in PDK-4 transcription after HIGH-CHO (all P < 0.05). FAT/CD36 ( P < 0.05) and UCP3 ( P < 0.01) gene transcriptions were increased following LOW-CHO. We conclude that 1) there was a rapid capacity for a short-term exercise and diet intervention to exert coordinated changes in the mRNA transcription of metabolic related genes, and 2) genes involved in glucose regulation are increased following a high-carbohydrate diet.
Gastrin regulates the heparin-binding epidermal-like growth factor promoter via a PKC/EGFR-dependent mechanism
Authors: Sinclair Natalie F. , Ai Wandong , Raychowdhury Raktima , Bi Meixia , Wang Timothy C. , Koh Theodore J. , McLaughlin John T.
Published: February 2004

Gastrin is a known growth/differentiation factor for the gastric mucosa. Its effects are likely mediated by the induction of heparin-binding epidermal-like growth factor (HB-EGF), a member of the EGF family of growth factors that is expressed by gastric parietal cells. In this study, we investigated the regulation of the HB-EGF promoter by gastrin in a human gastric cancer cell line. Serial human HB-EGF promoter-luciferase reporter deletion constructs and heterologous promoter constructs were transfected into AGS-E cells and stimulated with gastrin (10−7M) with or without various signal transduction inhibitors. EMSA were also performed. Gastrin stimulation resulted in a fivefold increase in HB-EGF-luciferase activity. The cis-acting element mediating gastrin responsiveness was mapped to the −69 to −58 region of the HB-EGF promoter. Gastrin stimulation was PKC dependent and at least partially mediated by activation of the EGF receptor.
Quantitative hepatic phosphorus-31 magnetic resonance spectroscopy in compensated and decompensated cirrhosis
Authors: Corbin I. R. , Ryner L. N. , Singh H. , Minuk G. Y.
Published: February 2004

Few studies have examined the physiological/biochemical status of hepatocytes in patients with compensated and decompensated cirrhosis in situ. Phosphorus-31 magnetic resonance spectroscopy (31P MRS) is a noninvasive technique that permits direct assessments of tissue bioenergetics and phospholipid metabolism. Quantitative31P MRS was employed to document differences in the hepatic metabolite concentrations among patients with compensated and decompensated cirrhosis as well as healthy controls. All MRS examinations were performed on a 1.5-T General Electric Signa whole body scanner. The concentration of hepatic phosphorylated metabolites among patients with compensated cirrhosis ( n = 7) was similar to that among healthy controls ( n = 8). However, patients with decompensated cirrhosis ( n = 6) had significantly lower levels of hepatic ATP compared with patients with compensated cirrhosis and healthy controls ( P < 0.02 and P < 0.009, respectively) and a higher phosphomonoester/phosphodiester ratio than controls ( P < 0.003). The results of this study indicate that metabolic disturbances in hepatic energy and phospholipid metabolism exist in patients with decompensated cirrhosis that are not present in patients with compensated cirrhosis or healthy controls. These findings provide new insights into the pathophysiology of hepatic decompensation.
Lateral intercellular space volume as a determinant of CFTR-mediated anion secretion across small intestinal mucosa
Authors: Gawenis Lara R. , Boyle Kathryn T. , Palmer Bradley A. , Walker Nancy M. , Clarke Lane L.
Published: February 2004

Studies of full-thickness, small intestinal preparations have shown that maximal anion secretion [indexed by short-circuit current ( Isc)] during intracellular cAMP (cAMPi) stimulation is transient and followed by a decline toward baseline. Declining Isc is preceded by decreases in transepithelial conductance (Gt), which in the small intestine reflects the lateral intercellular space (LIS) volume of the paracellular pathway. We hypothesized that decreases in LIS volume limit the magnitude and duration of cAMPi-stimulated anion secretion. Experimental manipulations to increase the patency of the LIS (assessed by Gt and electron microscopy) were investigated for an effect on the magnitude of cAMPi-stimulated anion secretion (assessed by the Isc and isotopic fluxes) across murine small intestine. In control studies, changes of Gt after cAMPi stimulation were associated with a morphological “collapse” of the LIS, which did not occur in intestine of CFTR-null mice. Removal of the outer intestinal musculature, exposure to a serosal hypertonic solution, or increased serosal hydrostatic pressure minimized reductions in Gt and increased the cAMPi-stimulated Isc response. Increased Isc primarily resulted from increased Cl− secretion that was largely bumetanide sensitive. However, bumetanide-insensitive Isc was also increased, and similar increases occurred in the Na+-K+-2Cl− cotransporter (NKCC1)-null intestine, indicating that activities of non-NKCC1 anion uptake proteins are also affected by LIS volume. Thus LIS patency is an important determinant of the magnitude and duration of CFTR-mediated anion secretion in murine small intestine. Decreases in LIS volume may limit the pool of available anions to basolateral transporters involved in transepithelial secretion.
A novel framework of circulatory equilibrium
Authors: Uemura Kazunori , Sugimachi Masaru , Kawada Toru , Kamiya Atsunori , Jin Yintie , Kashihara Koji , Sunagawa Kenji
Published: February 2004

A novel framework of circulatory equilibrium was developed by extending Guyton's original concept. In this framework, venous return (COV) for a given stressed volume (V) was characterized by a flat surface as a function of right atrial pressure (PRA) and left atrial pressure (PLA) as follows: COV= V /W − GSPRA− GPPLA, where W, GS, and GPdenote linear parameters. In seven dogs under total heart bypass, COV, PRA, PLA, and V were varied to determine the three parameters in each animal with use of multivariate analysis. The coefficient of determination ( r2= 0.92–0.99) indicated the flatness of the venous return surface. The averaged surface was COV= V/0.129 − 19.61PRA− 3.49PLA. To examine the invariability of the surface parameters among animals, we predicted the circulatory equilibrium in response to changes in stressed volume in another 12 dogs under normal and heart failure conditions. This was achieved by equating the standard surface with the individually measured cardiac output (CO) curve. In this way, we could predict CO [ y = 0.90 x + 5.6, r2= 0.95, standard error of the estimate (SEE) = 8.7 ml·min−1·kg−1], PRA( y = 0.96 x, r2= 0.98, SEE = 0.2 mmHg), and PLA( y = 0.89 x + 0.5, r2= 0.98, SEE = 0.8 mmHg) reasonably well. We conclude that the venous return surface accurately represents the venous return properties of the systemic and pulmonary circulations. The characteristics of the venous return surface are invariable enough among animals, making it possible to predict circulatory equilibrium, even if those characteristics are unknown in individual animals.
Transcription activator protein 1 mediates α- but not β-adrenergic hypertrophic growth responses in adult cardiomyocytes
Authors: Taimor G. , Schlüter K.-D. , Best P. , Helmig S. , Piper H. M.
Published: February 2004

In some models of cardiac hypertrophy, activation of activator protein 1 (AP-1) correlates with growth. However, AP-1 is also activated by stimuli not involved in cardiac growth. This raises the following questions: does AP-1 plays a causal role for cardiomyocyte growth, and is this role model or stimulus dependent? We used a single model to address these questions, i.e., ventricular cardiomyocytes of adult rats, and two growth stimuli, i.e., α- and β-adrenoceptor agonists [10 μM phenylephrine (PE) and 1 μM isoprenaline (Iso), respectively]. After 1 h of stimulation with PE, mRNA expression of c-Fos and c-Jun was upregulated to 185 ± 32 and 132 ± 13% of control. Fos and Jun proteins formed the AP-1 complex. PE stimulated DNA binding activity of AP-1 to 165 ± 22% of control within 2 h and increased protein synthesis to 161 ± 27% of control and cross-sectional area to 126 ± 4% of control. Inhibition of AP-1 binding activity by cAMP response element (CRE) decoy oligonucleotides abolished both of these growth responses. Iso stimulated AP-1 binding activity to 203 ± 19% of control within 2 h and stimulated protein synthesis to 145 ± 17% of control. However, the growth effect of Iso was not abolished by CRE decoys: Iso increased protein synthesis to 158 ± 17% of control in the presence of CRE. In conclusion, AP-1 is a causal mediator of the α-adrenergic, but not the β-adrenergic, growth response of cardiomyocytes.