bluuebunny/crossref_metadata_2025 huggingface dataset:
Dihydropyridine Receptors as Voltage Sensors for a Depolarization-evoked, IP3R-mediated, Slow Calcium Signal in Skeletal Muscle Cells
Authors: Araya Roberto , Liberona José L. , Cárdenas J. César , Riveros Nora , Estrada Manuel , Powell Jeanne A. , Carrasco M. Angélica , Jaimovich Enrique
Published: December 2002

The dihydropyridine receptor (DHPR), normally a voltage-dependent calcium channel, functions in skeletal muscle essentially as a voltage sensor, triggering intracellular calcium release for excitation-contraction coupling. In addition to this fast calcium release, via ryanodine receptor (RYR) channels, depolarization of skeletal myotubes evokes slow calcium waves, unrelated to contraction, that involve the cell nucleus (Jaimovich, E., R. Reyes, J.L. Liberona, and J.A. Powell. 2000. Am. J. Physiol. Cell Physiol. 278:C998–C1010). We tested the hypothesis that DHPR may also be the voltage sensor for these slow calcium signals. In cultures of primary rat myotubes, 10 μM nifedipine (a DHPR inhibitor) completely blocked the slow calcium (fluo-3-fluorescence) transient after 47 mM K+ depolarization and only partially reduced the fast Ca2+ signal. Dysgenic myotubes from the GLT cell line, which do not express the α1 subunit of the DHPR, did not show either type of calcium transient following depolarization. After transfection of the α1 DNA into the GLT cells, K+ depolarization induced slow calcium transients that were similar to those present in normal C2C12 and normal NLT cell lines. Slow calcium transients in transfected cells were blocked by nifedipine as well as by the G protein inhibitor, pertussis toxin, but not by ryanodine, the RYR inhibitor. Since slow Ca2+ transients appear to be mediated by IP3, we measured the increase of IP3 mass after K+ depolarization. The IP3 transient seen in control cells was inhibited by nifedipine and was absent in nontransfected dysgenic cells, but α1-transfected cells recovered the depolarization-induced IP3 transient. In normal myotubes, 10 μM nifedipine, but not ryanodine, inhibited c-jun and c-fos mRNA increase after K+ depolarization. These results suggest a role for DHPR-mediated calcium signals in regulation of early gene expression. A model of excitation-transcription coupling is presented in which both G proteins and IP3 appear as important downstream mediators after sensing of depolarization by DHPR.
Influence of Permeant Ions on Gating in Cyclic Nucleotide–gated Channels
Authors: Holmgren Miguel
Published: December 2002

Cyclic nucleotide–gated channels are key components in the transduction of visual and olfactory signals where their role is to respond to changes in the intracellular concentration of cyclic nucleotides. Although these channels poorly select between physiologically relevant monovalent cations, the gating by cyclic nucleotide is different in the presence of Na+ or K+ ions. This property was investigated using rod cyclic nucleotide–gated channels formed by expressing the subunit 1 (or α) in HEK293 cells. In the presence of K+ as the permeant ion, the affinity for cGMP is higher than the affinity measured in the presence of Na+. At the single channel level, subsaturating concentrations of cGMP show that the main effect of the permeant K+ ions is to prolong the time channels remain open without major changes in the shut time distribution. In addition, the maximal open probability was higher when K+ was the permeant ion (0.99 for K+ vs. 0.95 for Na+) due to an increase in the apparent mean open time. Similarly, in the presence of saturating concentrations of cAMP, known to bind but unable to efficiently open the channel, permeant K+ ions also prolong the time channels visit the open state. Together, these results suggest that permeant ions alter the stability of the open conformation by influencing of the O→C transition.
TRPM7 Provides an Ion Channel Mechanism for Cellular Entry of Trace Metal Ions
Authors: Monteilh-Zoller Mahealani K. , Hermosura Meredith C. , Nadler Monica J.S. , Scharenberg Andrew M. , Penner Reinhold , Fleig Andrea
Published: December 2002

Trace metal ions such as Zn2+, Fe2+, Cu2+, Mn2+, and Co2+ are required cofactors for many essential cellular enzymes, yet little is known about the mechanisms through which they enter into cells. We have shown previously that the widely expressed ion channel TRPM7 (LTRPC7, ChaK1, TRP-PLIK) functions as a Ca2+- and Mg2+-permeable cation channel, whose activity is regulated by intracellular Mg2+ and Mg2+·ATP and have designated native TRPM7-mediated currents as magnesium-nucleotide–regulated metal ion currents (MagNuM). Here we report that heterologously overexpressed TRPM7 in HEK-293 cells conducts a range of essential and toxic divalent metal ions with strong preference for Zn2+ and Ni2+, which both permeate TRPM7 up to four times better than Ca2+. Similarly, native MagNuM currents are also able to support Zn2+ entry. Furthermore, TRPM7 allows other essential metals such as Mn2+ and Co2+ to permeate, and permits significant entry of nonphysiologic or toxic metals such as Cd2+, Ba2+, and Sr2+. Equimolar replacement studies substituting 10 mM Ca2+ with the respective divalent ions reveal a unique permeation profile for TRPM7 with a permeability sequence of Zn2+ ≈ Ni2+ >> Ba2+ > Co2+ > Mg2+ ≥ Mn2+ ≥ Sr2+ ≥ Cd2+ ≥ Ca2+, while trivalent ions such as La3+ and Gd3+ are not measurably permeable. With the exception of Mg2+, which exerts strong negative feedback from the intracellular side of the pore, this sequence is faithfully maintained when isotonic solutions of these divalent cations are used. Fura-2 quenching experiments with Mn2+, Co2+, or Ni2+ suggest that these can be transported by TRPM7 in the presence of physiological levels of Ca2+ and Mg2+, suggesting that TRPM7 represents a novel ion-channel mechanism for cellular metal ion entry into vertebrate cells.
Implications of somatic mutations in the AML1 gene in radiation-associated and therapy-related myelodysplastic syndrome/acute myeloid leukemia
Authors: Harada Hironori , Harada Yuka , Tanaka Hideo , Kimura Akiro , Inaba Toshiya
Published: December 2002

Somatically acquired point mutations of AML1/RUNX1 gene have been recently identified in rare cases of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). Moreover, germ line mutations of AML1 were found in an autosomal dominant disease, familial platelet disorder with predisposition to AML (FPD/AML), suggesting that AML1 mutants, as well as AML1 chimeras, contribute to the transformation of hematopoietic progenitors. In this report, we showed that AML1 point mutations were found in 6 (46%) of 13 MDS patients among atomic bomb (A-bomb) survivors in Hiroshima. Unlike acute or chronic leukemia patients among A-bomb survivors, MDS patients exposed relatively low-dose radiation and developed the disease after a long latency period. AML1 mutations also were found in 5 (38%) of 13 therapy-related AML/MDS patients who were treated with alkylating agents with or without local radiation therapy. In contrast, frequency of AML1 mutation in sporadic MDS patients was 2.7% (2 of 74). Among AML1 mutations identified in this study, truncated-type mutants lost DNA binding potential and trans-activation activity. All missense mutations with one exception (Gly42Arg) lacked DNA binding ability and down-regulated the trans-activation potential of wild-type AML1 in a dominant-negative fashion. The Gly42Arg mutation that was shared by 2 patients bound DNA even more avidly than wild-type AML1 and enhanced thetrans-activation potential of normal AML1. These results suggest that AML1 point mutations are related to low-dose radiation or alkylating agents and play a role distinct from that of leukemogenic chimeras as a result of chromosomal translocations caused by sublethal radiation or topoisomerase II inhibitors.
Outcome of transplantation of highly purified peripheral blood CD34+ cells with T-cell add-back compared with unmanipulated bone marrow or peripheral blood stem cells from HLA-identical sibling donors in patients with first chronic phase chronic myeloid leukemia
Authors: Elmaagacli Ahmet H. , Peceny Rudolf , Steckel Nina , Trenschel Rudolf , Ottinger Hellmut , Grosse-Wilde Hans , Schaefer Ulrich W. , Beelen Dietrich W.
Published: December 2002

Outcomes of highly purified CD34+ peripheral blood stem cell transplantation (PBSCT) for chronic phase chronic myeloid leukemia (CML) (n = 32) were compared with those of PBSCT (n = 19) and of bone marrow transplantation (BMT) (n = 22) in the HLA-compatible sibling donor setting. Median follow-up was 18 months after CD34+-PBSCT and unmanipulated PBSCT and 20 months after BMT. CD34+-PBSCT was associated with delayed T-cell immune reconstitution at 3 months and 12 months after transplantation compared with PBSCT (P < .001) or BMT (not significant [NS]). The estimated probability of grades II to IV acute graft-versus-host disease (GVHD) was 60% ± 13% for the PBSCT group, 37% ± 13% for the BMT group, and only 14% ± 8% for the CD34+-PBSCT group (CD34-PBSCT versus BMT,P < .01; and CD34-PBSCT versus PBSCT,P < .001). The probabilities for molecular relapse were 88% for CD34+-PBSCT, 55% after BMT, and 37% after PBSCT (CD34+-PBSCT versus PBSCT,P < .03). Cytogenetic relapse probability was 58% after CD34+-PBSCT, 42% after BMT, and 28% after PBSCT (NS). After CD34+-PBSCT, 26 of 32 patients received a T-cell add-back. Hematologic relapse occurred in 4 of 22 patients after BMT, in 3 of 19 patients after PBSCT, and in only 1 of 32 patients after CD34+-PBSCT. The occurrence of a hematologic relapse in patients receiving CD34+-PBSC transplants was prevented by donor leukocyte infusions, which were applied at a median of 4 times (range, 1-7 times) with a median T-cell dose of 3.3 × 106 × kg/body weight [at a median] beginning at day 120 (range, 60-690 days). The estimated probability of 3-year survival after transplantation was 90% in the CD34+-PBSCT group, 68% in the PBSCT group, and 63% in the BMT group (CD34-PBSCT versus BMT, P < .01; and CD34-PBSCT versus PBSCT, P < .03). Transplantation of CD34+-PBSCs with T-cell add-back for patients with CML in first chronic phase seems to be safe and is an encouraging alternative transplant procedure to BMT or PBSCT.
The AML1-ETO fusion gene promotes extensive self-renewal of human primary erythroid cells
Authors: Tonks Alex , Pearn Lorna , Tonks Amanda J. , Pearce Laurence , Hoy Terry , Phillips Sarah , Fisher Janet , Downing James R. , Burnett Alan K. , Darley Richard L.
Published: December 2002

The t(8;21) translocation, which encodes the AML1-ETO fusion protein (now known as RUNX1-CBF2T1), is one of the most frequent translocations in acute myeloid leukemia, although its role in leukemogenesis is unclear. Here, we report that exogenous expression of AML1-ETO in human CD34+ cells severely disrupts normal erythropoiesis, resulting in virtual abrogation of erythroid colony formation. In contrast, in bulk liquid culture of purified erythroid cells, we found that while AML1-ETO initially inhibited proliferation during early (erythropoietin [EPO]–independent) erythropoiesis, growth inhibition gave way to a sustained EPO-independent expansion of early erythroid cells that continued for more than 60 days, whereas control cultures became growth arrested after 10 to 13 days (at the EPO-dependent stage of development). Phenotypic analysis showed that although these cells were CD13− and CD34−, unlike control cultures, these cells failed to up-regulate CD36 or to down-regulate CD33, suggesting that expression of AML1-ETO suppressed the differentiation of these cells and allowed extensive self-renewal to occur. In the early stages of this expansion, addition of EPO was able to promote both phenotypic (CD36+, CD33−, glycophorin A+) and morphologic differentiation of these cells, almost as effectively as in control cultures. However, with extended culture, cells expressing AML1-ETO became refractory to addition of this cytokine, suggesting that a block in differentiation had been established. These data demonstrate the capacity of AML1-ETO to promote the self-renewal of human hematopoietic cells and therefore support a causal role for t(8;21) translocations in leukemogenesis.
HGAL is a novel interleukin-4–inducible gene that strongly predicts survival in diffuse large B-cell lymphoma
Authors: Lossos Izidore S. , Alizadeh Ash A. , Rajapaksa Ranjani , Tibshirani Robert , Levy Ronald
Published: December 2002

We have cloned and characterized a novel human gene,HGAL (human germinal center–associated lymphoma), which predicts outcome in patients with diffuse large B-cell lymphoma (DLBCL). The HGAL gene comprises 6 exons and encodes a cytoplasmic protein of 178 amino acids that contains an immunoreceptor tyrosine-based activation motif (ITAM). It is highly expressed in germinal center (GC) lymphocytes and GC-derived lymphomas and is homologous to the mouse GC-specific gene M17. Expression of the HGAL gene is specifically induced in B cells by interleukin-4 (IL-4). Patients with DLBCL expressing high levels of HGAL mRNA demonstrate significantly longer overall survival than do patients with low HGAL expression. This association was independent of the clinical international prognostic index. High HGAL mRNA expression should be used as a prognostic factor in DLBCL.
Scianna antigens including Rd are expressed by ERMAP
Authors: Wagner Franz F. , Poole Joyce , Flegel Willy A.
Published: December 2002

The Scianna blood group encompasses the high-frequency antigens Sc1 and Sc3 and the low-frequency antigen Sc2. Another low-frequency antigen Rd (Radin) was suggested to belong to the Scianna blood group. The molecular basis of the Scianna blood group was unknown. The erythrocyte membrane-associated protein (ERMAP) shared the genomic location, protein product size, and localization to the red blood cell (RBC) membrane surface with Scianna. TheERMAP gene was sequenced in probands with known Scianna and Radin phenotypes. In a Sc:-1,-2 proband, only anERMAP allele with a 2-bp deletion in exon 3 causing a frameshift could be detected. A Sc:-1,2 proband was homozygous for theERMAP(Gly57Arg) allele. An Rd+proband was heterozygous for the ERMAP(Pro60Ala) allele. Polymerase chain reaction with sequence-specific priming (PCR-SSP) systems was developed to detect the Sc2 and Rd alleles of theERMAP gene. The 2 alleles occurred with about 1% and less than 1% frequency in the population, which was compatible with the frequency of the Sc2 and Rd antigens known in whites. Two Sc2+ and one Rd+ samples that were found by genotyping were confirmed by serology. The antigens of the Scianna blood group include Rd and are expressed by the human ERMAP protein. Sc2 is caused by an ERMAP(Gly57Arg) allele and Rd by an ERMAP(Pro60Ala) allele. Scianna is the last of the previously characterized protein-based blood group systems whose molecular basis was discerned. Hence, the phenotype prediction by genotyping became possible for all human blood group systems encoded by proteins.
Treatment of relapsed CD20+ Hodgkin lymphoma with the monoclonal antibody rituximab is effective and well tolerated: results of a phase 2 trial of the German Hodgkin Lymphoma Study Group
Authors: Rehwald Ute , Schulz Holger , Reiser Marcel , Sieber Markus , Staak Jan Oliver , Morschhauser Franck , Driessen Christoph , Rüdiger Thomas , Müller-Hermelink Konrad , Diehl Volker , Engert Andreas
Published: December 2002

This phase 2 trial was performed to evaluate the safety and efficacy of the chimeric monoclonal anti-CD20 antibody rituximab in patients with relapsed lymphocyte-predominant Hodgkin lymphoma or other CD20+ subtypes of Hodgkin disease (HD). Eligibility criteria required expression of the CD20 antigen on more than 30% of malignant cells. Fourteen patients were treated with 4 weekly intravenous infusions of rituximab (375 mg/m2). All patients had at least one prior chemotherapy (median, 2). The median time from first diagnosis was 9 years. Adverse events, such as rhinitis, fever, chills, and nausea, were usually transient and of mild to moderate grade, allowing outpatient treatment in most cases. All patients completed treatment and were eligible for a response. The overall response in 14 assessable patients was 86%, with 8 complete remissions and 4 partial remissions, and 2 patients with progressive disease. At a median follow-up of 12 months, 9 of 12 responders were in remission. The median duration of response has not been reached yet (20+ months). We conclude that rituximab is both safe and effective in a subgroup of CD20+ patients with HD.
Service innovations: second opinions in child and adolescent psychiatry
Authors: Richardson Greg , Cottrell David
Published: December 2002

AIMS AND METHODS

To devise a protocol, reflecting best practice, for obtaining second opinions in child and adolescent psychiatry through discussion with consultants in child and adolescent psychiatry within the Yorkshire region at their quarterly meetings.

Results

The major pressure for second opinions falls upon the Academic Unit of Child and Adolescent Mental Health and on the in-patient units. Other consultants who are considered to have specialist expertise in certain areas may also receive referrals for second opinions. Both consultants requesting and offering second opinions considered a protocol for obtaining them would be helpful to their practice.

Clinical Implications

An agreed protocol between consultants in child and adolescent psychiatry within a region ensures that young people with complex problems have access to second opinions on their diagnosis and management by consultants who can be recommended to referrers by other consultants. The network of consultants ensures such opinions are not requested excessively and that ‘rogue’ opinions without therapeutic follow-up are avoided.
NuMA and nuclear lamins behave differently in Fas-mediated apoptosis
Authors: Taimen Pekka , Kallajoki Markku
Published: December 2002

NuMA is a nuclear matrix protein that has an essential function in the organization of the mitotic spindle. Here we have studied the fate of NuMA in Fas-treated apoptotic Jurkat T and HeLa cells. We show that in both cell lines NuMA is an early target protein for caspases and that NuMA is cleaved coincidently with poly(ADP-ribose) polymerase-1 (PARP-1) and nuclear lamin B. NuMA is cleaved differently in Jurkat T and HeLa cells, suggesting that different sets of caspases are activated in these cell lines. The normal diffuse intranuclear distribution of NuMA changed during apoptosis: first NuMA condensed, then concentrated in the center of the nucleus and finally encircled the nuclear fragments within the apoptotic bodies. NuMA seems to be preferentially cleaved by caspase-3 in vivo since it was not cleaved in staurosporine-treated caspase-3-null MCF-7 breast cancer cells. The cleavage of NuMA, lamin B and PARP-1 was inhibited in the presence of three different caspase inhibitors: z-DEVD-FMK, z-VEID-FMK and z-IETD-FMK. Furthermore, in the presence of caspase inhibitors approximately 5-10% of the cells showed atypical apoptotic morphology. These cells had convoluted nuclei, altered chromatin structure and additionally, they were negative for NuMA and lamins. Since caspase-8, -3 and -7 were not activated and PARP was not cleaved in these cells as judged by western blotting and immunofluorescence studies, it is likely that this is an atypical form of programmed cell death owing to a proteinase(s) independent of caspases. These results characterize the role of NuMA in programmed cell death and suggest that cleavage of NuMA plays a role in apoptotic nuclear breakdown.
Sexy splicing: regulatory interplays governing sex determination fromDrosophilato mammals
Authors: Lalli Enzo , Ohe Kenji , Latorre Elisa , Bianchi Marco E. , Sassone-Corsi Paolo
Published: December 2002

A remarkable array of strategies is used to produce sexual differentiation in different species. Complex gene hierarchies govern sex determination pathways, as exemplified by the classic D. melanogaster paradigm,where an interplay of transcriptional, splicing and translational mechanisms operate. Molecular studies support the hypothesis that genetic sex determination pathways evolved in reverse order, from downstream to upstream genes, in the cascade. The recent identification of a role for the key regulatory factors SRY and WT1(+KTS) in pre-mRNA splicing indicates that important steps in the mammalian sex determination process are likely to operate at the post-transcriptional level.
A plant cyclin B2 is degraded early in mitosis and its ectopic expression shortens G2-phase and alleviates the DNA-damage checkpoint
Authors: Weingartner Magdalena , Pelayo Helvia R. , Binarova Pavla , Zwerger Karin , Melikant Balázs , de la Torre Consuelo , Heberle-Bors Erwin , Bögre László
Published: December 2002

Mitotic progression is timely regulated by the accumulation and degradation of A- and B-type cyclins. In plants, there are three classes of A-, and two classes of B-type cyclins, but their specific roles are not known. We have generated transgenic tobacco plants in which the ectopic expression of a plant cyclin B2 gene is under the control of a tetracycline-inducible promoter. We show that the induction of cyclin B2 expression in cultured cells during G2 phase accelerates the entry into mitosis and allows cells to override the replication checkpoint induced by hydroxyurea in the simultaneous presence of caffeine or okadaic acid, drugs that are known to alleviate checkpoint control. These results indicate that in plants, a B2-type cyclin is a rate-limiting regulator for the entry into mitosis and a cyclin B2-CDK complex might be a target for checkpoint control pathways. The cyclin B2 localization and the timing of its degradation during mitosis corroborate these conclusions: cyclin B2 protein is confined to the nucleus and during mitosis it is only present during a short time window until mid prophase, but it is effectively degraded from this timepoint onwards. Although cyclin B2 is not present in cells arrested by the spindle checkpoint in metaphase, cyclin B1 is accumulating in these cells. Ectopic expression of cyclin B2 in developing plants interferes with differentiation events and specifically blocks root regeneration, indicating the importance of control mechanisms at the G2- to M-phase transition during plant developmental processes.
The pairing of X and Y chromosomes during meiotic prophase in the marsupial species Thylamys elegans is maintained by a dense plate developed from their axial elements
Authors: Page Jesús , Berríos Soledad , Rufas Julio S. , Parra M. Teresa , Suja José Á. , Heyting Christa , Fernández-Donoso Raúl
Published: December 2002

Unlike eutherian males, pairing of the sex chromosomes in marsupial males during the first meiotic prophase is not mediated by a synaptonemal complex. Instead, a specific structure, the dense plate, develops during pachytene between the sex chromosomes. We have investigated the development and structural nature of this asynaptic association in males of the marsupial species Thylamys elegans by means of immunolabelling and electron microscopy techniques. Our results show that the behaviour of male marsupial sex chromosomes during first meiotic prophase is complex, involving modifications of their structure and/or composition. Pairing of the sex chromosomes and formation of the dense plate take place in mid pachytene,paralleling morphological changes in the sex chromosomal axial elements. Components of the central element of the synaptonemal complex were not found in the sex body, in agreement with ultrastructural studies that reported the absence of a canonical tripartite synaptonemal complex between male marsupial sex chromosomes. Interestingly, the dense plate is labelled with antibodies against the SCP3 protein of the lateral elements of the synaptonemal complex. Moreover, as sex chromosome axial elements decrease in mass throughout mid-late pachytene, the dense plate increases, suggesting that material moves from the axial elements to the dense plate. Additionally, both sex chromosome axial elements and the dense plate have proteins that are specifically phosphorylated, as revealed by their labelling with the MPM-2 antibody,indicating that they undergo a chromosome-specific regulation process throughout first meiotic prophase. We propose that the unique modifications of the composition and structure of the axial elements of the sex chromosomes in meiotic prophase may result in the proscription of synaptonemal complex formation between male marsupial sex chromosomes, where the dense plate is an extension of the axial elements of sex chromosomes. This replaces synapsis to maintain X and Y association during first meiotic prophase.
Heat shock and Cd2+ exposure regulate PML and Daxx release from ND10 by independent mechanisms that modify the induction of heat-shock proteins 70 and 25 differently
Authors: Nefkens Isabelle , Negorev Dmitri G. , Ishov Alexander M. , Michaelson Jennifer S. , Yeh Edward T. H. , Tanguay Robert M. , Müller Werner E. G. , Maul Gerd G.
Published: December 2002

Nuclear domains called ND10 or PML bodies might function as nuclear depots by recruiting or releasing certain proteins. Although recruitment of proteins through interferon-induced upregulation and SUMO-1 modification level of PML had been defined, it is not known whether release of proteins is regulated and has physiological consequences. Exposure to sublethal environmental stress revealed a sequential release of ND10-associated proteins. Upon heat shock Daxx and Sp100 were released but PML remained, whereas exposure to subtoxic concentrations of CdCl2 induced the release of ND10-associated proteins, including PML, with Sp100 remaining in a few sites. In both cases,recovery times were similar and were followed by a burst of mitotic activity. Cadmium-induced release of proteins from ND10 could be blocked by inhibiting activation of p38 MAPK or ERK1/2. By contrast, heat-shock-induced desumolation of PML and release of proteins from ND10 are unaffected by these inhibitors but can be recapitulated by overexpression of the SUMO isopeptidase SENP-1. Therefore, activation of SENP-1-like SUMO isopeptidase(s) during heat shock is not affected by these kinases. Thus, the release of ND10-associated proteins is not due to a general dispersal of nuclear domains but seems to be regulated by rapid desumolation during thermal stress and through the phosphorylation cascade of stress and mitogenic signaling pathways in the case of CdCl2. Whether the release of certain proteins had consequences was tested for heat-shock-protein transcription and synthesis. Release of Daxx correlated with Hsp25 suppression, suggesting that Daxx normally inhibits immediate Hsp25 production. Release of PML correlated with lower production of Hsp70. These results suggest that segregation or release of PML or Daxx have differential physiological relevance during the stress response. The fact that enzymatic activation of protein release or segregation after stress modifies the heat-shock response strengthens the concept of ND10 as a regulated depot of effector proteins.
Temperature‐Dependent Photonic Bandgap in a Self‐Assembled Hydrogen‐Bonded Liquid‐Crystalline Diblock Copolymer
Authors: Osuji C. , Chao C.‐Y. , Bita I. , Ober C.K. , Thomas E.L.
Published: December 2002

We take advantage of self‐assembly in a hierarchically structured, hybrid material to develop photonic bandgaps in the visible which may be systematically tuned by application of thermal or electric fields. Hydrogen bonding between a host polymer and a guest small molecule is used to augment the molecular weight of an appropriately selected coil–coil diblock copolymer to bring the microdomain structure onto the length scale needed for significant interaction with visible light. Further, the use of liquid‐crystal‐mesophase‐forming moieties as the guest hydrogen‐bonding units adds functionality to the system as the optical properties of the liquid‐crystalline domains can be modulated by external stimuli. We use hydrogen bonding to sequester varying amounts of imidazole terminated mesogens within the acid domains of a poly[styrene‐block‐poly‐(methacrylic acid)] (PS‐b‐MAA) diblock copolymer. The resulting PS‐b‐MAA/LC side‐group liquid‐crystalline diblock copolymer possesses a photonic bandgap in the green with the exact location and structure of the gap dependent on the composition of the system. Here, we discuss the structure and optical properties of these materials as a function of their composition and the response of the optical properties to temperature. Varying the order parameter of the LC domains by heating into the isotropic state changes the peak reflectivity by 40 nm, resulting in a color change from green to orange.
Polymer Gel Light‐Modulation Materials Imitating Pigment Cells
Authors: Akashi R. , Tsutsui H. , Komura A.
Published: December 2002

Novel light‐modulation materials composed of stimuli‐responsive gel particles with an added high concentration of colorants, which can modulate light due to an induced volume phase transition, have been obtained (see Figure). The light‐modulation mechanism and constitution of this material are similar to those of pigment cells existing in cephalopods, and the light absorption change is based on diffusion and aggregation of the colorants.
Fabrication of Chemically Patterned Surfaces Based on Template‐Directed Self‐Assembly
Authors: Lu N. , Gleiche M. , Zheng J. , Lenhert S. , Xu B. , Chi L. , Fuchs H.
Published: December 2002

Patterned surfaces with selective chemical activity are fabricated on Si/SiO2 surfaces using self‐assembly techniques and structured Langmuir–Blodgett monolayers as templates (see Figure). Molecules with different functional groups can be arranged to form regular patterns of lines with different surface free energies and chemical activities over macroscopic areas.
Highly Dispersive Micropatterns in Ion‐Exchanged Glass Formed by Ion Irradiation Through a Mask of Colloidal Particles
Authors: Strohhöfer C. , Hoogenboom J.P. , van Blaaderen A. , Polman A.
Published: December 2002

Refractive index gratings with hexagonal symmetry (see Figure) have been fabricated in ion‐exchanged borosilicate glass by ion irradiation through a mask of self‐organized silica colloidal particles. Light scattering measurements show diffraction rings and peaks belonging to hexagonal symmetry with a lattice constant approximately equal to the diameter of the particles in the colloidal mask.
Modification of Electronic Structures of a Carbon Nanotube by Hydrogen Functionalization
Authors: Kim K.S. , Bae D.J. , Kim J.R. , Park K.A. , Lim S.C. , Kim J.‐J. , Choi W.B. , Park C.Y. , Lee Y.H.
Published: December 2002

A rigorous method to engineer the electronic structure of carbon nanotubes from metallic to semiconducting is reported (see inside front cover). An intramolecular junction in carbon nanotube is fabricated, where half of the nanotube is masked by a silicon oxide thin film. Functionalization of the nanotube by atomic hydrogen leads to the formation of an intramolecular junction, resulting in clear rectifying behavior at room temperature. This represents an important step towards the practical realization of nanotube‐based nanotransistors.
Exchange Coupling and Remanence Enhancement in Nanocomposite Multilayer Magnets
Authors: Liu W. , Zhang Z.‐d. , Liu J.‐p. , Chen L.‐j. , He L.‐l. , Liu Y. , Sun X.‐k. , Sellmyer D.J.
Published: December 2002

Nanocomposite thin films (see Figure) that are prepared by sputtering and heat treatment demonstrate exchange coupling and remanence enhancement. A high remanence of Jr = 1.31 T and a maximum energy product of (B H)max = 203 kJ m–3 are achieved. These multilayer films consist of magnetically hard Nd2Fe14B‐type phase with a grain size of 40 nm and soft α‐Fe phase, existing in the form of continuous layers.
Super‐Hydrophobic Surfaces: From Natural to Artificial
Authors: Feng L. , Li S. , Li Y. , Li H. , Zhang L. , Zhai J. , Song Y. , Liu B. , Jiang L. , Zhu D.
Published: December 2002

Super‐hydrophobic surfaces, with a water contact angle (CA) greater than 150°, have attracted much interest for both fundamental research and practical applications. Recent studies on lotus and rice leaves reveal that a super‐hydrophobic surface with both a large CA and small sliding angle (α) needs the cooperation of micro‐ and nanostructures, and the arrangement of the microstructures on this surface can influence the way a water droplet tends to move. These results from the natural world provide a guide for constructing artificial super‐hydrophobic surfaces and designing surfaces with controllable wettability. Accordingly, super‐hydrophobic surfaces of polymer nanofibers and differently patterned aligned carbon nanotube (ACNT) films have been fabricated.
Light‐Emitting Silicon Nanocrystals from Laser Pyrolysis
Authors: Huisken F. , Ledoux G. , Guillois O. , Reynaud C.
Published: December 2002

Crystalline Si nanoparticles with diameters between 2.5 and 20 nm are prepared by CO2‐laser‐induced decomposition of silane in a gas flow reactor. A small portion of the products created in the reaction zone is extracted through a nozzle into a high‐acuum apparatus to form a freely propagating molecular beam of clusters and nanoparticles that can be deposited on suitable substrates. The strong visible photoluminescence (PL) of the Si nanocrystals is studied as a function of their size, and as a function of the time for which they are exposed to air. All observations can be explained on the basis of quantum confinement as the only origin of the PL. Chemical methods are exploited to modify the surface of the Si nanoparticles and to reduce their size, thus shifting their PL to shorter wavelengths. With this technique, the Si nanoparticles, collected in much larger quantities in the filter of the flow reactor, can be made strongly luminescent so that they may be used for various applications.
Acute myelogenous leukemia associated with extreme symptomatic thrombocytosis and chromosome 3q translocation: Case report and review of literature
Authors: Chang Victor T. , Aviv Hana , Howard Leslie M. , Padberg Frank
Published: December 2002

Acute leukemias with thrombocytosis have been recently linked with structural abnormalities of the short arm of chromosome 3. A 46‐year‐old man with a 2‐month history of recurrent transient ischemic attacks and abdominal pain developed an ischemic left foot and a gangrenous toe as his initial symptoms. Platelet count was 3.5 × 106/μL, and despite plateletpheresis, the patient required left‐leg amputation. Pathologic examination was remarkable for arterial thrombosis in the absence of atherosclerotic lesions. A diagnosis of acute myeloid leukemia with a novel translocation between chromosomes 3q21, 16, and 7 was made. Induction therapy was unsuccessful, and the patient died of overwhelming sepsis within 5 weeks of diagnosis. The striking features of this case were extreme symptomatic thrombocytosis, peripheral gangrene without atherosclerosis, and a novel three‐way chromosomal translocation involving chromosome 3q21. Am. J. Hematol. 72:20–26, 2003. © 2002 Wiley‐Liss, Inc.
Synthesis and in vitro Antimicrobial Evaluation of 5‐(1‐Methyl‐5‐nitro‐2‐imidazolyl)‐4H‐1, 2, 4‐triazoles
Authors: Shafiee Abbas , Sayadi Abolfazl , Roozbahani Marjan Hosseini , Foroumadi Alireza , Kamal Fatemeh
Published: December 2002

The increasing clinical importance of drug‐resistant pathogens has lent additional urgency to antimicrobial research. Various 5‐(1‐methyl‐5‐nitro‐2‐imidazolyl)‐4H‐1, 2, 4‐triazoles (4a—6f) were synthesized and tested in vitro for their antibacterial and antifungal activities. Compounds 4a and 4b exhibited significant effects against Bacillus subtilis at MIC ranges of 0.5—1 μg/mL and moderate effects against Staphylococcus aureus.
Fine Tuning of Photophysical Properties of meso–meso‐Linked ZnII–Diporphyrins by Dihedral Angle Control
Authors: Yoshida Naoya , Ishizuka Tomoya , Osuka Atsuhiro , Jeong Dae Hong , Cho Hyun Sun , Kim Dongho , Matsuzaki Yoichi , Nogami Atsushi , Tanaka Kazuyoshi
Published: December 2002

A series of meso–meso‐linked diporphyrins Sn strapped with a dioxymethylene group of various length were synthesized by intramolecular AgI‐promoted coupling of dioxymethylene‐bridged diporphyrins Bn, for n=10, 8, 6, 5, 4, 3, 2, and 1. Shortening of the strap length causes a gradual decrease in the dihedral angle between the porphyrins and increasing distortion of porphyrin ring, as suggested by MM2 calculations and 1H NMR studies. This trend has been also suggested by X‐ray crystallographic studies on the corresponding CuII complexes of nonstrapped diporphyrin 2 Cu, and strapped diporphyrins S8Cu, S4Cu, and S2Cu. The absorption spectrum of relatively unconstrained diporphyrins S10 strapped with a long chain exhibits split Soret bands at 414 and 447 nm and weak Q(0,0)‐ and prominent Q(1,0)‐bands, both of which are similar to those of nonstrapped diporphyrin 2. Shortening of the strap length causes systematic changes in the absorption spectra, in which the intensities of the split Soret bands decrease, the absorption bands at about 400 nm and > 460 nm increase in intensity, and a prominent one‐band feature of a Q‐band is changed to a distinct two‐band feature with concurrent progressive red‐shifts of the lowest Q(0,0)‐band. The fluorescence spectra also exhibit systematic changes, roughly reflecting the changes of the absorption spectra. The strapped diporphyrins Sn are all chiral and have been separated into enantiomers over a chiral column. The CD spectra of the optically active Sn display two Cotton effects at 430–450 and at about 400 nm with the opposite signs. The latter effect can be explained in terms of oblique arrangement of m⊥1 and m⊥2 dipole moments, while the former effect cannot be accunted for within a framework of the exction coupling theory. The resonance Raman (RR) spectra taken for excitation at 457.9 nm are variable among Sn, while the RR spectra taken for excitation at 488.0 nm are constant throughout the Sn series. These photophysical properties can be explained in terms of INDO/S‐SCI calculations, which have revealed charge transfer (CT) transitions accidentally located close in energy to the excitonic Soret transitions. This feature arises from a close proximity of the two porphyrins in meso–meso‐linked diporphyrins. In addition to the gradual red‐shift of the exciton split Soret band, the calculations predict that the high‐energy absorption band at about 400 nm, the lower energy Cotton effect, and the RR spectra taken for excitation at 457.9 nm are due to the CT states which are intensified upon a decrease in the dihedral angle.
Synthesis and Formation Mechanism of Manganese Dioxide Nanowires/Nanorods
Authors: Wang Xun , Li Yadong
Published: December 2002

α‐, β‐, γ‐, and δ‐MnO2 single‐crystal nanowires/nanorods with different aspect ratios have been successfully prepared by a common hydrothermal method based on the redox reactions of MnO4− and/or Mn2+. The influences of oxidant, temperature, and inorganic cation (NH4+ and K+) template concentrations on the morphology and crystallographic forms of the final products are discussed in this paper. It is interesting to find that all the MnO2 one‐dimensional nanostructures have a similar formation process: δ‐MnO2, which has a layer structure, serves as an important intermediate to other forms of MnO2, and is believed to be responsible for the initial formation of MnO2 one‐dimensional nanostructures. A rolling mechanism has been proposed based on the results of the series of TEM images and XRD patterns of the intermediate.
The Molecular Structure of Different Species of Cuprous Chloride from Gas‐Phase Electron Diffraction and Quantum Chemical Calculations
Authors: Hargittai Magdolna , Schwerdtfeger Peter , Réffy Balázs , Brown Reuben
Published: December 2002

The molecular geometry of gaseous cuprous chloride oligomers was determined by gas‐phase electron diffraction at two different temperatures. Quantum chemical calculations were also performed for CunCln(n=1–4) molecules. A complex vapor composition was found in both experiments. Molecules of Cu3Cl3and Cu4Cl4were present at the lower temperature (689 K), while dimeric molecules (Cu2Cl2) were found in addition to the trimers and tetramers at the higher temperature (1333 K). All CunClnspecies were found to have planar rings by both experiment and computation. The bond lengths from electron diffraction (rg) at 689 K are 2.166±0.008 Å and 2.141±0.008 Å and the Cu‐Cl‐Cu bond angles are 73.9±0.6° and 88.0±0.6° for the trimer and the tetramer, respectively. At 1333 K the bond lengths are 2.254±0.011 Å, 2.180±0.011 Å, and 2.155±0.011 Å, and the CuClCu bond angles 67.3±1.1°, 74.4±1.1°, and 83.6±1.1° for the dimer, trimer, and tetramer, respectively.
Recycling of Homogeneous Hydrogenation Catalysts by Dialysis Coupled Catalysis
Authors: De Smet Koen , Pleysier Annick , Vankelecom Ivo F. J. , Jacobs Pierre A.
Published: December 2002

Although transition‐metal complexes are very attractive as homogeneous catalysts in fine chemistry, their high prices often limit their applications. A means to recycle those catalysts would solve this problem and would simultaneously facilitate the downstream purification of the product. This is now realized in a new concept in which homogeneous catalysis is coupled to dialysis. The advantages of homogeneous catalysis (off‐the‐shelf catalysts, high activities and selectivities) are thus combined with those of heterogeneous catalysis (easy catalyst separation from product solution, reuse of catalyst, and possibility for continuous operation). Since the heart of the process is the membrane, self‐prepared membranes were preferred as they allow a better control and understanding of the separation characteristics. Rhodamine B was used as a probe molecule to define the working conditions of the membrane. The concept is proven to work for two relevant chiral reactions: a hydrogenation with Ru–BINAP and a hydrogen transfer reaction with Ru–TsDPEN [BINAP=(1,1′‐binaphthalene)‐2,2′‐diylbis(diphenylphosphine); TsDPEN= tosyl‐N,N′‐diphenyl‐1,2‐ethanediamine].
New Mechanistic Insights into the Iridium–Phosphanooxazoline‐Catalyzed Hydrogenation of Unfunctionalized Olefins: A DFT and Kinetic Study
Authors: Brandt Peter , Hedberg Christian , Andersson Pher G.
Published: December 2002

The reaction mechanism of the iridium–phosphanooxazoline‐catalyzed hydrogenation of unfunctionalized olefins has been studied by means of density functional theory calculations (B3LYP) and kinetic experiments. The calculations suggest that the reaction involves an unexpected IrIII–IrV catalytic cycle facilitated by coordination of a second equivalent of dihydrogen. Thus, in the rate‐determining migratory insertion of the substrate alkene into an iridium–hydride bond, simultaneous oxidative addition of the bound dihydrogen occurs. The kinetic data shows that the reaction is first order with respect to hydrogen pressure. This is interpreted in terms of an endergonic coordination of this second equivalent of dihydrogen, although a rate‐determining step, in which coordinated solvent is replaced by dihydrogen, could not be ruled out. Furthermore, the reaction was found to be zeroth order with respect to the alkene concentration. This correlates well with the calculated exothermicity of substrate coordination, and the catalyst is thus believed to coordinate an alkene in the resting state. On the basis of the proposed catalytic cycle, calculations were performed on a full‐sized system with 88 atoms to assess the appropriateness of the model calculations. These calculations were also used to explain the enantioselectivity exerted by the catalyst.
Raman Spectroscopy—A Prospective Tool in the Life Sciences
Authors: Petry Renate , Schmitt Michael , Popp Jürgen
Published: December 2002

Although the physics of Raman spectroscopy and its application to purely chemical problems is long established, it offers a noninvasive, nondestructive, and water‐insensitive probe to problems in the life sciences. Starting from the principles of Raman spectroscopy, its advantages, and methods for signal enhancement, the bulk of the review highlights recent applications. Structural investigations of a hormone receptor, testing the biocompatibility of dental implants, probing soil components and plant tissue alkaloids, and localization of single bacteria are just four problems in which Raman spectroscopy offers a solution or complements existing methods.
Molecular Logic Circuits
Authors: Balzani Vincenzo , Credi Alberto , Venturi Margherita
Published: December 2002

Miniaturization has been an essential ingredient in the outstanding progress of information technology over the past fifty years. The next, perhaps ultimate, limit of miniaturization is that of molecules, which are the smallest entities with definite size, shape, and properties. Recently, great effort has been devoted to design and investigate molecular‐level systems that are capable of transferring, processing, and storing information in binary form. Some of these nanoscale devices can, in fact, perform logic operations of remarkable complexity. This research—although far from being transferred into technology—is attracting interest, as the nanometer realm seems to be out of reach for the “top‐down” techniques currently available to microelectronics industry. Moreover, such studies introduce new concepts in the “old” field of chemistry and stimulate the ingenuity of researchers engaged in the “bottom‐up” approach to nanotechnology.
On the Dissociation of Aromatic Radical Anions in Solution
Authors: Laage Damien , Burghardt Irène , Sommerfeld Thomas , Hynes James T.
Published: December 2002

A new theoretical formulation is given for the reaction rate and path for the important reaction class of aromatic radical anion dissociation in solution [ArX]−.→Ar.+X−, and is illustrated for the case of the cyanochlorobenzene radical anion [CNΦCl]−. in dimethylformamide. Among the theory's novel features is the inclusion of the conical intersection aspect of this ground electronic state problem, which is key in allowing the reaction to occur and which has a significant impact on the reaction barrier height. Reasonable agreement with the experimental rate is found.
Correlation of Molecular Assembly and Interactions in Crystals and Langmuir–Blodgett Films of N‐(2,4‐dinitrophenyl)‐n‐octadecylamine
Authors: Sharma Sonika , Radhakrishnan T. P.
Published: December 2002

Correlation of molecular organization in crystals and in ultrathin films is of fundamental interest in the design of molecular materials based on thin films. We have chosen as a test case, N‐(2,4‐dinitrophenyl)‐n‐octadecylamine (DNPOA), a potential candidate for the fabrication of Langmuir–Blodgett (LB) films for quadratic nonlinear optical applications. Like several other 4‐nitroaniline derivatives, DNPOA does not form stable monolayers at the air–water interface. This has precluded investigations of their organization in LB films. We have stabilized composite Langmuir films of DNPOA with the phospholipid molecule DSPC and fabricated their LB films. Successful growth of single crystals of DNPOA allowed structure determination and detailed analysis of molecular associations in the solid state. Electronic absorption spectra of DNPOA in solution, in the solid state and in the LB film are investigated. Modeling of the various spectral signatures by semiempirical computations on molecular clusters extracted from the crystal lattice provides insight into the correlation between the molecular organization in crystals and in LB films.