bluuebunny/crossref_metadata_2025 huggingface dataset:
Heparin-binding properties of selenium-containing thioredoxin reductase from HeLa cells and human lung adenocarcinoma cells
Authors: Liu Song-Yuan , Stadtman Thressa C.
Published: July 2002

Mammalian selenocysteine-containing thioredoxin reductase (TR)
isolated from HeLa cells and from human lung adenocarcinoma cells was
separated into two major enzyme species by heparin-agarose affinity
chromatography. The low-affinity enzyme forms that were not retained on
heparin agarose showed strong crossreactivity in immunoblot assays with
anti-rat liver TR polyclonal antibodies, whereas the high-affinity
enzyme forms that were retained by the heparin column were not
detected. Both low and high heparin-affinity enzyme forms contained
FAD, were indistinguishable on SDS/PAGE analysis, and exhibited
similar catalytic activities in the NADPH-dependent DTNB
[5,5′-dithiobis(2-nitrobenzoate)] assay. The C-terminal amino acid
sequences of
75
Se-labeled tryptic peptides from lung
adenocarcinoma low- and high heparin-affinity enzyme forms were
identical to the predicted C-terminal sequence of human placental TR.
These two determined peptide sequences were
-Ser-Gly-Ala-Ser-Ile-Leu-Gln-Ala-Gly-Cys-Secys-(Gly). Occurrence of the
Se-carboxymethyl derivative of radioactive selenocysteine in the
position corresponding to TGA in the gene confirmed that UGA is
translated as selenocysteine. The presence of cysteine followed by a
reactive selenocysteine residue in this C-terminal region of the
protein may explain some of the unusual properties of the mammalian
TRs.
The role of phenylalanine in structure–function relationships of phenylalanine hydroxylase revealed by radiation target analysis
Authors: Davis Michael D. , Parniak Michael A. , Kaufman Seymour , Kempner Ellis
Published: July 2002

The activity of rat liver phenylalanine hydroxylase (PAH; phenylalanine 4-monooxygenase, EC
1.14.16.1
) is regulated by interaction with its substrate, phenylalanine, and its coenzyme, BH
4
[tetrahydrobiopterin (6
R
-dihydroxypropyl-
l
-erythro-5,6,7,8-tetrahydropterin)]. The structural changes accompanying these interactions have been studied by radiation target analysis. PAH purified from rat liver was incubated with 2 mM phenylalanine to achieve complete activation of the enzyme. Frozen samples were irradiated with various doses of high energy electrons; samples were subsequently thawed, and several surviving properties of the enzyme were determined. Each parameter decreased as a single exponential function of radiation dose. Radiation target analysis of enzymatic activity yielded a dimeric target size. Similar radiation effects on subunit monomers and on tetrameric structure were observed. Together with results from unactivated enzyme, these data show that phenylalanine increases the interactions between the subunits in a dimer and weakens the interactions between dimers in a tetramer. These alterations prevent the natural cofactor, a tetrahydrobiopterin, from exerting a negative effect on activity.
ELL2, a new member of an ELL family of RNA polymerase II elongation factors
Authors: Shilatifard Ali , Duan D. Roxanne , Haque Dewan , Florence Charles , Schubach William H. , Conaway Joan Weliky , Conaway Ronald C.
Published: July 2002

We recently isolated an RNA polymerase II elongation factor from rat liver nuclei and found it to be homologous to the product of the human
ELL
gene, a frequent target for translocations in acute myeloid leukemia. To further our understanding of the possible role(s) of ELL in transcriptional regulation and human disease, we initiated a search for ELL-related proteins. In this report we describe molecular cloning, expression, and characterization of human ELL2, a novel RNA polymerase II elongation factor 49% identical and 66% similar to ELL. Mechanistic studies indicate that ELL2 and ELL possess similar transcriptional activities. Structure–function studies localize the ELL2 elongation activation domain to an ELL2 N-terminal region that is highly homologous to ELL. Finally, Northern blot analysis reveals that the ELL2 and ELL genes are transcribed in many of the same tissues, but that the ratio of their transcripts exhibits tissue-to-tissue variation, raising the possibility that ELL2 and ELL may not perform completely general functions, but, instead, may perform gene- or tissue-specific functions.
A permeabilized cell system that assembles filamentous bacteriophage
Authors: Feng Jian-nong , Russel Marjorie , Model Peter
Published: July 2002

A permeabilized cell system has been developed that is capable of assembling filamentous phage only upon addition of exogenous thioredoxin. The
in vitro
system exhibits the same component requirements seen
in vivo
: functional thioredoxin, an intact packaging signal in the substrate DNA, and the assembly protein, pIV. This crude
in vitro
system is insensitive to inhibitors of protein or DNA synthesis, demonstrating that particle assembly uses components that had accumulated before cell permeabilization. The temporal separation of the synthetic period, during which phage proteins and DNA accumulate, from the assembly period enabled us to examine the energy requirement for assembly. We show here that ATP hydrolysis is required for filamentous phage assembly and that the proton motive force is also important.
A lightweight universe?
Authors: Bahcall Neta A. , Fan Xiaohui
Published: July 2002

How much matter is there in the universe? Does the universe have the critical density needed to stop its expansion, or is the universe underweight and destined to expand forever? We show that several independent measures, especially those utilizing the largest bound systems known—clusters of galaxies—all indicate that the mass-density of the universe is insufficient to halt the expansion. A promising new method, the evolution of the number density of clusters with time, provides the most powerful indication so far that the universe has a subcritical density. We show that different techniques reveal a consistent picture of a lightweight universe with only ∼20–30% of the critical density. Thus, the universe may expand forever.
Phosphorylation and activation of cAMP-dependent protein kinase by phosphoinositide-dependent protein kinase
Authors: Cheng Xiaodong , Ma Yuliang , Moore Michael , Hemmings Brian A. , Taylor Susan S.
Published: July 2002

Although phosphorylation of Thr-197 in the activation loop of the catalytic subunit of cAMP-dependent protein kinase (PKA) is an essential step for its proper biological function, the kinase responsible for this reaction
in vivo
has remained elusive. Using nonphosphorylated recombinant catalytic subunit as a substrate, we have shown that the phosphoinositide-dependent protein kinase, PDK1, expressed in 293 cells, phosphorylates and activates the catalytic subunit of PKA. The phosphorylation of PKA by PDK1 is rapid and is insensitive to PKI, the highly specific heat-stable protein kinase inhibitor. A mutant form of the catalytic subunit where Thr-197 was replaced with Asp was not a substrate for PDK1. In addition, phosphorylation of the catalytic subunit can be monitored immunochemically by using antibodies that recognize Thr-197 phosphorylated enzyme but not unphosphorylated enzyme or the Thr197Asp mutant. PDK1, or one of its homologs, is thus a likely candidate for the
in vivo
PKA kinase that phosphorylates Thr-197. This finding opens a new dimension in our thinking about this ubiquitous protein kinase and how it is regulated in the cell.
Plant–pathogen microevolution: Molecular basis for the origin of a fungal disease in maize
Authors: Multani D. S. , Meeley R. B. , Paterson A. H. , Gray J. , Briggs S. P. , Johal G. S.
Published: July 2002

A new and severe disease of maize caused by a previously unknown fungal pathogen,
Cochliobolus carbonum
race 1, was first described in 1938. The molecular events that led to the sudden appearance of this disease are described in this paper. Resistance to
C. carbonum
race 1 was found to be widespread in maize and is conferred by a pair of unlinked duplicate genes,
Hm1
and
Hm2
. Here, we demonstrate that resistance is the wild-type condition in maize. Two events, a transposon insertion in
Hm1
and a deletion in
Hm2
, led to the loss of resistance, resulting in the origin of a new disease. None of the other plant species tested is susceptible to
C. carbonum
race 1, and they all possess candidate genes with high homology to
Hm1
and
Hm2
. In sorghum and rice, these homologs map to two chromosomal regions that are syntenic with the maize
Hm1
and
Hm2
loci, indicating that they are related to the maize genes by vertical descent. These results suggest that the
Hm
-encoded resistance is of ancient origin and probably is conserved in all grasses.
Compartmentalized expression of two structurally and functionally distinct 4-coumarate:CoA ligase genes in aspen (
Populus tremuloides
)
Authors: Hu Wen-Jing , Kawaoka Akiyoshi , Tsai Chung-Jui , Lung Jrhau , Osakabe Keishi , Ebinuma Hiroyasu , Chiang Vincent L.
Published: July 2002

4-Coumarate:CoA ligases (4CLs, EC
6.2.1.12
) are a group of enzymes necessary for maintaining a continuous metabolic flux for the biosynthesis of plant phenylpropanoids, such as lignin and flavonoids, that are essential to the survival of plants. So far, various biochemical and molecular studies of plant 4CLs seem to suggest that 4CL isoforms in plants are functionally indistinguishable in mediating the biosynthesis of these phenolics. However, we have discovered two functionally and structurally distinct 4CL genes,
Pt4CL1
and
Pt4CL2
(63% protein sequence identity), that are differentially expressed in aspen (
Populus tremuloides
). The
Escherichia coli
-expressed and purified Pt4CL1 and Pt4CL2 proteins exhibited highly divergent substrate preference as well as specificity that reveal the association of Pt4CL1 with the biosynthesis of guaiacyl–syringyl lignin and the involvement of Pt4CL2 with other phenylpropanoid formation. Northern hybridization analysis demonstrated that
Pt4CL1
mRNA is specifically expressed in lignifying xylem tissues and
Pt4CL2
mRNA is specifically expressed in epidermal layers in the stem and the leaf, consistent with the promoter activities of
Pt4CL1
and
Pt4CL2
genes based on the heterologous promoter-β-glucouronidase fusion analysis. Thus, the expression of
Pt4CL1
and
Pt4CL2
genes is compartmentalized to regulate the differential formation of phenylpropanoids that confer different physiological functions in aspen;
Pt4CL1
is devoted to lignin biosynthesis in developing xylem tissues, whereas
Pt4CL2
is involved in the biosynthesis of other phenolics, such as flavonoids, in epidermal cells.
Auxin-induced K
+
channel expression represents an essential step in coleoptile growth and gravitropism
Authors: Philippar Katrin , Fuchs Ines , Lüthen Hartwig , Hoth Stefan , Bauer Claudia S. , Haga Ken , Thiel Gerhard , Ljung Karin , Sandberg Göran , Böttger Michael , Becker Dirk , Hedrich Rainer
Published: July 2002

Auxin-induced growth of coleoptiles depends on the presence of potassium and is suppressed by K
+
channel blockers. To evaluate the role of K
+
channels in auxin-mediated growth, we isolated and functionally expressed ZMK1 and ZMK2 (
Zea mays
K
+
channel 1 and 2), two potassium channels from maize coleoptiles. In growth experiments, the time course of auxin-induced expression of
ZMK1
coincided with the kinetics of coleoptile elongation. Upon gravistimulation of maize seedlings,
ZMK1
expression followed the gravitropic-induced auxin redistribution. K
+
channel expression increased even before a bending of the coleoptile was observed. The transcript level of
ZMK2
, expressed in vascular tissue, was not affected by auxin. In patch-clamp studies on coleoptile protoplasts, auxin increased K
+
channel density while leaving channel properties unaffected. Thus, we conclude that coleoptile growth depends on the transcriptional up-regulation of ZMK1, an inwardly rectifying K
+
channel expressed in the nonvascular tissue of this organ.
Differential adsorption of nucleic acid bases: Relevance to the origin of life
Authors: Sowerby Stephen J. , Cohn Corey A. , Heckl Wolfgang M. , Holm Nils G.
Published: July 2002

The adsorption of organic molecules onto the surfaces of inorganic
solids has long been considered a process relevant to the origin of
life. We have determined the equilibrium adsorption isotherms for the
nucleic acid purine and pyrimidine bases dissolved in water on the
surface of crystalline graphite. The markedly different adsorption
behavior of the bases describes an elutropic series: guanine >
adenine > hypoxanthine > thymine > cytosine >
uracil. We propose that such differential properties were relevant to
the prebiotic chemistry of the bases and may have influenced the
composition of the primordial genetic architecture.
Ultra-Nationalists in Russia at the Onset of Putin's Rule
Authors: Verkhovsky Alexander
Published: July 2002

Ten years ago, the destruction of totalitarian Soviet society led many to fear that in a country with little experience of democracy, another totalitarian regime would supersede the old one. But which regime, and in what form? The national conflicts that accompanied the disintegration of the Soviet Union suggested a feasible answer right away, namely, a national dictatorship of the fascist sort, composed of nationalistic ideology and a totalitarian social structure. No such dictatorship has occurred in contemporary Russia and none is anticipated in the near future. The “Weimar Russia” scenario, which the political science expert Alexander Ianov developed in such great detail, has not materialized.
Overview of (1→3)‐β‐D‐glucan immunobiology
Authors: Williams David L.
Published: July 2002

Glucans are (1→3)‐β‐D‐glucose polymers that are found in the cell wall of fungi, bacteria and plants. Glucans are known to stim ulate humoral and cell‐mediated immunity in humans and animals. In addition to the potent immune stimulatory effects of (1→3)‐β‐D‐glucans, there are a number of toxicological effects associated with exposure to the water‐insoluble, microparticulate form of the polymer. Recent investigations have suggested a potential role for (1→3)‐β‐D‐glucans in inhalational toxicity. Specifically, (1→3)‐β‐D‐glucans have been implicated in the symptomatology associated with ‘sick building’ syndrome. The mechanisms by which
(1→3)‐β‐D‐glucans mediate immune stimulation and, perhaps, toxicity are currently under investigation. It is now established that (1→3)‐β‐D‐glucans are recognized by macrophages and, perhaps, neutrophils and natural killer cells via a (1→3)‐β‐glucan specific receptor. Following receptor binding, glucan modulates macrophage cytokine expression. Here we review the chemistry, immunobiology and toxicity of (1→3)‐β‐D‐glucans and how it may relate to effects caused by inhalation.
Myosin Light Chain Kinase as a Multifunctional Regulatory Protein of Smooth Muscle Contraction
Authors: Gao Ying , Ye Li‐Hong , Kishi Hiroko , Okagaki Tsuyoshi , Samizo Koichi , Nakamura Akio , Kohama Kazuhiro
Published: July 2002

Myosin light chain kinase (MLCK) is a regulatory protein for smooth muscle contraction, which acts by phosphorylating 20‐kDa myosin light chain (MLC20) to activate the myosin ATPase activity. Although this mode of action is well‐established, there are numerous reports of smooth muscle contraction that is not associated with MLC20 phosphorylation. The kinase activity for the phosphorylation is localized at the central part of MLCK, which is also furnished with actin‐binding activity at its N terminal and myosin‐binding activity at its C terminal. This article overviews as to how such multifunctional properties of MLCK modify the actin‐myosin interaction and presents our observations that the phosphorylation is not obligatory in induction of smooth muscle contraction.
Regulation of Actin Polymerization in Cell-free Systems by GTPγS and Cdc42
Authors: Zigmond Sally H. , Joyce Michael , Borleis Jane , Bokoch Gary M. , Devreotes Peter N.
Published: July 2002

We have established a cell-free system to investigate pathways that regulate actin polymerization. Addition of GTPγS to lysates of polymorphonuclear leukocytes (PMNs) or Dictyostelium discoideum amoeba induced formation of filamentous actin. The GTPγS appeared to act via a small G-protein, since it was active in lysates ofD. discoideum mutants missing either the α2- or β-subunit of the heterotrimeric G-protein required for chemoattractant-induced actin polymerization in living cells. Furthermore, recombinant Cdc42, but not Rho or Rac, induced polymerization in the cell-free system. The Cdc42-induced increase in filamentous actin required GTPγS binding and was inhibited by a fragment of the enzyme PAK1 that binds Cdc42.

In a high speed supernatant, GTPγS alone was ineffective, but GTPγS-loaded Cdc42 induced actin polymerization, suggesting that the response was limited by guanine nucleotide exchange. Stimulating exchange by chelating magnesium, by adding acidic phospholipids, or by adding the exchange factors Cdc24 or Dbl restored the ability of GTPγS to induce polymerization. The stimulation of actin polymerization did not correlate with PIP2 synthesis.
Thrombopoietin-induced Polyploidization of Bone Marrow Megakaryocytes Is Due to a Unique Regulatory Mechanism in Late Mitosis
Authors: Nagata Yuka , Muro Yoshinao , Todokoro Kazuo
Published: July 2002

Megakaryocytes undergo a unique differentiation program, becoming polyploid through repeated cycles of DNA synthesis without concomitant cell division. However, the mechanism underlying this polyploidization remains totally unknown. It has been postulated that polyploidization is due to a skipping of mitosis after each round of DNA replication. We carried out immunohistochemical studies on mouse bone marrow megakaryocytes during thrombopoietin- induced polyploidization and found that during this process megakaryocytes indeed enter mitosis and progress through normal prophase, prometaphase, metaphase, and up to anaphase A, but not to anaphase B, telophase, or cytokinesis. It was clearly observed that multiple spindle poles were formed as the polyploid megakaryocytes entered mitosis; the nuclear membrane broke down during prophase; the sister chromatids were aligned on a multifaced plate, and the centrosomes were symmetrically located on either side of each face of the plate at metaphase; and a set of sister chromatids moved into the multiple centrosomes during anaphase A. We further noted that the pair of spindle poles in anaphase were located in close proximity to each other, probably because of the lack of outward movement of spindle poles during anaphase B. Thus, the reassembling nuclear envelope may enclose all the sister chromatids in a single nucleus at anaphase and then skip telophase and cytokinesis. These observations clearly indicate that polyploidization of megakaryocytes is not simply due to a skipping of mitosis, and that the megakaryocytes must have a unique regulatory mechanism in anaphase, e.g., factors regulating anaphase such as microtubule motor proteins might be involved in this polyploidization process.
The Transcriptional Corepressor NAB2 Inhibits NGF-induced Differentiation of PC12 Cells
Authors: Qu Zhican , Wolfraim Lawrence A. , Svaren John , Ehrengruber Markus U. , Davidson Norman , Milbrandt Jeffrey
Published: July 2002

The PC12 pheochromocytoma cell line responds to NGF by undergoing growth arrest and proceeding to differentiate toward a neuronal phenotype. Among the early genetic events triggered by NGF in PC12 cells are the rapid activation of the zinc finger transcription factor Egr1/NGFI-A, and a slightly delayed induction of NAB2, a corepressor that inhibits Egr1 transcriptional activity. We found that stably transfected PC12 cells expressing high levels of NAB2 do not differentiate, but rather continue to proliferate in response to NGF. Inhibition of PC12 differentiation by NAB2 overexpression was confirmed using two additional experimental approaches, transient transfection, and adenoviral infection. Early events in the NGF signaling cascade, such as activation of MAP kinase and induction of immediate-early genes, were unaltered in the NAB2-overexpressing PC12 cell lines. However, induction of delayed NGF response genes such as TGF-β1 and MMP-3 was inhibited. Furthermore, NAB2 overexpression led to downregulation of p21WAF1, a molecule previously shown to play a pivotal role in the ability of PC12 cells to undergo growth arrest and commit to differentiation in response to NGF. Cotransfection with p21WAF1 restored the ability of NAB2-overexpressing PC12 cells to differentiate in response to NGF.
Induction of Apoptosis of Metastatic Mammary Carcinoma Cells In Vivo by Disruption of Tumor Cell Surface CD44 Function
Authors: Yu Qin , Toole Bryan P. , Stamenkovic Ivan
Published: July 2002

To understand how the hyaluronan receptor CD44 regulates tumor metastasis, the murine mammary carcinoma TA3/St, which constitutively expresses cell surface CD44, was transfected with cDNAs encoding soluble isoforms of CD44 and the transfectants (TA3sCD44) were compared with parental cells (transfected with expression vector only) for growth in vivo and in vitro. Local release of soluble CD44 by the transfectants inhibited the ability of endogenous cell surface CD44 to bind and internalize hyaluronan and to mediate TA3 cell invasion of hyaluronan-producing cell monolayers. Mice intravenously injected with parental TA3/St cells developed massive pulmonary metastases within 21–28 d, whereas animals injected with TA3sCD44 cells developed few or no tumors. Tracing of labeled parental and transfectant tumor cells revealed that both cell types initially adhered to pulmonary endothelium and penetrated the interstitial stroma. However, although parental cells were dividing and forming clusters within lung tissue 48 h following injection, >80% of TA3sCD44 cells underwent apoptosis. Although sCD44 transfectants displayed a marked reduction in their ability to internalize and degrade hyaluronan, they elicited abundant local hyaluronan production within invaded lung tissue, comparable to that induced by parental cells. These observations provide direct evidence that cell surface CD44 function promotes tumor cell survival in invaded tissue and that its suppression can induce apoptosis of the invading tumor cells, possibly as a result of impairing their ability to penetrate the host tissue hyaluronan barrier.
Eliminating a Region of Respiratory Syncytial Virus Attachment Protein Allows Induction of Protective Immunity without Vaccine-enhanced Lung Eosinophilia
Authors: Sparer Tim E. , Matthews Stephen , Hussell Tracy , Rae Aaron J. , Garcia-Barreno Blanca , Melero Jose A. , Openshaw Peter J.M.
Published: July 2002

In a murine model of respiratory syncytial virus disease, prior sensitization to the attachment glycoprotein (G) leads to pulmonary eosinophilia and enhanced illness. Three different approaches were taken to dissect the region of G responsible for enhanced disease and protection against challenge. First, mutant viruses, containing frameshifts that altered the COOH terminus of the G protein, were used to challenge mice sensitized by scarification with recombinant vaccinia virus (rVV) expressing wild-type G. Second, cDNA expressing these mutated G proteins were expressed by rVV and used to vaccinate mice before challenge with wild-type respiratory syncytial virus (RSV). These studies identified residues 193–205 to be responsible for G-induced weight loss and lung eosinophilia and showed that this region was not was not necessary for induction of protective immunity. Third, mice were sensitized using an rVV that expressed only amino acids 124–203 of the G protein. Upon RSV challenge, mice sensitized with this rVV developed enhanced weight loss and eosinophilia. This is the first time that a region within RSV (amino acids 193–203) has been shown to be responsible for induction of lung eosinophilia and disease enhancement. Moreover, we now show that it is possible to induce protective immunity with an altered G protein without inducing a pathological response.
Neutrophil Granulocyte–committed Cells Can Be Driven to Acquire Dendritic Cell Characteristics
Authors: Oehler Leopold , Majdic Otto , Pickl Winfried F. , Stöckl Johannes , Riedl Elisabeth , Drach Johannes , Rappersberger Klemens , Geissler Klaus , Knapp Walter
Published: July 2002

Polymorphonuclear granulocytes (PMNs) are thought to fulfill their role in host defense primarily via phagocytosis and release of cytotoxic compounds and to be inefficient in antigen presentation and stimulation of specific T cells. Dendritic cells (DCs), in contrast, are potent antigen-presenting cells with the unique capacity to initiate primary immune responses. We demonstrate here that highly purified lactoferrin-positive immediate precursors of end-stage neutrophilic PMN (PMNp) can be reverted in their functional maturation program and driven to acquire characteristic DC features. Upon culture with the cytokine combination granulocyte/macrophage colony-stimulating factor plus interleukin 4 plus tumor necrosis factor α, they develop DC morphology and acquire molecular features characteristic for DCs. These molecular changes include neo-expression of the DC-associated surface molecules cluster of differentiation (CD)1a, CD1b, CD1c, human leukocyte antigen (HLA)-DR, HLA-DQ, CD80, CD86, CD40, CD54, and CD5, and downregulation of CD15 and CD65s. Additional stimulation with CD40 ligand induces also expression of CD83 and upregulates CD80, CD86, and HLA-DR. The neutrophil-derived DCs are potent T cell stimulators in allogeneic, as well as autologous, mixed lymphocyte reactions (MLRs), whereas freshly isolated neutrophils are completely unable to do so. In addition, neutrophil-derived DCs are at least 10,000 times more efficient in presenting soluble antigen to autologous T cells when compared to freshly isolated monocytes. Also, in functional terms, these neutrophil-derived DCs thus closely resemble “classical” DC populations.
Identification of a Human Enterocyte Lipoxin A4 Receptor That Is Regulated by Interleukin (IL)-13 and Interferon γ and Inhibits Tumor Necrosis Factor α–induced IL-8 Release
Authors: Gronert Karsten , Gewirtz Andrew , Madara James L. , Serhan Charles N.
Published: July 2002

Epithelial cells of the alimentary tract play a central role in mucosal immunophysiology. Pathogens and/or agonists that interact with mucosal surfaces often elicit epithelial responses that upregulate inflammation. Therefore, it was of interest to explore potential epithelial targeted antiinflammatory signals. Here we identified and sequenced a human enterocyte lipoxin (LX) A4 [5(S),6(R),15(S)-trihydroxy-7,9,13-trans-11-cis eicosatetraenoic acid] receptor, and demonstrate that transcription of this receptor was controlled by cytokines, of which lymphocyte-derived interleukin (IL)-13 and interferon γ were the most potent. When lipoxins and LXA4 stable analogs were evaluated for enterocyte functional as well as immune responses, lipoxins sharply inhibited TNF-α–induced IL-8 release but did not alter either barrier function or agonist-stimulated chloride secretion. 15R/S-methyl-LXA4 and 16-phenoxy-LXA4 each attenuated (IC50 ∼10 nM) IL-8 release. Cyclooxygenase (COX) II is emerging as an important component in wound healing and proliferation in intestinal epithelia and when acetylated by acetylsalicylic acid (aspirin) initiates the biosynthesis of a LXA4 receptor ligand. We therefore determined whether colonic cell lines (HT-29 Cl.19A, Caco-2, or T84) express the COX II isozyme. Results for RT-PCR and Western blot analysis showed that COX I as well as an IL-1β– and TNF-α–inducible COX II are expressed in HT-29 Cl.19A. In addition, aspirin-treated enterocytes generated 15R-HETE, a precursor of 15-epi-LXA4 biosynthesis, whose potent bioactions were mimicked by the stable analog 15R/S-methyl-LXA4. Taken together, these results identify an endogenous pathway for downregulating mucosal inflammatory events and suggest a potential therapeutic benefit for LXA4 stable analogs.
Mice Lacking Expression of the Chemokines Ccl21-Ser and Ccl19 (plt Mice) Demonstrate Delayed but Enhanced T Cell Immune Responses
Authors: Mori Shigeyuki , Nakano Hideki , Aritomi Kentaro , Wang Chrong-Reen , Gunn Michael D. , Kakiuchi Terutaka
Published: July 2002

The paucity of lymph node T cells (plt) mutation leads to a loss of CCL21 and CCL19 expression in secondary lymphoid organs. plt mice have defects in the migration of naive T cells and activated dendritic cells into the T cell zones of lymphoid organs, suggesting that they would have defects in T cell immune responses. We now demonstrate T cell responses in plt mice are delayed but ultimately enhanced. Responses to contact sensitization are decreased at day 2 after priming but increased at day 6. After subcutaneous immunization, antigen-specific T cell proliferation and cytokine production in plt mice are increased and remain markedly elevated for at least 8 wk. Compared with wild-type mice, a proportion of T cell response in plt mice are shifted to the spleen, and prior splenectomy reduces the T cell response in draining lymph nodes. After immunization of plt mice, T cells and dendritic cells colocalize in the superficial cortex of lymph nodes and in splenic bridging channels, but not in T cell zones. These results demonstrate that plt mice mount robust T cell responses despite the failure of naive T cells and activated dendritic cells to enter the thymus dependent areas of secondary lymphoid organs.
Activation of Shaker Potassium Channels
Authors: Schoppa N.E. , Sigworth F.J.
Published: July 2002

The conformational changes associated with activation gating in Shaker potassium channels are functionally characterized in patch-clamp recordings made from Xenopus laevis oocytes expressing Shaker channels with fast inactivation removed. Estimates of the forward and backward rates for transitions are obtained by fitting exponentials to macroscopic ionic and gating current relaxations at voltage extremes, where we assume that transitions are unidirectional. The assignment of different rates is facilitated by using voltage protocols that incorporate prepulses to preload channels into different distributions of states, yielding test currents that reflect different subsets of transitions. These data yield direct estimates of the rate constants and partial charges associated with three forward and three backward transitions, as well as estimates of the partial charges associated with other transitions. The partial charges correspond to an average charge movement of 0.5 e0 during each transition in the activation process. This value implies that activation gating involves a large number of transitions to account for the total gating charge displacement of 13 e0. The characterization of the gating transitions here forms the basis for constraining a detailed gating model to be described in a subsequent paper of this series.
A Ca2+-induced Ca2+ Release Mechanism Involved in Asynchronous Exocytosis at Frog Motor Nerve Terminals
Authors: Narita K. , Akita T. , Osanai M. , Shirasaki T. , Kijima H. , Kuba K.
Published: July 2002

The extent to which Ca2+-induced Ca2+ release (CICR) affects transmitter release is unknown. Continuous nerve stimulation (20–50 Hz) caused slow transient increases in miniature end-plate potential (MEPP) frequency (MEPP-hump) and intracellular free Ca2+ ([Ca2+]i) in presynaptic terminals (Ca2+-hump) in frog skeletal muscles over a period of minutes in a low Ca2+, high Mg2+ solution. Mn2+ quenched Indo-1 and Fura-2 fluorescence, thus indicating that stimulation was accompanied by opening of voltage-dependent Ca2+ channels. MEPP-hump depended on extracellular Ca2+ (0.05–0.2 mM) and stimulation frequency. Both the Ca2+- and MEPP-humps were blocked by 8-(N,N-diethylamino)octyl3,4,5-trimethoxybenzoate hydrochloride (TMB-8), ryanodine, and thapsigargin, but enhanced by CN−. Thus, Ca2+-hump is generated by the activation of CICR via ryanodine receptors by Ca2+ entry, producing MEPP-hump. A short interruption of tetanus (<1 min) during MEPP-hump quickly reduced MEPP frequency to a level attained under the effect of TMB-8 or thapsigargin, while resuming tetanus swiftly raised MEPP frequency to the previous or higher level. Thus, the steady/equilibrium condition balancing CICR and Ca2+ clearance occurs in nerve terminals with slow changes toward a greater activation of CICR (priming) during the rising phase of MEPP-hump and toward a smaller activation during the decay phase. A short pause applied after the end of MEPP- or Ca2+-hump affected little MEPP frequency or [Ca2+]i, but caused a quick increase (faster than MEPP- or Ca2+-hump) after the pause, whose magnitude increased with an increase in pause duration (<1 min), suggesting that Ca2+ entry-dependent inactivation, but not depriming process, explains the decay of the humps. The depriming process was seen by giving a much longer pause (>1 min). Thus, ryanodine receptors in frog motor nerve terminals are endowed with Ca2+ entry-dependent slow priming and fast inactivation mechanisms, as well as Ca2+ entry-dependent activation, and involved in asynchronous exocytosis. Physiological significance of CICR in presynaptic terminals was discussed.
Every monotone graph property has a sharp threshold
Authors: Friedgut Ehud , Kalai Gil
Published: July 2002

In their seminal work which initiated random graph theory Erdös and Rényi discovered that many graph properties have sharp thresholds as the number of vertices tends to infinity. We prove a conjecture of Linial that every monotone graph property has a sharp threshold. This follows from the following theorem. Let

V
n

(
p
)
=
{
0
,
1

}
n

V_n(p)= \{0,1\}^n

denote the Hamming space endowed with the probability measure

μ
p

\mu _p

defined by
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="mu Subscript p Baseline left-parenthesis epsilon 1 comma epsilon 2 comma ellipsis comma epsilon Subscript n Baseline right-parenthesis equals p Superscript k Baseline dot left-parenthesis 1 minus p right-parenthesis Superscript n minus k">

μ
p

(

ϵ
1

,

ϵ
2

,
…
,

ϵ
n

)
=

p
k

⋅
(
1
−
p

)

n
−
k

\mu _p (\epsilon _1, \epsilon _2, \dots , \epsilon _n)= p^k \cdot (1-p)^{n-k}

, where

k
=

ϵ
1

+

ϵ
2

+
⋯
+

ϵ
n

k=\epsilon _1 +\epsilon _2 +\cdots +\epsilon _n

. Let

A
A

be a monotone subset of

V
n

V_n

. We say that

A
A

is symmetric if there is a transitive permutation group

Γ
\Gamma

on

{
1
,
2
,
…
,
n
}

\{1,2,\dots , n\}

such that

A
A

is invariant under

Γ
\Gamma

.

Theorem. For every symmetric monotone

A
A

, if

μ
p

(
A
)
>
ϵ

\mu _p(A)>\epsilon

then

μ
q

(
A
)
>
1
−
ϵ

\mu _q(A)>1-\epsilon

for

q
=
p
+

c
1

log
⁡
(
1

/

2
ϵ
)

/

log
⁡
n

q=p+ c_1 \log (1/2\epsilon )/\log n

. (

c
1

c_1

is an absolute constant.)
Composition operators on weighted Dirichlet spaces
Authors: Zorboska Nina
Published: July 2002

We characterize bounded and compact composition operators on weighted Dirichlet spaces. The method involves integral averages of the determining function for the operator, and the connection between composition operators on Dirichlet spaces and Toeplitz operators on Bergman spaces. We also present several examples and counter-examples that point out the borderlines of the result and its connections to other themes.
Composition operators on Hardy spaces of a half-plane
Authors: Matache Valentin
Published: July 2002

We consider composition operators on Hardy spaces of a half-plane. We mainly study boundedness and compactness. We prove that on these spaces there are no compact composition operators.
An algorithm for matrix extension and wavelet construction
Authors: Lawton W. , Lee S. , Shen Zuowei
Published: July 2002

This paper gives a practical method of extending an

n
×
r

n\times r

matrix

P
(
z
)

P(z)

,

r
≤
n

r \leq n

, with Laurent polynomial entries in one complex variable

z
z

, to a square matrix also with Laurent polynomial entries. If

P
(
z
)

P(z)

has orthonormal columns when

z
z

is restricted to the torus

T

\mathbf {T}

, it can be extended to a paraunitary matrix. If

P
(
z
)

P(z)

has rank

r
r

for each

z
∈

T

z\in \mathbf {T}

, it can be extended to a matrix with nonvanishing determinant on

T

\mathbf {T}

. The method is easily implemented in the computer. It is applied to the construction of compactly supported wavelets and prewavelets from multiresolutions generated by several univariate scaling functions with an arbitrary dilation parameter.
Percolation in the hyperbolic plane
Authors: Benjamini Itai , Schramm Oded
Published: July 2002

We study percolation in the hyperbolic planeH2\mathbb {H}^2and on regular tilings in the hyperbolic plane. The processes discussed include Bernoulli site and bond percolation on planar hyperbolic graphs, invariant dependent percolations on such graphs, and Poisson-Voronoi-Bernoulli percolation. We prove the existence of three distinct nonempty phases for the Bernoulli processes. In the first phase,p∈(0,pc]p\in (0,p_c], there are no unbounded clusters, but there is a unique infinite cluster for the dual process. In the second phase,p∈(pc,pu)p\in (p_c,p_u), there are infinitely many unbounded clusters for the process and for the dual process. In the third phase,p∈[pu,1)p\in [p_u,1), there is a unique unbounded cluster, and all the clusters of the dual process are bounded. We also study the dependence ofpcp_cin the Poisson-Voronoi-Bernoulli percolation process on the intensity of the underlying Poisson process.
An A₂ Bailey lemma and Rogers-Ramanujan-type identities
Authors: Andrews George , Schilling Anne , Warnaar S.
Published: July 2002

Using newqq-functions recently introduced by Hatayamaet al.and by (two of) the authors, we obtain an A2_2version of the classical Bailey lemma. We apply our result, which is distinct from the A2_2Bailey lemma of Milne and Lilly, to derive Rogers–Ramanujan-type identities for characters of the W3_3algebra.
Probing the Dynamics and Functions of Aurora B Kinase in Living Cells during Mitosis and Cytokinesis
Authors: Murata-Hori Maki , Tatsuka Masaaki , Wang Yu-Li
Published: July 2002

Aurora B is a protein kinase and a chromosomal passenger protein that undergoes dynamic redistribution during mitosis. We have probed the mechanism that regulates its localization with cells expressing green fluorescent protein (GFP)-tagged wild-type or mutant aurora B. Aurora B was found at centromeres at prophase and persisted until ∼0.5 min after anaphase onset, when it redistributed to the spindle midzone and became concentrated at the equator along midzone microtubules. Depolymerization of microtubules inhibited the dissociation of aurora B from centromeres at early anaphase and caused the dispersion of aurora B from the spindle midzone at late anaphase; however, centromeric association during prometaphase was unaffected. Inhibition of CDK1 deactivation similarly caused aurora B to remain associated with centromeres during anaphase. In contrast, inhibition of the kinase activity of aurora B appeared to have no effect on its interactions with centromeres or initial relocation onto midzone microtubules. Instead, kinase-inactive aurora B caused abnormal mitosis and deactivation of the spindle checkpoint. In addition, midzone microtubule bundles became destabilized and aurora B dispersed from the equator. Our results suggest that microtubules, CDK1, and the kinase activity each play a distinct role in the dynamics and functions of aurora B in dividing cells.
MULTICLUSTAL: a systematic method for surveying Clustal W alignment parameters.
Authors: Yuan J , Amend A , Borkowski J , DeMarco R , Bailey W , Liu Y , Xie G , Blevins R
Published: July 2002

MULTICLUSTAL is a Perl script designed to automate the process of alignment parameter choice for Clustal W with the goal of generating high quality multiple sequence alignments.
A genomic approach to understanding Heliothis and Helicoverpa resistance to chemical and biological insecticides
Authors: Heckel D. G. , Gahan L. J. , Daly J. C. , Trowell S.
Published: July 2002

Genomics is the comparative study of the structure and function of entire genomes. Although the complete sequencing of the genome of any insect pest is far in the future, a genomic approach can be useful in the study of mechanisms of insecticide resistance. We describe this strategy for
Heliothis
and
Helicoverpa
, two of the most destructive genera of pest moths (Lepidoptera) worldwide. Genome–wide linkage mapping provides the location of major and minor resistance genes. Positional cloning identifies novel resistance genes, even when the mechanisms are poorly understood, as with resistance to
Bacillus thuringiensis
toxins. Anchor loci provide the reference points for comparing the genomes and the genetic architecture of resistance mechanisms among related species. Collectively, these tools enable the description of the evolutionary response of related, but independent, genomes to the common selective pressure of insecticides in the environment. They also provide information that is useful for targeted management of specific resistance genes, and may even speed the search for families of novel insecticidal targets in Lepidoptera.
Elucidation of the genome organization of tobacco mosaic virus
Authors: Zaitlin Milton
Published: July 2002

Proteins unique to tobacco mosaic virus (TMV)–infected plants were detected in the 1970s by electrophoretic analyses of extracts of virus–infected tissues, comparing their proteins to those generated in extracts of uninfected tissues. The genome organization of TMV was deduced principally from studies involving
in vitro
translation of proteins from the genomic and subgenomic messenger RNAs. The ultimate analysis of the TMV genome came in 1982 when P. Goelet and colleagues sequenced the entire genome. Studies leading to the elucidation of the TMV genome organization are described.
Absorbed dose estimates to structures of the brain and head using a high‐resolution voxel‐based head phantom
Authors: Evans Jeffrey F. , Blue Thomas E. , Gupta Nilendu
Published: July 2002

The purpose of this article is to demonstrate the viability of using a high‐resolution 3‐D head phantom in Monte Carlo N‐Particle (MCNP) for boron neutron capture therapy (BNCT) structure dosimetry. This work describes a high‐resolution voxel‐based model of a human head and its use for calculating absorbed doses to the structures of the brain. The Zubal head phantom is a 3‐D model of a human head that can be displayed and manipulated on a computer. Several changes were made to the original head phantom which now contains over 29 critical structures of the brain and head. The modified phantom is a 85×109×120 lattice of voxels, where each voxel is 2.2×2.2×1.4 This model was translated into MCNP lattice format. As a proof of principle study, two MCNP absorbed dose calculations were made (left and right lateral irradiations) using a uniformly distributed neutron disk source with an energy spectrum. Additionally, the results of these two calculations were combined to estimate the absorbed doses from a bilateral irradiation. Radiobiologically equivalent (RBE) doses were calculated for all structures and were normalized to 12.8 Gy‐Eq. For a left lateral irradiation, the left motor cortex receives the limiting RBE dose. For a bilateral irradiation, the insula cortices receive the limiting dose. Among the nonencephalic structures, the parotid glands receive RBE doses that were within 15% of the limiting dose.
Thermoluminescent dosimetry of the Symmetra™ model I25.S06 interstitial brachytherapy seed
Authors: Patel Neil S. , Chiu‐Tsao Sou‐Tung , Williamson Jeffrey F. , Fan Pei , Duckworth Tamara , Shasha Daniel , Harrison Louis B.
Published: July 2002

As the efficacy of brachytherapy prostate treatment is becoming realized, new models of seeds are being introduced. In this article we present thermoluminescent dosimetry (TLD) in a solid water phantom for a new design of seed (UroMed/Bebig Symmetra™, Model I25.S06). TLD cubes, LiF TLD‐100, from Bicron (Solon, OH) with dimension were irradiated at various distances from the seed at angles ranging from 0° to 90° in 10° increments. The TLD detectors were calibrated by irradiation in a teletherapy beam. Monte Carlo simulation was used to account for TLD energy dependence and the deviation of solid water composition (as determined by chemical analysis of a sample) from liquid water. Dose rates per unit air kerma strength were determined based on calibrations traceable to the 1999 NIST standard (corrected for NIST measurement errors made in 1999) for the Symmetra™ seed. Dose data is presented in TG‐43 format as a function of distance and angle. Values for Λ, and the anisotropy constant are obtained for use in radiation treatment planning (RTP) software. The dose rate constant was determined to be which is comparable to model 6702 and higher than model 6711. We find the relative dose distributions of the Symmetra™ seed are similar to model 6702, and less anisotropic than model 6711. After accounting for deviation of measured solid water composition from the manufacturer's specification, good agreement between TLD results and Monte‐Carlo‐aided values was found.
Temperature dependence of polymer‐gel dosimeter nuclear magnetic resonance response
Authors: Spevacek Vaclav , Novotny Josef , Dvorak Pavel , Novotny Josef , Vymazal Josef , Cechak Thomas
Published: July 2002

The purpose of this study was to find a physical‐mathematical description capable to correct a polymer‐gel dosimeter relaxation rate ‐dose response for different temperatures. Four different modifications of polymer‐gel dosimeters were used in this study. Samples with polymer‐gel dosimeter in glass test vessels were homogeneously irradiated by gamma photons. A multi‐echo sequence with 16 equidistant echoes was used for evaluation of irradiated polymer‐gel dosimeters. The sequence parameters were as follows: TR 2000 ms, TE 22.5–360.0 ms, slice thickness 5 mm, FOV 255 mm, one acquisition. The proposed description recommends to subtract response of the nonirradiated dosimeter from the total ‐dose response. The relaxation rate for the irradiated dosimeter can be expressed as a function of temperature and dose. The temperature dependence has an exponential behavior in the measured range. The proposed description allows to correct the measured NMR ‐dose responses for different temperatures.
MR validation of soft tissue mimicing phantom deformation as modeled by nonlinear finite element analysis
Authors: Sciarretta Justin , Samani Abbas , Bishop Jonathan , Plewes Donald B.
Published: July 2002

A study of the applicability of nonlinear finite element analysis (FEA) to predict soft tissue deformation was validated with phase contrast magnetic resonance velocity imaging. A phantom of varying stiffness was placed in a special purpose, computer controlled MR compatible compression apparatus which provided precise, time varying compression with surface deformations on the order of 11%. The resulting motion was measured with MR velocity images acquired throughout the cycle of compression. The phantom geometry was modeled with a finite element mesh and the mechanical properties of the phantom material were measured and incorporated in the FEA model. The motion as calculated by the FEA model was compared to the motion measured with MRI and the results were found to vary with the material's Poisson's ratio and the coefficient of friction. A minimum difference was reached when the Poisson's ratio and coefficient of friction were set to 0.485 and 0.3, respectively. Under these conditions, the root mean square difference was found to be 14.4%.