bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical Training Increases eNOS Vascular Expression and Activity and Reduces Restenosis After Balloon Angioplasty or Arterial Stenting in Rats
Authors: Indolfi Ciro , Torella Daniele , Coppola Carmela , Curcio Antonio , Rodriguez Francisca , Bilancio Antonio , Leccia Antonio , Arcucci Oreste , Falco Mariacristina , Leosco Dario , Chiariello Massimo
Published: December 2002

The effects of dynamic exercise on restenosis after vascular injury are still unknown. The consequences of balloon dilation–induced injury on neointimal hyperplasia, vascular negative remodeling, and reendothelialization were assessed in sedentary and trained rats. Ex vivo eNOS vascular expression and activity were investigated in carotid arteries isolated from sedentary and exercised rats. The in vivo effects of eNOS inhibition by L-NMMA on vessel wall after balloon dilation were evaluated in sedentary and exercised rats. We also investigated the effects of exercise on neointimal formation in a rat stent model of vascular injury. Compared with sedentary group, the arteries isolated from trained rats showed higher levels of eNOS protein expression and activity 7 days after balloon dilation. A significant reduction of both neointimal hyperplasia and negative remodeling was observed 14 days after balloon injury in trained compared with sedentary rats. Moreover, we demonstrated that exercise training produced accelerated reendothelialization of the balloon injured arterial segments compared with sedentary. L-NMMA administration eliminated the benefits of physical training on vessel wall after balloon dilation. Finally, a decrease of neointimal hyperplasia as well as of platelet aggregation was observed after stent deployment in trained rats compared with sedentary. In conclusion, physical exercise could favorably affect restenosis after balloon angioplasty and stenting. Increase in eNOS expression and activity might contribute to the potential beneficial effects of exercise on the vessel wall after vascular injury.
Brain Natriuretic Peptide Is Produced in Cardiac Fibroblasts and Induces Matrix Metalloproteinases
Authors: Tsuruda Toshihiro , Boerrigter Guido , Huntley Brenda K. , Noser Josh A. , Cataliotti Alessandro , Costello-Boerrigter Lisa C. , Chen Horng H. , Burnett John C.
Published: December 2002

Cardiac fibroblasts (CFs) produce extracellular matrix proteins and participate in the remodeling of the heart. It is unknown if brain natriuretic peptide (BNP) is synthesized by CFs and if BNP participates in the regulation of extracellular matrix turnover. In this study, we examined the production of BNP in adult canine CFs and the role of BNP and its signaling system on collagen synthesis and on the activation of matrix metalloproteinases (MMPs). BNP mRNA was detected in CFs, and a specific radioimmunoassay demonstrated that BNP
1-32
was secreted into the media at a rate of 11.2±1.0 pg/10
5
cells per 48 hours (mean±SEM). The amount of BNP secretion was significantly (
P
<0.01) augmented by 10
−7
mol/L tumor necrosis factor-α in a time-dependent manner. BNP significantly (
P
<0.01) inhibited de novo collagen synthesis as assessed by [
3
H]proline incorporation, whereas zymographic MMP-2 (gelatinase) abundance was significantly (
P
<0.05) stimulated by BNP between 10
−7
and 10
−6
mol/L. In addition, protein expression of MMP-1, -2, and -3 and membranous type-1 MMP was significantly increased by 10
−6
mol/L BNP. The cGMP analogue 8-bromo-cGMP (10
−4
mol/L) mimicked the BNP effect, whereas inhibition of protein kinase G by KT5823 (10
−6
mol/L) significantly (
P
<0.05) attenuated BNP-induced zymographic MMP-2 abundance. In summary, this study reports that BNP is present in cultured CFs and that BNP decreases collagen synthesis and increases MMPs via cGMP–protein kinase G signaling. These in vitro findings support a role for BNP as a regulator of myocardial structure via control of cardiac fibroblast function.
Gene Expression in Fibroblasts and Fibrosis
Authors: Manabe Ichiro , Shindo Takayuki , Nagai Ryozo
Published: December 2002

Structural remodeling of the ventricular wall is a key determinant of clinical outcome in heart disease. Such remodeling involves the production and destruction of extracellular matrix proteins, cell proliferation and migration, and apoptotic and necrotic cell death. Cardiac fibroblasts are crucially involved in these processes, producing growth factors and cytokines that act as autocrine and paracrine factors, as well as extracellular matrix proteins and proteinases. Recent studies have shown that the interactions between cardiac fibroblasts and cardiomyocytes are essential for the progression of cardiac remodeling. This review addresses the functional role played by cardiac fibroblasts and the molecular mechanisms that govern their activity during cardiac hypertrophy and remodeling. A particular focus is the recent progress toward our understanding of the transcriptional regulatory mechanisms involved.
Tumor Necrosis Factor-α–Induced AT
1
Receptor Upregulation Enhances Angiotensin II–Mediated Cardiac Fibroblast Responses That Favor Fibrosis
Authors: Peng JianFeng , Gurantz Devorah , Tran Van , Cowling Randy T. , Greenberg Barry H.
Published: December 2002

Extracellular matrix (ECM) remodeling after myocardial infarction (MI) is an important determinant of cardiac function. Tumor necrosis factor-α (TNF-α) and angiotensin (Ang) II levels increase after MI and both factors affect fibroblast functions. The type 1 (AT
1
) receptor that mediates most Ang II effects is upregulated after MI in cardiac fibroblasts, and there is evidence that this is caused by TNF-α. We sought to determine if TNF-α–induced AT
1
receptor upregulation alters fibroblast responsiveness to Ang II and if this effect differs from direct TNF-α effects on fibroblast functions. In cultured neonatal rat cardiac fibroblasts, TNF-α reduced cellular [
3
H]-proline incorporation, increased matrix metalloproteinase-2 (MMP-2) activity and protein, and increased TIMP-1 protein levels. In cardiac fibroblasts with TNF-α–induced AT
1
receptor upregulation, Ang II–stimulated [
3
H]proline incorporation and TIMP-1 protein production was approximately 2-fold greater than in nonpretreated fibroblasts. Angiotensin II reduced MMP-2 activity and protein level only in TNF-α–pretreated fibroblasts. Angiotensin II effects were inhibited by selective AT
1
(but not AT
2
) receptor blockers. Thus, TNF-α–induced AT
1
receptor upregulation enhances Ang II–mediated functions that favor fibrosis. These effects are mostly directionally opposite of direct TNF-α effects on cardiac fibroblasts. Recognition of multifaceted TNF-α effects provides new insights into post-MI ECM remodeling.
Reduced Myocardial and Systemic
l
-Arginine Uptake in Heart Failure
Authors: Kaye David M. , Parnell Melinda M. , Ahlers Belinda A.
Published: December 2002

Altered nitric oxide (NO) bioavailability has been ascribed an important role in the pathophysiology of congestive heart failure (CHF). In the peripheral vasculature, we recently demonstrated a depression of
l
-arginine transport in association with pharmacological evidence of reduced endothelial function. In contrast, increased myocardial NO generation has been proposed to account for a component of the reduced myocardial contractility in CHF, although this remains controversial. We determined the whole body clearance rate and cardiac fractional extraction of
l
-arginine during a steady-state intravenous infusion of [
3
H]
l
-arginine (300 nCi/min) in 9 healthy control subjects and 7 patients with moderate to severe CHF. In patients with CHF, there was a 30% reduction in the transcardiac extraction of [
3
H]
l
-arginine compared with controls (
P
<0.05), which was accompanied by a trend toward reduced [
3
H]
l
-citrulline release (
P
=0.06). In conjunction, the systemic clearance rate of [
3
H]
l
-arginine was significantly lower in patients with CHF (778±148 versus 1278±144 mL/min,
P
<0.05). In association with these biochemical indices, we observed a 38% reduction (
P
<0.05) in the mRNA expression of the cationic amino acid transporter CAT-1 in ventricular myocardial samples from patients with CHF compared with healthy unused donor myocardium, whereas myocardial NOS enzymatic activity and NOS protein were unchanged. These data indicate the presence of a significant reduction in the myocardial uptake of
l
-arginine in patients with CHF. Furthermore, this abnormality seems to be part of a systemic downregulation of
l
-arginine transport.
Nicotinic Acid Adenine Dinucleotide Phosphate Mediates Ca
2+
Signals and Contraction in Arterial Smooth Muscle via a Two-Pool Mechanism
Authors: Boittin François-Xavier , Galione Antony , Evans A. Mark
Published: December 2002

Previous studies of arterial smooth muscle have shown that inositol 1,4,5-trisphosphate (IP
3
) and cyclic ADP-ribose mobilize Ca
2+
from the sarcoplasmic reticulum. In contrast, little is known about Ca
2+
mobilization by nicotinic acid adenine dinucleotide phosphate, a pyridine nucleotide derived from β-NADP
+
. We show here that intracellular dialysis of nicotinic acid adenine dinucleotide phosphate (NAADP) induces spatially restricted “bursts” of Ca
2+
release that initiate a global Ca
2+
wave and contraction in pulmonary artery smooth muscle cells. Depletion of sarcoplasmic reticulum Ca
2+
stores with thapsigargin and inhibition of ryanodine receptors with ryanodine, respectively, block the global Ca
2+
waves by NAADP. Under these conditions, however, localized Ca
2+
bursts are still observed. In contrast, xestospongin C, an IP
3
receptor antagonist, had no effect on Ca
2+
signals by NAADP. We propose that NAADP mobilizes Ca
2+
via a 2-pool mechanism, and that initial Ca
2+
bursts are amplified by subsequent sarcoplasmic reticulum Ca
2+
release via ryanodine receptors but not via IP
3
receptors.
Cell-Specific Regulatory Modules Control Expression of Genes in Vascular and Visceral Smooth Muscle Tissues
Authors: Hoggatt April M. , Simon Gina M. , Herring B. Paul
Published: December 2002

A novel approach with chimeric SM22α/telokin promoters was used to identify gene regulatory modules that are required for regulating the expression of genes in distinct smooth muscle tissues. Conventional deletion or mutation analysis of promoters does not readily distinguish regulatory elements that are required for basal gene expression from those required for expression in specific smooth muscle tissues. In the present study, the mouse telokin gene was isolated, and a 370-bp (−190 to 180) minimal promoter was identified that directs visceral smooth muscle–specific expression in vivo in transgenic mice. The visceral smooth muscle–specific expression of the telokin promoter transgene is in marked contrast to the reported arterial smooth muscle–specific expression of a 536-bp minimal SM22α (−475 to 61) promoter transgene. To begin to identify regulatory elements that are responsible for the distinct tissue-specific expression of these promoters, a chimeric promoter in which a 172-bp SM22α gene fragment (−288 to −116) was fused to the minimal telokin promoter was generated and characterized. The −288 to −116 SM22α gene fragment significantly increased telokin promoter activity in vascular smooth muscle cells in vitro and in vivo. Conversely, a fragment of the telokin promoter (−94 to −49) increased the activity of the SM22α promoter in visceral smooth muscle cells of the bladder. Together, these data demonstrate that both vascular- and visceral smooth muscle–specific regulatory modules direct gene expression in subsets of smooth muscle tissues.
A dominant negative form of the AAA ATPase SKD1/VPS4 impairs membrane trafficking out of endosomal/lysosomal compartments: class Evpsphenotype in mammalian cells
Authors: Fujita Hideaki , Yamanaka Motoko , Imamura Kanako , Tanaka Yoshitaka , Nara Atsuki , Yoshimori Tamotsu , Yokota Sadaki , Himeno Masaru
Published: December 2002

SKD1 is a member of the family of ATPases associated with cellular activities whose yeast homologue Vps4p has been implicated in endosomal/vacuolar membrane transports. When a mutant of SKD1 that lacks ATPase activity [SKD1(E235Q)] was overexpressed in mammalian cells, it induced a dominant negative phenotype characterized by aberrant endosomal structures (denoted as E235Q compartments). Expression of SKD1(E235Q) caused an accumulation of basolateral recycling receptors, such as asialoglycoprotein receptor and low-density lipoprotein in polarized hepatocytes and Madin-Darby canine kidney cells, respectively, in E235Q compartments. In addition, SKD1(E235Q) also abrogated, via endosomes, transport to the trans-Golgi network, as indicated by an accumulation of TGN38 in E235Q compartments. Three lines of evidence further demonstrated that SKD1 participates in the membrane transport from early endosomes to late endosomes/lysosomes: (1) a redistribution of a late endosomal and lysosomal membrane protein endolyn in E235Q compartments; (2) an inhibition of epidermal growth factor receptor degradation, due to an accumulation of the receptors in E235Q compartments; and (3) a mis-sorting of and defect in the proteolytic processing of newly synthesized cathepsin D. An intriguing finding was that the expression of SKD1(E235Q) caused the number of lysosomes to decrease (to one-sixth of control numbers) but their size to increase (2.4-fold larger in diameter than control lysosomes). Indeed, an ultrastructural analysis revealed that the expression of SKD1(E235Q) causes an accumulation of hybrid organelles formed by direct fusion between late endosomes and lysosomes. We conclude that SKD1 regulates multiple steps of membrane transport out of early endosomes and the reformation of lysosomes from a hybrid organelle.
COPII proteins are required for Golgi fusion but not for endoplasmic reticulum budding of the pre-chylomicron transport vesicle
Authors: Siddiqi Shadab A. , Gorelick Fred S. , Mahan James T. , Mansbach Charles M.
Published: December 2002

The budding of vesicles from endoplasmic reticulum (ER) that contains nascent proteins is regulated by COPII proteins. The mechanisms that regulate lipid-carrying pre-chylomicron transport vesicles (PCTVs) budding from the ER are unknown. To study the dependence of PCTV-ER budding on COPII proteins we examined protein and PCTV budding by using ER prepared from rat small intestinal mucosal cells prelabeled with 3H-oleate or 14C-oleate and 3H-leucine. Budded 3H-oleate-containing PCTVs were separated by sucrose density centrifugation and were revealed by electron microscopy as 142-500 nm vesicles. Our results showed the following: (1) Proteinase K treatment did not degrade the PCTV cargo protein, apolipoprotein B-48, unless Triton X-100 was added. (2) PCTV budding was dependent on cytosol and ATP. (3) The COPII proteins Sar1, Sec24 and Sec13/31 and the membrane proteins syntaxin 5 and rBet1 were associated with PCTVs. (4) Isolated PCTVs were able to fuse with intestinal Golgi. (5) Antibodies to Sar1 completely inhibited protein vesicle budding but increased the generation of PCTV; these changes were reversed by the addition of recombinant Sar1. (6) PCTVs formed in the absence of Sar1 did not contain the COPII proteins Sar1, Sec24 or Sec31 and did not fuse with the Golgi complex. Together, these findings suggest that COPII proteins may not be required for the exit of membrane-bound chylomicrons from the ER but that they or other proteins may be necessary for PCTV fusion with the Golgi.
Furrow microtubules and localized exocytosis in cleavingXenopus laevisembryos
Authors: Danilchik Michael V. , Bedrick Steven D. , Brown Elizabeth E. , Ray Kimberly
Published: December 2002

In dividing Xenopus eggs, furrowing is accompanied by expansion of a new domain of plasma membrane in the cleavage plane. The source of the new membrane is known to include a store of oogenetically produced exocytotic vesicles, but the site where their exocytosis occurs has not been described. Previous work revealed a V-shaped array of microtubule bundles at the base of advancing furrows. Cold shock or exposure to nocodazole halted expansion of the new membrane domain, which suggests that these microtubules are involved in the localized exocytosis. In the present report, scanning electron microscopy revealed collections of pits or craters, up to ∼1.5 μm in diameter. These pits are evidently fusion pores at sites of recent exocytosis, clustered in the immediate vicinity of the deepening furrow base and therefore near the furrow microtubules. Confocal microscopy near the furrow base of live embryos labeled with the membrane dye FM1-43 captured time-lapse sequences of individual exocytotic events in which irregular patches of ∼20 μm2 of unlabeled membrane abruptly displaced pre-existing FM1-43-labeled surface. In some cases, stable fusion pores, approximately 2 μm in diameter, were seen at the surface for up to several minutes before suddenly delivering patches of unlabeled membrane. To test whether the presence of furrow microtubule bundles near the surface plays a role in directing or concentrating this localized exocytosis, membrane expansion was examined in embryos exposed to D2O to induce formation of microtubule monasters randomly under the surface. D2O treatment resulted in a rapid, uniform expansion of the egg surface via random, ectopic exocytosis of vesicles. This D2O-induced membrane expansion was completely blocked with nocodazole, indicating that the ectopic exocytosis was microtubule-dependent. Results indicate that exocytotic vesicles are present throughout the egg subcortex, and that the presence of microtubules near the surface is sufficient to mobilize them for exocytosis at the end of the cell cycle.
External Ca2+ is predominantly used for cytoplasmic and nuclear Ca2+ increases in fertilized oocytes of the marine bivalveMactra chinensis
Authors: Deguchi Ryusaku , Morisawa Masaaki
Published: December 2002

Oocytes of the marine bivalve Mactra chinensis are spawned and arrested at the germinal vesicle stage (first meiotic prophase) until fertilization, without undergoing a process called oocyte maturation. As is the case of other animals, a fertilized oocyte of the bivalve displays increases in intracellular free Ca2+. We have clarified here the spatiotemporal patterns and sources of the intracellular Ca2+ changes at fertilization. Shortly after insemination, increased Ca2+ simultaneously appeared at the whole cortical region of the oocyte and spread inwardly to the center, attaining the maximal Ca2+ levels throughout the oocyte, including the cytoplasm and nucleus. The initial maximal Ca2+ peak was followed by a submaximal plateau phase of cytoplasmic and nuclear Ca2+ elevations, which persisted for several minutes. The nuclear envelope began to break down shortly before the termination of the plateau phase. These sperm-induced Ca2+ changes were inhibited by suppression of the influx of external Ca2+ from seawater but not by disturbance of the release of internal Ca2+ from inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]-sensitive stores, suggesting that the increased Ca2+ is from an external source. In contrast to the situation observed at fertilization, an oocyte artificially stimulated with serotonin (5-hydroxytryptamine, 5-HT) displayed repetitive Ca2+ transients, each of which started from one cortical region and propagated across the oocyte as a Ca2+ wave. The 5-HT-induced Ca2+ transients persisted even in the absence of external Ca2+. Experiments with caged Ins(1,4,5)P3 revealed that Ca2+ release from Ins(1,4,5)P3-sensitive stores is another pathway that is sufficient to trigger meiosis reinitiation from the first prophase. These results demonstrate that Mactra oocytes can potentially use two different Ca2+-mobilizing pathways: Ca2+ influx producing a centripetal Ca2+ wave from the whole cortex and Ca2+ release from Ins(1,4,5)P3-sensitive stores producing a point-source propagating Ca2+ wave. However, it seems likely that the Ca2+ influx pathway is predominantly activated at fertilization.
Polycomb group gene silencing proteins are concentrated in the perichromatin compartment of the mammalian nucleus
Authors: Cmarko Dusan , Verschure Pernette J. , Otte Arie P. , van Driel Roel , Fakan Stanislav
Published: December 2002

Human Polycomb group (PcG) proteins are involved in cell-type-dependent epigenetic gene silencing in an evolutionarily conserved manner. We have analysed the subnuclear localisation of these regulatory proteins in two different human cell lines and in rat liver tissue by means of light and electron immunomicroscopy using specific antibodies. We find that the PcG proteins HPC2, HPH1, BMI1 and RING1 are highly concentrated in the perichromatin compartment, situated at the surface of condensed chromatin domains. This compartment was demonstrated earlier to be the nuclear site where most pre-mRNA synthesis takes place. Interestingly, these PcG proteins are virtually absent from the interior of condensed chromatin areas. The present observations therefore show that transcriptionally active and PcG-silenced loci occur within the same spatially limited nuclear domain. Our novel high-resolution data strongly support the idea that epigenetic PcG-mediated gene silencing is a local event, rather than affecting large chromatin domains. In addition to being associated with the perichromatin region, PcG proteins also occur in the interchromatin space. Implications of these observations for higher order chromatin structure and for the mechanisms of PcG-mediated gene silencing are discussed.
Regulation of meiotic progression by the meiosis-specific checkpoint kinase Mek1 in fission yeast
Authors: Pérez-Hidalgo Livia , Moreno Sergio , San-Segundo Pedro A.
Published: December 2002

During the eukaryotic cell cycle, accurate transmission of genetic information to progeny is ensured by the operation of cell cycle checkpoints. Checkpoints are regulatory mechanisms that block cell cycle progression when key cellular processes are defective or chromosomes are damaged. During meiosis, genetic recombination between homologous chromosomes is essential for proper chromosome segregation at the first meiotic division. In response to incomplete recombination, the pachytene checkpoint (also known as the meiotic recombination checkpoint) arrests or delays meiotic cell cycle progression, thus preventing the formation of defective gametes. Here, we describe a role for a meiosis-specific kinase, Mek1, in the meiotic recombination checkpoint in fission yeast. Mek1 belongs to the Cds1/Rad53/Chk2 family of kinases containing forkhead-associated domains, which participate in a number of checkpoint responses from yeast to mammals. We show that defects in meiotic recombination generated by the lack of the fission yeast Meu13 protein lead to a delay in entry into meiosis I owing to inhibitory phosphorylation of the cyclin-dependent kinase Cdc2 on tyrosine 15. Mutation of mek1+ alleviates this chekpoint-induced delay, resulting in the formation of largely inviable meiotic products. Experiments involving ectopic overexpression of the mek1+ gene indicate that Mek1 inhibits the Cdc25 phosphatase, which is responsible for dephosphorylation of Cdc2 on tyrosine 15. Furthermore, the meiotic recombination checkpoint is impaired in a cdc25 phosphorylation site mutant. Thus, we provide the first evidence of a connection between an effector kinase of the meiotic recombination checkpoint and a crucial cell cycle regulator and present a model for the operation of this meiotic checkpoint in fission yeast.
Differential localization of WAVE isoforms in filopodia and lamellipodia of the neuronal growth cone
Authors: Nozumi Motohiro , Nakagawa Hiroyuki , Miki Hiroaki , Takenawa Tadaomi , Miyamoto Shigeaki
Published: December 2002

The formation and extension of filopodia in response to an extracellular stimulus by guidance cues determine the path of growth cone advance. Actin-filament bundling and actin polymerization at the tips supply the driving force behind the formation and elongation. We tried to clarify how signals in response to extracellular cues are transformed to induce filopodial generation and extension. Observations on the formation process of filopodia at growth cones in the neuroblastoma cell line NG108 showed that WAVE (WASP (Wiskott-Aldrich syndrome protein)-family verprolin homologous protein) isoforms played crucial and distinct roles in this process. WAVE1 was continuously distributed along the leading edge only and was not found in the filopodia. WAVE2 and WAVE3 discretely localized at the initiation sites of microspikes on the leading edge and also concentrated at the tips of protruding filopodia. We further found that WAVE isoforms localized at the filopodial tips through SHD (SCAR homology domain), next to its leucine zipper-like motif. Furthermore, time-lapse observations of filopodial formation in living cells showed that WAVE2 and WAVE3 were continuously expressed at the tips of filopodia during elongation. These results indicate that WAVE2 or WAVE3 may guide the actin bundles into the filopodia and promote actin assembly at the tips.
RNAi reveals anti-apoptotic and transcriptionally repressive activities of DAXX
Authors: Michaelson Jennifer S. , Leder Philip
Published: December 2002

The function of DAXX, a highly conserved mammalian gene, has remained controversial; this is due, in part, to its identification in a variety of yeast two-hybrid screens. Targeted deletion in the mouse revealed that DAXX is essential for embryonic development. Furthermore, the increased levels of apoptosis observed in Daxx-knockout embryos and embryonic stem cell lines suggested that DAXX functions in an anti-apoptotic capacity. In contrast, overexpression studies showed that DAXX may promote apoptosis. Additional studies showed that, when overexpressed, DAXX could function as a transcriptional repressor. To clarify these matters, we have used RNAi to deplete endogenous DAXX and thereby assess DAXX function in cell lines previously tested in overexpression studies. Increased apoptosis was observed in DAXX-depleted cells, showing DAXX to be anti-apoptotic. The apoptosis induced by the absence of DAXX was rescued by Bcl-2 overexpression. In addition, transcriptional derepression was observed in RNAi-treated cells, indicating the ability of endogenous DAXX to repress gene expression and allowing for the identification of novel targets of DAXX repression, including nuclear factor κB (NF-κB)- and E2F1- regulated targets. Thus, depletion of DAXX by RNAi has verified the crucial role of endogenous DAXX as an anti-apoptotic regulator, and has allowed the identification of probable physiological targets of DAXX transcriptional repression.
CaM kinase IIα mediates norepinephrine-induced translocation of cytosolic phospholipase A2 to the nuclear envelope
Authors: Fatima Soghra , Yaghini Fariborz A. , Ahmed Aftab , Khandekar Zinat , Malik Kafait U.
Published: December 2002

Several growth factors, hormones and neurotransmitters, including norepinephrine, increase cellular calcium levels, promoting the translocation of cytosolic phospholipase A2 to the nuclear envelope. This study was conducted to investigate the contributions of the calcium-binding protein calmodulin and of calcium—calmodulin-dependent protein kinase II to cytosolic phospholipase A2 translocation to the nuclear envelope elicited by norepinephrine in rabbit aortic smooth-muscle cells. Norepinephrine caused cytosolic phospholipase A2 accumulation around the nuclear envelope as determined from its immunofluorescence; cytosolic phospholipase A2 translocation was blocked by inhibitors of calmodulin and calcium—calmodulin-dependent protein kinase II or calcium—calmodulin-dependent protein kinase IIα antisense oligonucleotide. Calmodulin and calcium—calmodulin-dependent protein kinase II inhibitors did not prevent cytosolic calcium increase but attenuated cytosolic phospholipase A2 phosphorylation caused by norepinephrine or ionomycin. In vascular smooth-muscle cells reversibly permeabilized with β-escin and treated with alkaline phosphatase, norepinephrine failed to cause cytosolic phospholipase A2 phosphorylation and translocation to the nuclear envelope; these effects of norepinephrine were minimized by the phosphatase inhibitor okadaic acid. Recombinant cytosolic phospholipase A2 phosphorylated by purified calcium—calmodulin-dependent protein kinase II, but not unphosphorylated or dephosphorylated cytosolic phospholipase A2, introduced into permeabilized vascular smooth-muscle cells in the absence of calcium accumulated around the nuclear envelope. These data suggest that norepinephrine-induced translocation of cytosolic phospholipase A2 to the nuclear envelope is mediated by its phosphorylation by calcium—calmodulin-dependent protein kinase II and that calcium alone is insufficient for cytosolic phospholipase A2 translocation to the nuclear envelope in rabbit vascular smooth-muscle cells.
4,7,11,14,18,21-Hexa-t-butyltribenzodecacyclenyl Radical: A Six-Stage Amphoteric Redox System
Authors: Kubo Takashi , Yamamoto Kagetoshi , Nakasuji Kazuhiro , Takui Takeji , Murata Ichiro
Published: December 2002

A six-stage amphoteric redox hydrocarbon radical 3• containing three phenalenyl units was prepared. Cyclic voltammogram of 3• exhibits six reversible redox waves with a small numerical sum (E1sum) of first oxidation (E1ox) and reduction (E1red) potentials. Some redox states of 3• were successfully generated from the neutral 3• and characterized by NMR, ESR, UV-vis-NIR spectroscopies, and theoretical calculations. The spin and the charges are delocalized over the entire C3 molecule of 33+, 3•2+, 3•, and 33−. On the other hand, 3•2− shows the localization of the spin on one phenalenyl unit; these results are consistent with the distorted C2 structure caused by the Jahn-Teller effect.
Crystal and Molecular Structures of 2-Dodecyl-7,7,8,8-tetracyanoquinodimethane
Authors: Terashita Shin-ichi , Suzuki Takashi , Nakatsu Kazumi , Iriyama Keiji , Ozaki Yukihiro
Published: December 2002

To develop a possible structural model for molecular arrangement in Langmuir–Blodgett (LB) films of 2-alkyl-7,7,8,8-tetracyanoquinodimethane (alkyl-TCNQ) the molecular and crystal structures of 2-dodecyl-7,7,8,8-tetracyanoquinodimethane (dodecyl-TCNQ) have been determined by X-ray single-crystal analysis. The compound crystallizes in the triclinic space group P1- with Z = 2. The molecule consists of the planar TCNQ moiety and the dodecyl chain having all-trans conformation. In the crystals the TCNQ fragments make a stacking structure in a head-to-head manner across the centers of symmetry to form a double layer of TCNQ groups. The dodecyl chains protrude oppositely from the TCNQ layers and are assembled to form a close-packed layer, being interdigitated with each other. In this way, the TCNQ moieties and the dodecyl groups form layers alternately. This molecular arrangement in the crystal provides new insight into the structure of the LB films of alkyl-TCNQ.
Voltammetric Behavior of Menadione in Surfactant Media and Its Determination in Sodium Dodecyl Sulfate Surfactant System
Authors: Jaiswal Priya V , Ijeri Vijaykumar S , Srivastava Ashwini K
Published: December 2002

Cyclic voltammograms at the carbon paste electrode were recorded for menadione or vitamin K3 dissolved in aqueous surfactant solutions above their critical micellization concentrations. The reduction and oxidation potentials of the vitamin were found to be different in different surfactants and were found also to vary with change in the surfactant concentration. Differential pulse voltammetric technique was utilized for the determination of the vitamin in the above surfactant systems. The limit of detection and the linear range varied in different surfactants, the lowest being in the sodium dodecyl sulfate surfactant systems. Similarly, cyclic voltammograms were recorded for ascorbic acid and the effect of various surfactants on its oxidation peak was also studied. Simultaneous determination of menadione, ascorbic acid, and riboflavin was attempted. Synthetically prepared samples were analyzed and gave satisfactory results.
Sol–Gel Prepared Sn–Al2O3 Catalysts for the Selective Reduction of NO with Propene
Authors: Haneda Masaaki , Ohzu Shin-ichi , Kintaichi Yoshiaki , Shimizu Ken-ichi , Shibata Junji , Yoshida Hisao , Hamada Hideaki
Published: December 2002

Catalytic reduction of NO by propene in the presence of oxygen was studied over Sn–Al2O3 prepared by the sol–gel method. The maximum NO conversion did not change much with Sn loading (1–5 wt%), although the effective temperature window for NO reduction shifted to lower temperatures with increasing Sn loading. X-ray diffraction (XRD), and X-ray absorption spectroscopy (XANES and EXAFS) revealed the formation of finely-divided SnO2 crystallites in Sn–Al2O3. It was deduced that not only the surface vicinity of supported SnO2, which can be reduced at lower temperatures, but also alumina participate in the reaction as catalytically active sites. The catalytic performance of Sn–Al2O3 was markedly improved by an H2O treatment at 873 K. The H2O treatment did not affect the crystal structure of the catalysts and the dispersion state of supported SnO2, but promoted the removal of Cl− ions, which originated from the SnCl4 precursor. The activity enhancement by the H2O treatment was accounted for by an increase in the surface SnO2 concentration as active sites and by the modification of oxo-tin species as active sites. Reaction kinetic studies suggested that NO reduction on the fresh and the H2O-treated catalysts proceeds through the same reaction pathway in which the surface NOx adspecies and C3H6-derived species play an important role for NO reduction.
Binding of Phenol Derivatives to Nonionic Surfactant Micelles as Studied by Capillary Zone Electrophoresis
Authors: Takayanagi Toshio , Motomizu Shoji
Published: December 2002

Binding constants of 13 kinds of phenols as neutral and anionic species to nonionic surfactant micelles were determined using their mobility changes in capillary zone electrophoresis. Electrophoretic mobility of the phenolate ions at alkaline regions decreased with increasing the concentrations of nonionic surfactant. Analyzing such mobility decreases provided the binding constants of the ions (KB,A). The KB,A values are larger in the anions which are more hydrophobic. Binding constants of the phenols as their neutral species to nonionic surfactant micelles (KB,HA) were also determined by using the difference in acid dissociation constants between in the absence of and in the presence of nonionic surfactant micelles: in the presence of the surfactant, the apparent pKa values became larger, which indicates that the neutral species are more likely bound to the micelles. The KB,A and KB,HA values determined were compared with each other on the basis of hydrophobicity, basicity, and position of the substituents.
Comparative Structural, Spectroscopic and Redox Studies of Isostructural Complexes of Ruthenium(III), Osmium(III), and Rhenium(III): cis-Dichloro Complexes Containing Tris(2-pyridylmethyl)amine and Its 6-Methylpyridyl Derivative
Authors: Sugimoto Hideki , Matsunami Chikako , Koshi Chikako , Yamasaki Mikio , Umakoshi Keisuke , Sasaki Yoichi
Published: December 2002

A series of the complexes, [MCl2(L)]+ (M = Ru, L = tpa (1), Metpa (1a); M = Os, L = tpa (2); M = Re, L = tpa (3), Metpa (3a); tpa = tris(2-pyridylmethyl)amine, Metpa = ((6-methyl-2-pyridylmethyl)bis(2-pyridylmethyl)amine), have been prepared. X-ray structural analyses of the series of isostructural complexes [1a]BF4, [2]PF6·C2H5OC2H5, [3]BF4, and [3a]BF4 together with that of the previously reported [1]ClO4, made detailed comparison of structure parameters for Ru, Os, and Re possible. The corresponding metal-ligand bond lengths which are similar between [1]ClO4 and [2]PF6·C2H5OC2H5 are considerably longer (0.02–0.03 Å) for [3]BF4, especially in the case of M–N(tertially nitrogen) (0.06 Å) bond. The M–Cl(trans to tertially nitrogen) bond lengths do not follow this trend. Introduction of the methyl group causes significant influence on the structure of the Re(III) complex: increase in bond length of Re–N(methylated pyridyl) and Re–N(pyridyl) trans to it. Bond angles around the metal ion related to the methylated pyridyl group are also significantly affected. Such steric influence is not clear for [1a]BF4 due to disorder of methyl group. The redox waves of the two processes, M(II/III) and M(III/IV), are observed for all the complexes. The redox potentials for individual process follow the order: Ru < Os < Re (from negative to positive), the difference being ca. 0.5 V. The difference in the two consecutive redox potentials is almost identical (ca. 1.6 V) among the three metal ions, suggesting that the stabilities of the trivalent oxidation state over di- and tetravalent ones are not affected by the different d-electron configurations. Strong visible MLCT bands are observed only for the rhenium(III) complexes. This may be due to higher d-orbital energies of the rhenium(III) ion as evidenced from the redox potentials.
Synthesis, Structures and Characterization of the Dinuclear Nickel(II) Complexes Containing N,N,N′,N′-Tetrakis[(1-ethyl-2-benzimidzolyl)- methyl]-2-hydroxy-1,3-diaminopropane and their Urea Complexes Relevant to the Urease Active Site
Authors: Yamane Heitaro , Nakao Yasuo , Kawabe Satoru , Xie Yong , Kanehisa Nobuko , Kai Yasushi , Kinoshita Masashi , Mori Wasuke , Hayashi Yasuhisa
Published: December 2002

New dinuclear nickel(II) complexes ([Ni2(L-Et)(CH2ClCOO)(H2O)2](ClO4)2·H2O (3), [Ni2(L-Et)(CCl3COO)(H2O)2](ClO4)2·H2O (4), [Ni2(L-Et)(CF3COO)(H2O)2](ClO4)2·3H2O (5)) and their urea complexes ([Ni2(L-Et)(RCOO)(ur)(H2O)](ClO4)2 (R = CH3 (6), C2H5 (7), CH2Cl (8), CCl3 (9), CF3 (10)) (HL-Et = N,N,N′,N′-tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane and ur = urea) have been prepared in order to model the active site urease. These complexes were characterized by IR and UV-vis spectra, and by magnetic susceptibilities. The crystal structures of the complexes [Ni2(L-Et)(CH2ClCOO)(CH3OH)2](ClO4)2 (3′) and [Ni2(L-Et)(OAc)(ur)(H2O)](ClO4)2· 2(CH3)2CO (OAc = acetate) (6′) were determined by X-ray crystallography. In the cation of 6′, the two nickel(II) ions are bridged by an alkoxo of L-Et− and an acetato, and a monodentate urea molecule is attached to a nickel(II) through its oxygen atom. Variable temperature magnetic susceptibility measurements of the urea complexes 6, 8, and 10 show an antiferromagnetic exchange coupling (2J = −15.8, −8.0, and −13.3 cm−1 for 6, 8, and 10, respectively, Hamiltonian H = −2JS1·S2 with S1 = S2 = 1) between two nickel(II) ions.
Structure and Magnetic Property of Ru(II,III) Dimer Axially Coordinated by the Niroxide Radical and Water [Ru2(O2CCMe3)4(nitph)(H2O)]BF4, nitph = 2-Phenyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-N-oxide
Authors: Sayama Yasuyoshi , Handa Makoto , Mikuriya Masahiro , Hiromitsu Ichiro , Kasuga Kuninobu
Published: December 2002

A ruthenium(II,III) pivalate dimer axially coordinated by a nitroxide radical and a water molecule, [Ru2(O2CC-Me3)4(nitph)(H2O)]BF4 (nitph = 2-phenyl-4,4,5, 5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-N-oxide), has been prepared and characterized. The magnetic interaction between the Ru(II,III) core and the radical through the coordinated N–O group was estimated to be J = −45 cm−1.
Effect of Palladium Dispersion on the Enantioselective Hydrogenation of α,β-Unsaturated Acids with Modified Pd/TiO2 Catalysts
Authors: Nitta Yuriko , Kubota Takeshi , Okamoto Yasuaki
Published: December 2002

The enantioselective hydrogenation of the C=C double bonds in (E)-2-methyl-2-butenoic acid, (E)-2-methyl-2-pentenoic acid, and (E)-2,3-diphenyl-2-propenoic acid has been studied using cinchonidine-modified Pd/TiO2 catalysts with different metal loadings of between 0.5 to 30 wt%. For all of the substrates examined, those catalysts with degrees of Pd dispersion lower than 0.2 have been shown to be rather detrimental for obtaining a high enantioselectivity, as opposed to the tendencies reported for the hydrogenations of keto esters with modified Pt and Ni systems. The hydrogenations of the aliphatic acids are almost structure insensitive with a slight decrease in the enantioselectivity at Pd dispersions lower than 0.2, which is in great contrast to the hydrogenation of the aromatic acid. A similar difference in the structure sensitivity has been observed with catalysts modified by a larger modifier, (−)-dihydroapovincaminic acid ethyl ester. The influence of the substrate structure on the adsorption mode and the strength of the modifier-substrate complex is discussed in relation to the size of the Pd ensemble on the catalyst surface.
Conformational Mobility of the Bridged Calix[6]arenes with Allyl and Ethyl Groups at the Lower Rim
Authors: Akine Shigehisa , Goto Kei , Kawashima Takayuki
Published: December 2002

The conformational mobility of the bridged calix[6]arenes with allyl and ethyl groups at the lower rim was investigated. Allylation of the tetrahydroxy compounds afforded two isomers: 5a (cone) and 5b (1,2,3-alternate), which were separated by silica-gel chromatography. These isomers underwent slow isomerization at room temperature with a half-life time of about 2 weeks. On the other hand, the ethyl derivatives 6–9 were found to exist as mixtures of conformational isomers in solution; they were observed independently on the NMR time-scale but were inseparable on the laboratory time-scale. The ratios of two isomers of 6–9 depended on the functionality on the bridging unit, the effects of which were investigated by molecular mechanics calculations. In the crystalline state, the ethyl derivative 6 with a bromo functionality was found to take the 1,2,3-alternate conformation, while compound 7 with an ethynyl group adopted the cone conformation.
Efficient Dimerization of Formic Acid in Aqueous Solution Induced by Ar-Arc Plasma
Authors: Harada Kaoru , Ito Yoshimi , Wada Toshinori , Munegumi Toratane
Published: December 2002

Introduction of argon-arc plasma into an aqueous solution of formic acid resulted in the formation of oxalic acid. The reaction conditions for the dimerization were studied. The maximum yield of oxalic acid reached 47–50% when the reaction was carried out using sodium formate or calcium formate. Dimerization of acetic acid was also examined.
Observation of the Pathway from Lysine to the Isoprenoidal Lipid of Halophilic Archaea, Halobacterium halobium and Natrinema pallidum, Using Regiospecifically Deuterated Lysine
Authors: Yamauchi Noriaki , Endoh Satoshi , Kato Keiko , Murae Tatsushi
Published: December 2002

We examined the incorporation of lysine into archaeal isoprenoidal lipids of halophilic archaea, Natrinema pallidum and Halobacterium halobium using two regiospecifically deuterium-labeled derivatives, [3,3-2H2] and [6,6-2H2]lysines. The two deuterated lysines were synthesized, and the incorporation of deuterium to the lipid core was defined by 2H NMR. The results revealed that lysine is degraded to crotonoyl-CoA by the decarboxylation of carboxylate in the metabolism of halophilic archaea, much like the metabolism of lysine in aerobic bacteria; the process converts lysine to isoprenoidal lipids via the mevalonate pathway through glutaryl-CoA, crotonoyl-CoA, and acetoacetyl-CoA.
Molecular Dynamics Simulation of Neocarrabiose 2,4′-Bis(sulfate) and Carrabiose 4′,2-Bis(sulfate) as Building Blocks of ι-Carrageenan in Water
Authors: Ueda Kazuyoshi , Iwama Koji , Nakayama Haruo
Published: December 2002

Molecular mechanics and molecular dynamics simulations were performed on two types of disaccharides, neocarrabiose 2,4′-bis(sulfate) and carrabiose 4′,2-bis(sulfate), which are building blocks of ι-carrageenan. Although the conformation and potential-energy surfaces of these disaccharides have been investigated by several researchers, all of them were analyzed using a vacuum calculation. To investigate the conformational behavior of these molecules in water, we performed a molecular dynamics simulation with the presence of explicit water molecules and counter ions around the disaccharides. The trajectories of the glycosidic dihedral angles in the water simulation reproduced the potential-energy surface calculated not with a dielectric constant of 80, but with 1. The electrostatic force was found to act so as to restrict the allowed area of the potential-energy surfaces. The most stable conformation of neocarrabiose 2,4′-bis(sulfate) is φ = 162, ψ = 174. Although the global minimum conformation of carrabiose 4′,2-bis(sulfate) is at A1 (φ = 176° and ψ = −166°), the molecular dynamics simulation in water suggested that the structure, B1 (φ = 164° and ψ = −87°), is more stable than A1 by analyzing the trajectory and the hydrogen bonds with water molecules. This indicates that it is important for the conformational analysis to take into account the solvation effect explicitly. The structure of B1 agrees with that found by an NMR experiment.
Thermochromism and Solvatochromism by Reversible Dye Aggregation in Sugar-Gel Matrices
Authors: Matsushima Ryoka , Okuda Hideki , Aida Madoka , Ogiue Atsushi
Published: December 2002

Upon changes in temperature or solvent, extensive and reversible color changes (e.g., blue to pink) were observed with a cationic flavylium dye in sugar-gel matrices, such as agar, agarose, pectin, sodium alginate, and carrageenan gels, whereas only small spectral changes were found in methylcellulose gel or in the absence of any sugar gels. During many repeated cycles of warming and cooling no indications of significant fatigue were observed, demonstrating a high thermochromic reversibility. Comparable thermochromism and solvatochromism were observed with the well-known cationic dye Methylene Blue in the sugar-gel matrices. In the presence of an anionic surfactant in place of sugar gel, extensive color changes were also observed while no changes were observed at all in the presence of a cationic surfactant, thus implying an important role of the electrostatic interactions between the cationic dye and anionic surfaces or species. It has been assumed that the cationic dyes are reversibly coagulated or condensed on the negatively charged colloid-gel surface to enhance dye aggregation.
Enthalpy–Entropy Compensation of Cyclodextrin Complexation with Different Classes of Substrates
Authors: Liu Lei , Yang Chao , Guo Qing-Xiang
Published: December 2002

In this study, it was found that in the molecular recognition of cyclodextrins, the guest compounds fall clearly into different classes according to the behavior of enthalpy–entropy compensation. Good enthalpy–entropy compensation takes place when the substrates are hydrophobic, whereas poor or no enthalpy–entropy compensation occurs when the substrates are relatively hydrophilic. A thermodynamic theory is proposed to explain the behaviors, and it is suggested that solvent molecular reorganization constitutes the physical origin of the enthalpy–entropy compensation in cyclodextrin complexation.