bluuebunny/crossref_metadata_2025 huggingface dataset:
N-Cadherin Upregulation and Function in Response of Smooth Muscle Cells to Arterial Injury
Authors: Jones Mara , Sabatini Peter J.B. , Lee Frank S.H. , Bendeck Michelle P. , Langille B. Lowell
Published: December 2002

Objective—

Smooth muscle cell migration is critical to neointimal formation after arterial injury. The purpose of this study was to elucidate the regulation and functional significance of cell-cell adhesion via adherens junctions during this process.

Methods and Results—

Using balloon catheter injury of rat carotid artery, we showed that neointimal formation is accompanied by dramatic but transient upregulation of intimal N-cadherin and associated catenins, proteins that mediate adhesion at adherens junctions. Upregulation was demonstrated by immunofluorescence microscopy and by immunoblotting, and it coincided with evidence of phenotypic modulation of smooth muscle cells. Similar upregulation was observed when postconfluent cultures of porcine aortic smooth muscle cells were subjected to linear denuding injuries. Furthermore, treatment of wounded cultures with a blocking antibody against the extracellular domain of the N-cadherin protein significantly suppressed the repair of wounds.

Conclusions—

N-cadherin and associated proteins are dynamically regulated during neointimal formation and provide evidence that this regulation is important for migratory repair. Therefore, N-cadherin may provide a novel target for therapies that are directed toward intimal proliferative disorders, including restenosis and vascular bypass graft failure.
Apolipoprotein E and Lipoprotein Lipase Increase Triglyceride-Rich Particle Binding but Decrease Particle Penetration in Arterial Wall
Authors: Mullick Adam E. , Deckelbaum Richard J. , Goldberg Ira J. , Al-Haideri Maysoon , Rutledge John C.
Published: December 2002

Objective—

Liver-derived apolipoprotein E (apoE) decreases atherosclerosis without altering the circulating concentrations of plasma lipoproteins. We evaluated the effects of apoE and lipoprotein lipase (LpL) on the interactions of triglyceride-rich particles (TGRPs) in the arterial wall.

Methods and Results—

Quantitative fluorescence microscopy was used to study the interactions of TGRPs (25- to 35-nm diameter) in the arterial wall. Carotid arteries were harvested from rats, placed in a perfusion chamber, and perfused with fluorescently labeled TGRPs. In the absence of apoE or LpL, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine-TGRP (100 μg neutral lipid/mL) was poorly retained in the arterial wall. The addition of either apoE (10 μg/mL) or LpL (10 μg/mL) increased TGRP accumulation 220% and 100%, respectively. This effect was attenuated by heparin (10.0 IU/mL). Histological analyses of cross sections from these vessels demonstrate that in the absence of apoE or LpL, there is deep penetration of lipid into the arterial wall. With the addition of either apoE or LpL, arterial wall penetration of TGRP is blocked.

Conclusions—

These results demonstrate that although apoE and LpL increase arterial wall accumulation of TGRPs, these proteins also reduce the penetration of TGRPs into the arterial wall. We postulate that this may represent a novel antiatherogenic property of apoE and LpL.
Nonnuclear Actions of Estrogen
Authors: Ho Karen J. , Liao James K.
Published: December 2002

Estrogen has long been observed to endow cardiovascular protective effects, as evidenced by sex-specific differences in the incidence of hypertensive and coronary artery disease, the development of atherosclerosis, and myocardial remodeling after infarction. To exert its tissue-specific effects, the classic estrogen receptor (ER) functions as a ligand-dependent transcription factor. However, there is growing evidence that in response to 17β-estradiol and heterologous signals, the ER can also mediate signaling cascades at the membrane and in the cytoplasm via various second messengers, such as receptor-mediated protein kinases. This review summarizes the current understanding of nonnuclear ER signaling and discusses the relevance to eliciting the beneficial cardiovascular effects of estrogen. These include vasodilation, inhibition of response to vessel injury, limiting myocardial injury after infarction, and attenuating cardiac hypertrophy. Defining the full repertoire of ER function promises to expose novel, highly specific targets for pharmacological interventions and may ultimately lead to the primary and secondary prevention of cardiovascular diseases.
Mast Cell Tryptase Degrades HDL and Blocks Its Function as an Acceptor of Cellular Cholesterol
Authors: Lee Miriam , Sommerhoff Christian P. , von Eckardstein Arnold , Zettl Frank , Fritz Hans , Kovanen Petri T.
Published: December 2002

Objective—In human atherosclerotic lesions, degranulated mast cells are found in the vicinity of macrophage foam cells. Mast cell granules contain tryptase, a tetrameric serine protease requiring glycosaminoglycans for stabilization. No endogenous inhibitors have been described for tryptase, and the physiological functions of the enzyme are poorly understood. Here, we investigated the effects of human tryptase on the integrity of high density lipoprotein (HDL)3and on its ability to release cholesterol from cultured mouse macrophage foam cells.

Methods and Results—Incubation of HDL3with tryptase led to degradation of its apolipoproteins. Tryptase predominantly degraded a quantitatively minor subfraction of HDL3that is lipid poor, exhibits electrophoretic pre-β mobility, and contains either apolipoprotein A-I or apolipoprotein A-IV as its sole apolipoprotein. Moreover, tryptase caused functional changes in HDL3by destroying its ability to promote high-affinity efflux of cholesterol from macrophage foam cells, ie, the pre-β-HDL-dependent component of the process. Human aortic proteoglycans increased the ability of tryptase to proteolyze HDL3, suggesting that the proteoglycan-rich extracellular matrix of the arterial intima provides an appropriate environment for the extracellular actions of tryptase.

Conclusions—By depleting pre-β-HDL, mast cell tryptase may impair the initial step of reverse cholesterol transport and will then favor cellular accumulation of cholesterol during atherogenesis.
Differential Gene Expression in Vascular Smooth Muscle Cells in Primary Atherosclerosis and In Stent Stenosis in Humans
Authors: Zhang Qi Jun , Goddard Martin , Shanahan Catherine , Shapiro Leonard , Bennett Martin
Published: December 2002

Objective—

We sought to identify differentially expressed genes in human in stent stenosis (ISS) to provide insights into the mechanism of disease.

Methods and Results—

Using representation difference analysis, we examined differential gene expression between cultured normal human medial vascular smooth muscle cells (VSMCs) and cells from primary atherosclerotic plaques or ISS sites. Specific groups of genes were overexpressed in ISS and plaque VSMCs, including cell cycle regulatory proteins and cell matrix and contractile proteins. Differential expression was validated by virtual Northern analysis, reverse transcriptase-polymerase chain reaction, in situ hybridization, and immunohistochemistry. All ISS genes were expressed by normal intima and had even higher expression in primary plaque VSMCs.

Conclusions—

ISS VSMCs have a stable gene expression profile reflecting an intimal pattern, intermediate between normal medial and primary plaque VSMCs. Differential expression profiling may identify markers of disease that are overexpressed in ISS and also help elucidate the origin of the ISS lesion.
Increased Platelet-Collagen Interaction Associated With Double Homozygosity for Receptor Polymorphisms of Platelet GPIa and GPIIIa
Authors: Pontiggia Luca , Lassila Riitta , Pederiva Stephanie , Schmid Hans-Rudolf , Burger Mirjam , Beer Juerg H.
Published: December 2002

Objective—

There is considerable controversy regarding the clinical role of the single-nucleotide polymorphisms (SNPs) of the platelet glycoprotein receptor GPIa C807T and the Pl
A1/A2
of GPIIIa as cardiovascular risk factors. We hypothesized that two combined SNPs in their homozygous prothrombotic forms could clarify their pathophysiological impact.

Methods and Results—

We identified a family with a striking history of premature cardiovascular events and a high frequency of the prothrombotic form of the two SNPs. From this family, the platelets of a healthy, 27-year-old propositus with this double homozygosity were compared with three matched male neutral gene variant controls. The propositus had shortened PFA-100 closure times and an increased platelet aggregation response to collagen. Platelet deposition to collagen was augmented under the blood flow conditions of a high shear rate model (1600 s
−1
). Platelet adhesion on collagen monomers was induced in a static system, leading to the promotion of subsequent procoagulant activity.

Conclusions—

The combined homozygous prothrombotic SNPs of GPIa and GPIIIa are associated with an increased platelet–collagen interaction and procoagulant activity that can be readily demonstrated in several independent systems. Our patient may serve as a useful model for the functional consequences of two combined, potentially procoagulant, platelet SNPs.
Characterization of the Association of Tissue Factor Pathway Inhibitor With Human Placenta
Authors: Mast Alan E. , Acharya Nayana , Malecha Mark J. , Hall Connie L. , Dietzen Dennis J.
Published: December 2002

Objective—

Tissue factor pathway inhibitor (TFPI) is an endothelial-associated inhibitor of blood coagulation. Because the mechanism for attachment of TFPI to endothelium is not clear, we investigated its association with human placenta.

Methods and Results—

Western blots demonstrate that treatment with phosphatidylinositol-specific phospholipase C (PIPLC) removes more placental TFPI than either PBS or heparin, a finding confirmed by immunohistochemistry. The amounts of heparin-releasable and PIPLC-releasable TFPI activity on placental endothelium were measured in placentas from 5 individuals. PIPLC removes >10-fold more TFPI activity from the placental fragments than 10 U/mL heparin and >100-fold more than 1 U/mL heparin. Pretreatment of the placental fragments with PIPLC increases the amount of heparin-releasable TFPI by ≈3-fold. An antibody specific for the C-terminal region of TFPI recognizes PIPLC-releasable TFPI in Western blots.

Conclusions—

GPI-anchored TFPI is the predominant form on placental endothelium. Heparin-releasable TFPI likely represents only a small portion of the total TFPI on endothelium that remains attached to cell-surface glycosaminoglycans after cleavage of the GPI anchor by endogenous enzymes. The predominance of GPI-anchored TFPI suggests that heparin infusion does not significantly redistribute TFPI within the vasculature. The intact C-terminus in GPI-anchored TFPI indicates it is not directly attached to a GPI anchor. Rather, it most likely associates with endothelium by binding to a GPI-anchored protein.
The Reactive Adventitia
Authors: Rey Federico E. , Pagano Patrick J.
Published: December 2002

The vascular adventitia is activated in a variety of cardiovascular disease states and has recently been shown to be a barrier to nitric oxide bioactivity. Vascular fibroblasts produce substantial amounts of NAD(P)H oxidase–derived reactive oxygen species (ROS) that appear to be involved in fibroblast proliferation, connective tissue deposition, and perhaps vascular tone. However, the physiological and pathophysiological roles of the adventitia have not been extensively studied, possibly because of its location in large blood vessels remote from the vascular endothelium. In recent years, substantial information has been gathered on pathways leading to oxidase activation in smooth muscle cells and fibroblasts and the downstream signaling pathways leading to hypertrophy and proliferation. A clearer understanding of the molecular mechanisms involved will likely lead to therapeutic strategies aimed at preventing vascular dysfunction in diseases such as atherosclerosis, in which these pathways are activated.
Estrogens Inhibit Angiotensin II–Induced Leukocyte–Endothelial Cell Interactions In Vivo via Rapid Endothelial Nitric Oxide Synthase and Cyclooxygenase Activation
Authors: Álvarez Ángeles , Hermenegildo Carlos , Issekutz Andrew C. , Esplugues Juan V. , Sanz Maria-Jesus
Published: December 2002

Angiotensin II (Ang II) may be a key molecule in the development of atherosclerosis. Because the incidence of coronary atherosclerosis in premenopausal women is lower than that observed in men or postmenopausal women, we have investigated the effect of estrogens on Ang II–induced leukocyte recruitment in vivo using intravital microscopy in the rat mesenteric microcirculation. Superfusion for 60 minutes with Ang II induced a significant increase in leukocyte rolling flux, adhesion, and emigration. Administration of 17-β-estradiol (17-β-E) after 30 minutes of Ang II superfusion produced a reduction of these leukocyte responses by 55.1%, 72.7%, and 70.9%, respectively, an additional 30 minutes later. The effect observed with 17-β-E was receptor-mediated and specific. 17-β-E superfusion did not modify either L-NAME or indomethacin-induced leukocyte responses. Inhibitory responses caused by 17-β-E were not altered by either 7-nitroindazole or actinomycin D cosuperfusion. Stimulation of endothelial cells with 17-β-E caused a rapid and dose-dependent release of prostacyclin. Finally, tamoxifen or ICI 182,780 administration provoked a significant increase in leukocyte–endothelial cell interactions 90 minutes later, which were significantly attenuated by systemic preadministration with an Ang II AT
1
receptor antagonist. Tamoxifen-induced leukocyte responses were also reduced by systemic pretreatment with an anti–P-selectin mAb and an anti–CD18 mAb. Hence, the antiatherogenic effects of estrogens may be mediated by inhibition of Ang II–induced leukocyte recruitment through endothelial NO and prostacyclin release. Furthermore, scarcity of estrogens resulted in decreased levels of vasodilators and the exposure of the endothelium to the deleterious action of Ang II, which may explain the higher incidence of coronary atherosclerosis in men and postmenopausal women.
Stem Cells for Myocardial Regeneration
Authors: Orlic Donald , Hill Jonathan M. , Arai Andrew E.
Published: December 2002

Stem cells are being investigated for their potential use in regenerative medicine. A series of remarkable studies suggested that adult stem cells undergo novel patterns of development by a process referred to as transdifferentiation or plasticity. These observations fueled an exciting period of discovery and high expectations followed by controversy that emerged from data suggesting cell-cell fusion as an alternate interpretation for transdifferentiation. However, data supporting stem cell plasticity are extensive and cannot be easily dismissed. Myocardial regeneration is perhaps the most widely studied and debated example of stem cell plasticity. Early reports from animal and clinical investigations disagree on the extent of myocardial renewal in adults, but evidence indicates that cardiomyocytes are generated in what was previously considered a postmitotic organ. On the basis of postmortem microscopic analysis, it is proposed that renewal is achieved by stem cells that infiltrate normal and infarcted myocardium. To further understand the role of stem cells in regeneration, it is incumbent on us to develop instrumentation and technologies to monitor myocardial repair over time in large animal models. This may be achieved by tracking labeled stem cells as they migrate into myocardial infarctions. In addition, we must begin to identify the environmental cues that are needed for stem cell trafficking and we must define the genetic and cellular mechanisms that initiate transdifferentiation. Only then will we be able to regulate this process and begin to realize the full potential of stem cells in regenerative medicine.
Brugada Syndrome
Authors: Antzelevitch C. , Brugada P. , Brugada J. , Brugada R. , Shimizu W. , Gussak I. , Perez Riera A.R.
Published: December 2002

The Brugada syndrome has gained wide recognition throughout the world and today is believed to be responsible for 4% to 12% of all sudden deaths and ≈20% of deaths in patients with structurally normal hearts. The incidence of the disease is on the order of 5 per 10 000 inhabitants and, apart from accidents, is the leading cause of death of men under the age of 50 in regions of the world where the inherited syndrome is endemic. This minireview briefly summarizes the progress made over the past decade in our understanding of the clinical, genetic, cellular, ionic, and molecular aspects of this disease.
Novel Role of gp91
phox
-Containing NAD(P)H Oxidase in Vascular Endothelial Growth Factor–Induced Signaling and Angiogenesis
Authors: Ushio-Fukai Masuko , Tang Yan , Fukai Tohru , Dikalov Sergey I. , Ma Yuxian , Fujimoto Mitsuaki , Quinn Mark T. , Pagano Patrick J. , Johnson Chad , Alexander R. Wayne
Published: December 2002

Vascular endothelial growth factor (VEGF) induces angiogenesis by stimulating endothelial cell proliferation and migration, primarily through the receptor tyrosine kinase VEGF receptor2 (Flk1/KDR). Reactive oxygen species (ROS) derived from NAD(P)H oxidase are critically important in many aspects of vascular cell regulation, and both the small GTPase Rac1 and gp91
phox
are critical components of the endothelial NAD(P)H oxidase complex. A role of NAD(P)H oxidase in VEGF-induced angiogenesis, however, has not been defined. In the present study, electron spin resonance spectroscopy is utilized to demonstrate that VEGF stimulates O
2
·−
production, which is inhibited by the NAD(P)H oxidase inhibitor, diphenylene iodonium, as well as by overexpression of dominant-negative Rac1 (N17Rac1) and transfection of gp91
phox
antisense oligonucleotides in human umbilical vein endothelial cells (ECs). Antioxidants, including
N
-acetylcysteine (NAC), various NAD(P)H oxidase inhibitors, and N17Rac1 significantly attenuate not only VEGF-induced KDR tyrosine phosphorylation but also proliferation and migration of ECs. Importantly, these effects of VEGF are dramatically inhibited in cells transfected with gp91
phox
antisense oligonucleotides. By contrast, ROS are not involved in mediating these effects of sphingosine 1-phosphate (S1P) on ECs. Sponge implant assays demonstrate that VEGF-, but not S1P-, induced angiogenesis is significantly reduced in wild-type mice treated with NAC and in gp91
phox−/−
mice, suggesting that ROS derived from gp91
phox
-containing NAD(P)H oxidase play an important role in angiogenesis in vivo. These studies indicate that VEGF-induced endothelial cell signaling and angiogenesis is tightly controlled by the reduction/oxidation environment at the level of VEGF receptor and provide novel insights into the NAD(P)H oxidase as a potential therapeutic target for angiogenesis-dependent diseases.
Apoptosis and Cellular Activation in the Pathogenesis of Acute Vascular Rejection
Authors: Holzknecht Zoie E. , Kuypers Karisha L. , Plummer Timothy B. , Williams Josie , Bustos Matilda , Gores Gregory J. , Brunn Gregory J. , Platt Jeffrey L.
Published: December 2002

Acute vascular or humoral rejection, a vexing outcome of organ transplantation, has been attributed by some to activation and by others to apoptosis of endothelial cells in the graft. We asked which of these processes causes acute vascular rejection by tracing the processes during the development of acute vascular rejection in porcine cardiac xenografts performed in baboons. Apoptosis, assayed by terminal deoxynucleotidyl transferase–mediated dUTP nick end-labeling (TUNEL), expression of activated caspase-3, and proapoptotic genes Bax and Bcl-x
L
, was not detected until acute vascular rejection was well advanced, and even then, apoptosis was largely confined to myocytes. Activation of the endothelium, as evidenced by expansion of rough endoplasmic reticulum and increased ribosomal antigen and phospho-p70 S6 kinase, occurred early in the course of acute vascular rejection and progressed through the disease process. These findings suggest that acute vascular rejection is caused by an active metabolic process and not by apoptosis in the endothelium.
Defect in Microvascular Adaptation to Chronic Changes in Blood Flow in Mice Lacking the Gene Encoding for Dystrophin
Authors: Loufrani Laurent , Levy Bernard I. , Henrion Daniel
Published: December 2002

Dystrophin has a key role in striated muscle mechanotransduction. In mice lacking the gene encoding for dystrophin (mdx mice), the absence of dystrophin and several other proteins of the dystrophin-glycoprotein complex induces a defect in flow (shear stress)–mediated NO-dependent dilation (FMD). Because the endothelium is essential for the adaptation of arteries to chronic changes in blood flow, the long-term consequences of this vascular deficiency might affect flow-induced vascular remodeling. Thus, we submitted mouse mesenteric resistance arteries to chronic changes in flow by alternatively ligating arteries. Arteries were thus submitted to high flow (HF), low flow (LF), or normal flow. After 2 weeks, arteries were studied in vitro in an arteriograph. Increases in diameter (from 174±10 to 210±15 μm, pressure 75 mm Hg) found in HF arteries were not significant in mdx mice. Arterial diameters in LF arteries decreased similarly in control and mdx mice. FMD increased in HF arteries and decreased in LF arteries. FMD was not increased in HF arteries in mdx mice. NO-dependent FMD and NO synthase expression increased in the HF arteries of control mice but not in those of mdx mice. Dilatory and contractile tone, depending on the smooth muscle, was unaffected in HF arteries but decreased in LF arteries of both strains. We conclude that resistance arteries of mdx mice do not adapt properly to chronic changes in flow, inasmuch as the increases in diameter, endothelial NO synthase expression, and FMD did not occur in mdx mice submitted to HF for 2 weeks. This study suggests that blood flow regulation might be disturbed in dystrophin-related myopathies, possibly increasing organ damage.
Cardiomyocyte Cultures With Controlled Macroscopic Anisotropy
Authors: Bursac N. , Parker K.K. , Iravanian S. , Tung L.
Published: December 2002

Structural and functional cardiac anisotropy varies with the development, location, and pathophysiology in the heart. The goal of this study was to design a cell culture model system in which the degree, change in fiber direction, and discontinuity of anisotropy can be controlled over centimeter-size length scales. Neonatal rat ventricular myocytes were cultured on fibronectin on 20-mm diameter circular cover slips. Structure-function relationships were assessed using immunostaining and optical mapping. Cell culture on microabraded cover slips yielded cell elongation and coalignment in the direction of abrasion, and uniform, macroscopically continuous, elliptical propagation with point stimulation. Coarser microabrasion (wider and deeper abrasion grooves) increased longitudinal (23.5 to 37.2 cm/s;
r
=0.66) and decreased transverse conduction velocity (18.1 to 9.2 cm/s;
r
=−0.84), which resulted in increased longitudinal-to-transverse velocity anisotropy ratios (1.3 to 3.7, n=61). A thin transition zone between adjacent uniformly anisotropic areas with 45° or 90° difference in fiber orientation acted as a secondary source during 2× threshold field stimulus. Cell culture on cover slips micropatterned with 12- or 25-μm wide fibronectin lines and previously coated with decreasing concentrations of background fibronectin yielded transition from continuous to discontinuous anisotropic architecture with longitudinally oriented intercellular clefts, decreased transverse velocity (16.9 to 2.6 cm/s;
r
=−0.95), increased velocity anisotropy ratios (1.6 to 5.6, n=70), and decreased longitudinal velocity (36.4 to 14.6 cm/s;
r
=−0.85) for anisotropy ratios >3.5. Cultures of cardiac myocytes with controlled degree, uniformity and continuity of structural, and functional anisotropy may enable systematic 2-dimensional in vitro studies of macroscopic structure-related mechanisms of reentrant arrhythmias. The full text of this article is available at http://www.circresaha.org.
Control of Cajal body number is mediated by the coilin C-terminus
Authors: Shpargel Karl B. , Ospina Jason K. , Tucker Karen E. , Matera A. Gregory , Hebert Michael D.
Published: December 2002

Cajal bodies (CBs) are nuclear suborganelles implicated in the post-transcriptional maturation of small nuclear and small nucleolar RNAs. The number of CBs displayed by various cell lines and tissues varies, and factors that control CB numbers within a given cell have yet to be described. In this report, we show that specific regions within the C-terminus of coilin, the CB marker protein, are responsible for regulating the number of nuclear foci. Despite the fact that the coilin N-terminal domain is responsible for its self-oligomerization activity, truncation or mutation of predicted sites of phosphorylation in the conserved C-terminal region leads to a striking alteration in the number of nuclear bodies. Similarly, coilin constructs from various species display differential propensities to form nuclear foci when expressed in heterologous backgrounds. We mapped the domain responsible for this variability to the coilin C-terminus utilizing chimeric proteins. Furthermore, the activities responsible for regulating coilin self-association must reside in the nucleus, as constructs lacking critical nuclear localization sequences fail to form foci in the cytoplasm. Factors controlling the putative signal transduction cascade that phosphorylates coilin are also discussed. The results point to a model whereby phosphorylation of the coilin C-terminus regulates the availability of the N-terminal self-interaction domain.
Secretory ribonucleases are internalized by a dynamin-independent endocytic pathway
Authors: Haigis Marcia C. , Raines Ronald T.
Published: December 2002

Cytosolic internalization is a requirement for the toxicity of secretory ribonucleases. Here, we investigate the mechanism of internalization of Onconase® (ONC), a toxic protein, and ribonuclease A (RNase A), a nontoxic homolog. Microscopy studies indicate that both ribonucleases readily bind to the cell surface and are internalized via acidic vesicles. Blocking dynamin-dependent endocytosis prevents transferrin internalization but does not hinder RNase A internalization. ONC and G88R RNase A, which is a toxic variant, demonstrate enhanced cytotoxicity in the absence of clathrin- and dynamin-mediated endocytosis. The cytosolic entry of ribonucleases does not require an acidic environment or transport to the ER and probably occurs from endosomes. Thus, common proteins — secretory ribonucleases — enter the cytosol by a pathway that is distinct from that of other known toxins.
Differential usage of two in-frame translational start codons regulates subcellular localization ofArabidopsis thalianaTHI1
Authors: Chabregas Sabrina M. , Luche Douglas D. , Van Sluys Marie-Anne , Menck Carlos F. M. , Silva-Filho Marcio C.
Published: December 2002

Arabidopsis thaliana THI1 is encoded by a single nuclear gene and directed simultaneously to mitochondria and chloroplasts from a single major transcript. In vitro transcription/translation experiments revealed the presence of two translational products by the differential usage of two in-frame translational start codons. The coupling site-specific mutations on the THI1 encoding sequence with green fluorescent protein (GFP) gene fusions showed that translation initiation at the first AUG directs translocation of THI1 to chloroplasts. However, when translation starts from the second AUG, THI1 is addressed to mitochondria. Analysis of the translation efficiency of thi1 mRNA revealed that the best context for translation initiation is to use the first AUG. In addition, a suboptimal context in the vicinity of the second AUG initiation codon, next to a stable stem-and-loop structure that is likely to slow translation, has been noted. The fact that translation preferentially occurs in the first AUG of this protein suggests a high requirement for TH1 in chloroplasts. Although the frequency of upstream AUG translation is higher, according to the first AUG rule, initiation at the second AUG deviates significantly from Kozak's consensus. It suggests leaky ribosomal scanning, reinitiation or the internal entry of ribosomes to assure mitochondrial protein import.
Making sense of latent TGFβ activation
Authors: Annes Justin P. , Munger John S. , Rifkin Daniel B
Published: December 2002

TGFβ is secreted as part of a latent complex that is targeted to the extracellular matrix. A variety of molecules, `TGFβ activators,' release TGFβ from its latent state. The unusual temporal discontinuity of TGFβ synthesis and action and the panoply of TGFβ effects contribute to the interest in TGF-β. However, the logical connections between TGFβ synthesis, storage and action are obscure. We consider the latent TGFβ complex as an extracellular sensor in which the TGFβ propeptide functions as the detector, latent-TGFβ-binding protein (LTBP) functions as the localizer, and TGF-β functions as the effector. Such a view provides a logical continuity for various aspects of TGFβ biology and allows us to appreciate TGFβ biology from a new perspective.
Increased Sp1 phosphorylation as a mechanism of hepatocyte growth factor (HGF/SF)-induced vascular endothelial growth factor (VEGF/VPF) transcription
Authors: Reisinger Kerstin , Kaufmann Roland , Gille Jens
Published: December 2002

Hepatocyte growth factor (HGF/SF)-induced expression of vascular endothelial growth factor (VEGF/VPF) has been implicated in paracrine amplification of angiogenesis, contributing to angiogenic responses during inflammation, wound healing, collateral formation and tumor growth. We have shown previously that HGF/SF-mediated VEGF/VPF expression by keratinocytes is primarily dependent on transcriptional activation, and we mapped the HGF/SF-responsive element to a GC-rich region between bp -88 and -65. Sp1-like factors bind to this element constitutively; however the VEGF/VPF promoter is transactivated by HGF/SF in the absence of induced binding activity. In experimental approaches to clarify molecular mechanisms of Sp1-dependent VEGF/VPF gene transcription, neither HGF/SF-dependent changes in nuclear expression nor in relative DNA binding activity of Sp family members to the indicated element were observed. Thus, HGF/SF was hypothesized to induce VEGF/VPF gene transcription via increased transactivation activity of Sp1 owing to biochemical modification. In immunoprecipitation studies, HGF/SF was found to increase the amount of serine-phosphorylated Sp1, revealing a likely mechanism of HGF/SF-induced VEGF/VPF expression, as phosphorylation may enhance the transcriptional activity of Sp1. The contribution of different signaling molecules to HGF/SF-induced VEGF/VPF transcription was demonstrated by the use of chemical inhibition, of expression of kinase-deficient signaling proteins, and by the use of antisense oligonucleotides. Herein, we provide evidence that PI 3-kinase, MEK1/2 and PKC-ζ play a significant role in HGF/SF-induced VEGF/VPF promoter activation. Together, our results elucidate a critical pathway of paracrine amplification of angiogenesis, suggesting that HGF/SF-induced Sp1 phosphorylation may activate VEGF/VPF promoter activity that requires the contribution of distinct signaling molecules.
ANChors away: an actin based mechanism of nuclear positioning
Authors: Starr Daniel A. , Han Min
Published: December 2002

Mechanisms for nuclear migration and nuclear anchorage function together to control nuclear positioning. Both tubulin and actin networks play important roles in nuclear positioning. The actin cytoskeleton has been shown to position nuclei in a variety of systems from yeast to plants and animals. It can either act as a stable skeleton to anchor nuclei or supply the active force to move nuclei. Two C. elegans genes and their homologues play important roles in these processes. Syne/ANC-1 anchors nuclei by directly tethering the nuclear envelope to the actin cytoskeleton, and UNC-84/SUN functions at the nuclear envelope to recruit Syne/ANC-1.
Time-Resolved Total Internal Reflection Fluorometry Study on Chemical and Structural Characteristics at Water/Oil Interfaces
Authors: Ishizaka Shoji , Kitamura Noboru
Published: December 2002

Structures and characteristics of water/oil interfaces at the molecular level are reviewed. Dynamic fluorescence anisotropy of Sulforhodamine 101 (SR101) and excitation energy transfer from SR101 to Acid Blue 1 (AB1) at water/oil interfaces were studied by using time-resolved total internal reflection (TIR) fluorometry. The results indicated that a water/carbon tetrachloride (CCl4) interface was sharp with respect to the molecular size of SR101 (∼10 Å), while a water/1,2-dichloroethane (DCE) interface was relatively rough compared to the water/CCl4 interface. The present results were also compared with those predicted from molecular dynamic simulations and the thermally capillary wave theory. Furthermore, on the basis of fluorescence dynamic measurements of Sulforhodamine B (SRB) adsorbed at a water/oil interface, a relationship between thickness/roughness and the polarity at the interface was discussed.
Saccharide Effect on the Deswelling Process of the Thermosensitive Poly(N-isopropylacrylamide) Gel
Authors: Kato Norihiro , Sakai Yasuzo , Takahashi Fujio
Published: December 2002

The kinetic parameters of deswelling and the change of a lower critical solution temperature (LCST) for poly(N-isopropylacrylamide) gel, poly(NIPAAm) gel, were investigated in the presence of glucose and other sugars as hydrophilic probes. The enthalpy of activation (ΔH≠) and the entropy of activation (ΔS≠) for deswelling were influenced by the concentration of additive sugars. Plots of ΔH≠ against TΔS≠ fell on a straight line, of which the slope was approximately 0.91–0.94. This result shows a compensation effect of the free energy of activation (ΔG≠) concerning the relationship between ΔH≠ and ΔS≠ for deswelling of poly(NIPAAm) gel. The molecular interaction between sugar and water clusters involved with the polymer is responsible for the compensation effect between ΔH≠ and ΔS≠. The equatorial hydroxy groups of sugar molecules interact easily with water clusters around the hydrophobic isopropyl groups (the iceberg) to form hydrogen bonds, which give rise to change the situation of polymer hydration. A decrease of the LCST has close connections with the number of equatorial hydroxy groups of sugars as additives. The LCST decrease in sugar solutions was regarded as the situation change of polymer hydration in the iceberg.
Synthesis and Crystal Structures of Polymeric and Dimeric Forms of an Oxotitanium(IV) Complex with a Tetradentate Schiff Base Ligand
Authors: Tsuchimoto Masanobu
Published: December 2002

Polymeric and dimeric forms of an oxotitanium(IV) complex with a tetradentate Schiff base ligand, [TiO (salen)]·0.33CH3OH (1) (H2salen: N,N′-disalicylidene-1,2-ethanediamine) and [{TiO(salen)}2]·2DMF (2), were prepared by the reaction of the Schiff base ligand with [{TiO(acac)2}2] (H2acac: acetylacetone) in methanol and in DMF, respectively. X-ray crystal structure analyses of both complexes were carried out. Complex 1 has a linear ···Ti=O···Ti=O··· chain structure with the Ti=O and O···Ti distances being 1.705(2)–1.706(2) and 2.095(2)–2.134(2) Å, respectively. Complex 2 has a dimeric di-μ-oxo structure with the Ti–O distances being 1.804(2) and 1.907(2) Å. A strong band at 744 cm−1 in the IR spectrum of 1 was assigned unambiguously to the Ti=O stretching band by an 18O-labelling experiment.
Syntheses, Structures, and Properties of Vanadium(III) Complexes with the Hexadentate Ligand, Tetramethylenediamine-N,N,N′,N′-tetraacetate, N,N′-Bis(2-pyridylmethyl)-1,2-ethanediamine-N,N′-diacetate, and N,N′-Bis(2-pyridylmethyl)-1,3-propanediamine-N,N′-diacetate
Authors: Kanamori Kan , Kyotoh Ayako , Fujimoto Kazuya , Nagata Kiyonori , Suzuki Honoh , Okamoto Ken-ichi
Published: December 2002

Vanadium(III) complexes with the hexadentate ligand, tetramethylenediamine-N,N,N′,N′-tetraacetate (tmdta), N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine-N,N′-diacetate (bpedda), and N,N′-bis(2-pyridylmethyl)-1,3-propanediamine-N,N′-diacetate (bppdda), have been prepared. The structures of the tmdta (1) and bpedda (3) complexes have been determined by X-ray crystallography. The stereochemical property of complex 1 was compared with that of the corresponding Cr(III) complex (2), whose structure was also determined by X-ray crystallography. The tmdta complexes adopt a distorted octahedral structure, including a seven-membered chelate ring formed by the tetramethylenediamine moiety of the tmdta ligand. The bpedda complex has been determined to be a heptacoordinate complex with a distorted pentagonal bipyramidal geometry. The isolated bppdda complex has been characterized to be a μ-oxo dinuclear vanadium(III) complex on the basis of its spectral features. The tmdta and bpedda complexes do not yield a corresponding μ-oxo dinuclear vanadium(III) complex on base hydrolysis.
Temperature Dependence of the Probability of Chain Growth for Hydrocarbon Formation by Electrochemical Reduction of CO2
Authors: Ougitani Yasushi , Aizawa Tatuya , Sonoyama Noriyuki , Sakata Tadayoshi
Published: December 2002

The temperature dependence of the probability of chain growth was studied for hydrocarbons formed at Fe and Ni electrodes by electrochemical CO2 reduction. The faradaic efficiency for hydrocarbons increased with increasing temperature. The distribution of the produced hydrocarbons followed well the Schultz Flory equation. The probability of chain growth increased with increasing temperature. Based on the temperature dependence of the probability of chain growth, the mechanism of the electrochemical Fischer Tropsch reaction is discussed.
Trigonal-Bipyramidal Geometry in a Cobalt(II) Complex with an Unsymmetrical Tripodal Ligand
Authors: Lim Jong-Wan , Mikuriya Masahiro , Sakiyama Hiroshi
Published: December 2002

A cobalt(II) complex with bis[2-(3,5-dimethylpyrazol-1-yl)ethyl][(pyrazol-1-yl)methyl]amine (bppa), [CoCl(bppa)][B(C6H5)4]·C2H5OH, was synthesized and characterized by measurements of the magnetic moment and the electronic spectra. The X-ray crystal structure shows that the compound has a distorted trigonal bipyramid with a N4Cl coordination environment.
Aqueous Micellar Medium in Organic Synthesis: Alkylations and Michael Reactions of Benzotriazole
Authors: Mashraqui Sabir Hussain , Kumar Sukeerthi , Mudaliar Chandrasekhar Dayal
Published: December 2002

The feasibility of aqueous micelles of cetyltrimethylammonium bromide in catalyzing C–N bond formation has been studied with respect to N-alkylations of benzotriazole (Bt). Alkylations with various alkylating agents and the addition of Bt across activated double bonds in the Michael fashion occurred successfully in fair-to-good yields in the aqueous micellar regime. These reactions provided a mixture of N-1 and N-2 alkylated products, with a marked preference for N-1 over N-2 isomers. Micellar catalysis has been evaluated experimentally to indicate over a 50% micellar contribution to these alkylations in contrast to their aqueous counterparts. Since, N-alkyl benzotriazoles are of potential biological interest, the present micellar procedure offers a convenient alternative to other available methods.
Highly Enantioselective Cyclopropanation of Styrenes and Diazoacetates Catalyzed by 3-Oxobutylideneaminatocobalt(II) Complexes, Part 1. Designs of Cobalt Complex Catalysts and the Effects of Donating Ligands
Authors: Ikeno Taketo , Sato Mitsuo , Sekino Hiroyuki , Nishizuka Asae , Yamada Tohru
Published: December 2002

Highly enantioselective cyclopropanation of styrene derivatives and diazoacetates was effectively catalyzed by reasonably designed 3-oxobutylideneaminatocobalt(II) complexes, whose ligands were prepared from 1,2-dimesitylethylenediamine and alkyl 3-oxobutanoates. The steric demand of the diamine unit of the complexes seriously influenced the enantioselectivity, and the ester groups on their side chains somewhat improved the trans-selectivity. Addition of a catalytic amount of N-methylimidazole significantly accelerated the reaction and enhanced the enantioselectivity due to its coordination to the center cobalt atom of the complex as an axial ligand. Alcoholic or aqueous alcoholic solvents were also effective particularly for the cyclopropanation of 1-substituted 1-phenylethylenes to achieve high enantioselectivity in aqueous methanol.
Highly Enantioselective Cyclopropanation of Styrenes and Diazoacetates Catalyzed by 3-Oxobutylideneaminatocobalt(II) Complexes, Part 2. Semiempirical Analysis of Diastereo and Enantioselectivities
Authors: Ikeno Taketo , Iwakura Izumi , Yamada Tohru
Published: December 2002

A semiempirical analysis using the PM3(tm) method was performed on the 3-oxobutylideneaminatocobalt(II) complexes-catalyzed cyclopropanation. Although the energy diagram calculated by the PM3(tm) method had a contradiction, where the product was less stable than the reactant, the structures and the energies of the reactant and the transition state obtained by the PM3(tm) method could be relatively reliable by comparing with the results based on the density functional theory. Analysis of the transition states by the PM3(tm) method indicated that the olefin approached parallel to the cobalt-carbene bond with bisecting an O1–Co–O2 angle. It was revealed that the transition state affording the (1S,2S)-arylcyclopropanecarboxylic acid ester corresponding to the (1S,2S)-cobalt complex was the most stable, because of the lowest steric repulsion among the aryl group of the diamine unit, the ester moiety, and the approaching olefin. It was clarified that the enantioselectivity occurred due to the repulsion between the aryl group of the diamine unit and the ester moiety and that the diastereoselectivity was controlled by the repulsion between the ester moiety and the approaching olefin.
Spectroscopic and Product Studies of the Effect of Para Substituents on the Reactivity of Triplet Bis(2,6-dimethylphenyl)carbenes
Authors: Hu Yingmo , Ishikawa Yui , Hirai Katsuyuki , Tomioka Hideo
Published: December 2002

A series of diazobis(2,6-dimethylphenyl)methanes (1) bearing eight symmetrical para di-substituents have been prepared and photolyzed to generate the corresponding carbenes (2). Product analysis studies showed that carbenes (2) decay mainly either by dimerization to form tetra(aryl)ethylene (3) or by attack at an o-methyl group to afford 1,2-dihydrobenzocyclobutenes (4) by way of o-quinodimethanes (6) in solution. The zero-field splitting parameters, D and E, were measured in matrices of different viscosities and are analyzed in terms of a sigma-dot (σ•) scale of spin-delocalization substituent constants. Fairly good correlation with σ• was found for the D values of 32 in its minimum energy geometry. Stabilities of 32 were estimated either by measuring the temperature at which the triplet carbene signals disappeared upon thawing the matrix or by analyzing the decay kinetics of 32 in a degassed solution at room temperature. They are examined in terms of the D values in matrix at low temperature and in terms of product distributions in solution at room temperature.
Calorimetric Investigations of Phase Transitions Occurring in Molecule-Based Materials in Which Electrons Are Directly Involved
Authors: Sorai Michio
Published: December 2002

New types of phase transitions occurring in molecule-based materials have recently drawn great attention, in which electrons are directly involved. In this paper are given calorimetric investigations aimed at the elucidation of the mechanisms governing such phase transitions as (i) spin crossover phenomena occurring between high- and low-spin states in transition-metal complexes, (ii) intramolecular electron transfers in mixed-valence complexes, (iii) neutral-to-ionic transitions due to charge transfer mechanism, and (iv) thermochromic phenomena due to a change in coordination geometry. Since a change in the electronic state is strongly coupled with a change in the lattice, it turns out that the transition mechanisms always include interplays with various molecular motions in the lattice. In all these systems, a large change in the electronic energy is compensated by the entropy term due to these molecular motions.
The Surface Reaction Mechanism on Al(111)
Authors: Nakajima Tohru , Yamashita Koichi
Published: December 2002

A surface reaction mechanism in the aluminum chemical vapor deposition (Al-CVD) method using dimethylaluminum hydride (DMAH) as the material gas has been studied using quantum chemical methods. Density functional theory (DFT) and a cluster model were used to calculate the potential energies and the structures of adsorbates and transition states of surface reactions. We have obtained the result that the hydrogen molecule and trimethylaluminum (TMA) are easily produced, while methane cannot be formed as a reaction product of Al-CVD because of the large barrier height, although the latter reaction path is thermodynamically accessible.
New Interpretation of the Transfer Coefficient in Electrochemistry
Authors: Sakata Tadayoshi , Nakamura Hideo
Published: December 2002

A new theory and interpretation of the transfer coefficient based on electrostatic screening of the electrode potential is proposed. A new theory constructed based on the Debye–Hückel theory could quantitatively explain the dependence of transfer coefficient on the ionic strength of the electrolyte solution. The experimental results of the transfer coefficient for hydrogen evolution and Fe3+ / Fe2+ redox reactions were analyzed by this theory. It demonstrates that the transfer coefficient represents the electrostatic screening of the electrode potential by ions in the electrolyte solution near to the electrode. It is also shown theoretically that the information on the “electron transfer distance” is contained in the transfer coefficient.
Radicals in the Mechanochemical Dechlorination of Hazardous Organochlorine Compounds Using CaO Nanoparticles
Authors: Ikoma Tadaaki , Zhang Qiwu , Saito Fumio , Akiyama Kimio , Tero-Kubota Shozo , Kato Tatsuhisa
Published: December 2002

For the first time, we detected paramagnetic products generated during the grinding of 3-chlorobiphenyl (BP-Cl) with calcium oxide (CaO) nanoparticles by a ball mill method, which is one of the promising ways to detoxify hazardous chlorinated organic compounds. Those products were assigned to oxygen-centered aromatic radicals coming from BP-Cl and trapped electrons in oxygen vacancies on the surfaces of the CaO reactants using high-frequency and pulsed electron paramagnetic resonance spectroscopies. The observed good correlation between the dechlorination efficiency and the radical yield suggests that a radical mechanism plays an important role in the destruction of organochlorine compounds. The mechanochemical dechlorination could be interpreted by the following mechanism. First of all, the mechanical stressing induces the electron transfer from O2− sites on the surface of the CaO particle to the organic compounds. The produced organic anion radicals then undergo the effective self-dissociation of a chlorine–carbon bond.