bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Biofilm Formation and Motility Associated with Lipopolysaccharide/Exopolysaccharide-Coupled Biosynthetic Genes inStenotrophomonas maltophilia
Authors: Huang Tzu-Pi , Somers Eileen B. , Wong Amy C. Lee
Published: April 2006

Stenotrophomonas maltophiliaWR-C is capable of forming biofilm on polystyrene and glass. The lipopolysaccharide/exopolysaccharide-coupled biosynthetic genesrmlA,rmlC, andxanBare necessary for biofilm formation and twitching motility. Mutants with mutations inrmlACandxanBdisplay contrasting biofilm phenotypes on polystyrene and glass and differ in swimming motility.
An Allele of
gyrA
Prevents
Salmonella enterica
Serovar Typhimurium from Using Succinate as a Carbon Source
Authors: Schmitz George E. , Downs Diana M.
Published: April 2006

A mutant
gyrA
allele resulting in an A271E substitution in the DNA gyrase protein generated a strain unable to grow on the C
4
-dicarboxylates succinate, malate, and fumarate. Bacteria harboring
gyrA751
displayed decreased negative supercoiling in cells. Expression of the
dctA
gene, which encodes the C
4
-dicarboxylate transporter, was reduced in a
gyrA751
mutant, providing the first evidence that
dctA
expression is supercoiling sensitive and uncovering a simple metabolic screen for lesions in gyrase that reduce negative supercoiling.
BacA-Mediated Bleomycin Sensitivity in
Sinorhizobium meliloti
Is Independent of the Unusual Lipid A Modification
Authors: Ferguson Gail P. , Jansen An , Marlow Victoria L. , Walker Graham C.
Published: April 2006

Sinorhizobium meliloti bacA
mutants are symbiotically defective, deoxycholate sensitive, and bleomycin resistant. We show that the bleomycin resistance phenotype is independent of the lipid A alteration and that the changes giving rise to both phenotypes are likely to be involved in the inability of
bacA
mutants to persist within their hosts.
A framework for a phylogenetic classification in the genus Cortinarius (Basidiomycota, Agaricales) derived from morphological and molecular data
Authors: Garnica Sigisfredo , Weiß Michael , Oertel Bernhard , Oberwinkler Franz
Published: April 2006

Phylogenetic relationships in the genus Cortinarius with emphasis on European species were studied by integrating a molecular phylogenetic analysis of nuclear rDNA sequences with morphological, chemical, and ecological data. Internal transcribed spacers (ITS1 and ITS2, including 5.8S) and the D1–D2 regions of nuclear rDNA of 262 Cortinarius species including most of the recognised subgenera from Europe, South America, Australia, Tasmania, New Zealand, and Asia were sequenced and analysed by maximum likelihood and neighbour joining. Our morphological and molecular analyses showed considerable disagreement with earlier morphology-based hypotheses concerning the infrageneric delimitations in Cortinarius. We propose a new base for a more natural classification system in Cortinarius involving the taxonomic rearrangement of the species into the following major lineages that we informally designate as “clades” at this time: (1) phlegmacioid species are included in Alluti, Amarescentes, Arguti, Calochroi, Caerulescentes, Percomes, Phlegmacioides, Phlegmacium, Purpurascentes, Scauri, and Vulpini; (2) the Heterocliti clade includes species of the subgenera Leprocybe and Cystogenes ; (3) most of the Myxacium species are included in the Delibuti and Myxacium clades; (4) part of Rozites are included in the Rozites clade; (5) the north-hemispheric species of subgenus Dermocybe are included in the Dermocybe clade and part of the south-hemispheric species in the Splendidi clade; (6) part of Sericeocybe are integrated in the Anomali and Telamonia clades; (7) members of subgenus Cortinarius are assigned to the Cortinarius clade; (8) telamonioid taxa are included in the Obtusi, Renidentes, and Telamonia clades. Several Cortinarius species with peculiar patterns of morphology and basidiome coloration had isolated positions in the sequence analysis, and the evolutionary relationships among the major lineages remained unresolved. Our results suggest the convergent evolution of certain morphological traits across phylogenetically divergent lineages in Cortinarius. However, combinations of features such as pileipellis anatomy, spore shape, veil coloration, basidiome pigments, and stipe shape appear useful to circumscribe clades. Our molecular phylogenetic analysis allows insights in global geographical patterns of species distribution within the major lineages in the genus Cortinarius. The clade structure proposed here could be used as backbone for further more detailed systematic studies.
Seasonal pattern of leaf production and its effects on assimilation in giant summer-green herbs in deciduous forests in northern Japan
Authors: Tani Tomokazu , Kudo Gaku
Published: April 2006

Understory vegetation of northern deciduous forests in far eastern Asia is characterized by giant summer-green herbs. We examined the patterns of height growth, leaf accumulation, photosynthetic characteristics, daily net assimilation, and dry matter allocation within aboveground parts of six giant summer-green herbs with reference to light conditions in deciduous forests. Plant height, leaf number, and total leaf area per plant increased with progressing tree-canopy closure in five species ( Cacalia hastata L. subsp. orientalis Kitam., Cirsium kamtschaticum Ledeb., Filipendula kamtschatica (Pall.) Maxim. f. kamtschatica, Senecio cannabifolius Less., and Urtica platyphylla Wedd.) that had continuous leaf production throughout the growing season, whereas one species ( Veratrum album L. subsp. oxysepalum Hulten) with early leaf production, completed leaf production mostly before the beginning of tree-canopy closure. Maximum photosynthetic and dark respiration rates decreased seasonally in all species. Species with continuous leaf emergence accumulated leaves acclimatized to shade conditions, which offset the decreasing photosynthesis of individual leaves with progressing tree-canopy closure, resulting in stable carbon gain even under decreasing light availability. In contrast, V. album assimilated vigorously during the short period of high irradiance before tree-canopy closure, and decreased its assimilation rate continuously thereafter.
A new invasive hawkweed, Hieracium glomeratum (Lactuceae, Asteraceae), in the Pacific Northwest
Authors: Wilson Linda M. , Fehrer Judith , Bräutigam Siegfried , Grosskopf Gitta
Published: April 2006

During the summer of 2001, a newly recorded species of exotic hawkweed ( Hieracium glomeratum Froel.) for North America was identified from specimens collected in southeastern British Columbia, Canada, and eastern Washington state, United States. The specimens had previously been identified as the closely related Hieracium caespitosum Dumort. DNA fingerprints of plants from different localities proved to be identical. Their clonality, along with a spot-like distribution, indicates that this apomictic species probably originated from a single introduction from Europe, which subsequently spread. This species adds to the complex of 14 other exotic Hieracium species belonging to the Eurasian subgenus Pilosella that are adventive in the United States and Canada. A distribution map of the native and adventive range of H. glomeratum, and a key to distinguish it from related species in subgenus Pilosella that occur in North America are provided. The evolutionary and invasive potential of H. glomeratum is also discussed.
Functional differentiation in pollination processes between the outer and inner perianths in Iris gracilipes (Iridaceae)
Authors: Morinaga Shin-Ichi , Sakai Satoki
Published: April 2006

We examined the functional differentiation in pollination processes between the outer and inner perianths in Iris gracilipes A. Gray flowers. We manipulated the length of the outer and inner perianths and examined the effect on the following: number of pollinator approaches to, and landings on, flowers; pollen removal and deposition during a single pollinator visit; total number of pollen grains removed; and seed production. The outer perianths contributed to the functions of pollinator approach and landing, pollen removal, and seed production, but not to mechanical fitting of pollinators. Since flowers with shortened outer perianths gained less pollination success than control flowers, and since lengthening of outer perianths did not enhance pollination success, the length of the outer perianths might have evolved as an adaptive characteristic. On the other hand, the inner perianths contributed to the functions of pollinator approach and pollen removal but not to pollinator landing, mechanical fitting of pollinators, nor seed production. Since flowers with shortened inner perianths gained pollination success similar to that of control flowers, the adaptive length of the inner perianths may be shorter than what is found in present-day flowers. We propose that genetic correlation between the outer and the inner perianths might prevent shortening of the inner perianths.
Plant bioactive peptides: an expanding class of signaling molecules
Authors: Germain Hugo , Chevalier Eric , Matton Daniel P.
Published: April 2006

Until recently, our knowledge of intercellular signaling in plants was limited to the so-called five classical plant hormones: auxin, cytokinin, gibberellin, ethylene, and abscissic acid. Other chemical compounds like sterols and lipids have also been recognized as signaling molecules in plants, but it was only recently discovered that peptides in plants, as in animal cells, play crucial roles in various aspects of growth and development, biotic and abiotic stress responses, and self/non-self recognition in sporophytic self-incompatibility. These peptides are often part of a very large gene family whose members show diverse, sometime overlapping spatial and temporal expression patterns, allowing them to regulate different aspects of plant growth and development. Only a handful of peptides have been linked to a bona fide receptor, thereby activating a cascade of events. Since these peptides have been thoroughly reviewed in the past few years, this review will focus on the small putative plant signaling peptides, some often disregarded in the plant peptide literature, which have been shown through biochemical or genetic studies to play important roles in plants.
Effects of pollinators and flower bud herbivores on reproductive success of two ericaceous woody species differing in flowering season
Authors: Osada Noriyuki , Sugiura Shinji
Published: April 2006

To investigate the relative importance of pollinators and flower bud herbivores on final fruit set, the ratios of flower to flower bud (flower/bud), fruit to flower (fruit/flower), and fruit to flower bud (fruit/bud) were examined for the two bumble-bee-pollinated ericaceous species that have different flowering seasons: Pieris japonica (Thunb.) D. Don produces flower buds in autumn and blooms in early spring, whereas Lyonia ovalifolia (Wall.) Drude produces flower buds and blooms in late spring. Floral longevity was longer in P. japonica than in L. ovalifolia, and bagged flowers had an even longer floral longevity. The fruit/flower ratio was similar between the cross-pollinated and control flowers in P. japonica, but was smaller in control flowers than in cross-pollinated flowers in L. ovalifolia. Despite unpredictable pollinator activity in early spring, long flowering duration and no competition for pollinators facilitated reproductive success of P. japonica. In contrast, short flowering duration and severe competition for pollinators limited the reproductive success of L. ovalifolia. Flower bud herbivory was more severe in P. japonica than in L. ovalifolia. In both species, predispersal seed herbivores were negligible. Consequently, the fruit/bud ratio was mainly affected by the flower/bud ratio in P. japonica and by the fruit/flower ratio in L. ovalifolia. Our results suggest that despite intense herbivory of flower buds, early spring flowering of P. japonica facilitates pollination because of less competition for pollinators in comparison to L. ovalifolia. Thus, the relative importance of pollinators and herbivores on fruit set differs between the two studied species that differ in flowering periods.
A three-dimensional slope stability problem in clay
Authors: Silvestri Vincenzo
Published: April 2006

A three-dimensional slope stability problem involving a spherical failure surface in clay is often used in the literature as a benchmark example against which numerical models are validated. The factor of safety, which is used as a reference value, has been found to be inaccurate. This technical note shows how to obtain the correct value for the factor of safety and compares the result with those given by some numerical models used in practice.Key words: three-dimensional slope stability analysis, clay, undrained shear strength, factor of safety, spherical failure surface, comparisons.
Long-term monitoring of SIDD Type IV installations
Authors: Wong Lui S , Allouche Erez N , Dhar Ashutosh S , Baumert Michael , Moore Ian D
Published: April 2006

An evaluation of the standard installation direct design (SIDD) prediction method has been undertaken by constructing and monitoring full-scale test beds installed according to SIDD Type IV specifications at four test sites across southern Ontario, Canada. Stresses around the test beds were monitored over a period of 20 months. The internal diameter of the test pipe segments varied from 600 mm to 900 mm; in situ soil conditions ranged from organic clay to sand, and burial depths varied from 1.5 to 3 times the diameter of the installed pipe. All test sections were subjected to frequent heavy traffic loads, representing a worse case loading scenario. Measurements from the 20 month monitoring period were compared with predictions from Ontario Provincial Standards and SIDD specifications. It was concluded that the SIDD method reasonably predicts the stress envelope around a buried rigid pipe installed using the cut-and-cover construction method. The indirect design method currently used by the Ontario Provincial Standards was found to provide an overly conservative prediction of soil stresses at the invert of the pipe. Field measurements also suggest that the value of the horizontal arching factor (HAF) currently recommended by SIDD for Type IV installations is overly conservative and can be increased while maintaining a conservative design approach.Key words: soil, pipe, interaction, rigid, SIDD, monitoring.
The residual shear strength of tropical soils
Authors: Rigo Marcelo Luvison , Pinheiro Rinaldo José Barbosa , Bressani Luiz Antônio , Bica Adriano Virgílio Damiani , Silveira Rodrigo Moraes da
Published: April 2006

The paper discusses the residual shear strength of tropical soils. Ring shear tests have been performed with tropical soils from southern Brazil using the Bromhead apparatus. The data from the study are compared with data obtained in a comprehensive literature review of the subject. The residual friction angle of tropical residual soils from sedimentary formations decreases with increasing plasticity index following a general trend presented in the literature. Most of the residual soils described herein have also shown this trend. However, some of these residual soils, particularly basalt saprolitic soils, have shown quite low residual friction angles despite having low plasticity index and clay fraction values. It has been confirmed that the residual shear strength of tropical soils depends chiefly on mineralogy, particle size distribution, effective stress, parent rock, weathering degree, pedogenetic evolution and - when partly weathered minerals are present - degradation upon shearing. The substantial range of new data shown in the paper has allowed the definition of general boundaries of different soil behaviour in a chart of residual friction angle versus plasticity index. Each region has been associated with a different type of tropical soil.Key words: tropical soils, residual soils, residual shear strength, laboratory tests.
APPROXIMATE BLOCK SORTING
Authors: MAHAJAN MEENA , RAMA RAGHAVAN , RAMAN VENKATESH , VIJAYKUMAR S.
Published: April 2006

We consider the problem BLOCK-SORTING: Given a permutation, sort it by using a minimum number of block moves, where a block is a maximal substring of the permutation which is also a substring of the identity permutation, and a block move repositions the chosen block so that it merges with another block. Although this problem has recently been shown to be NP-hard [3], nothing better than a trivial 3-approximation was known. We present here the first non-trivial approximation algorithm to this problem. For this purpose, we introduce the following optimization problem: Given a set of increasing sequences of distinct elements, merge them into one increasing sequence with a minimum number of block moves. We show that the merging problem has a polynomial time algorithm. Using this, we obtain an O(n3) time 2-approximation algorithm for BLOCK-SORTING.

We also observe that BLOCK-SORTING, as well as sorting by transpositions, are fixed-parameter-tractable in the framework of [6].
Cardiac aquaporin expression in humans, rats, and mice
Authors: Butler Tanya L. , Au Carol G. , Yang Baoxue , Egan Jonathan R. , Tan Yee Mun , Hardeman Edna C. , North Kathryn N. , Verkman A. S. , Winlaw David S.
Published: April 2006

Water accumulation in the heart is important in ischemia-reperfusion injury and operations performed by using cardiopulmonary bypass, with cardiac dysfunction associated with myocardial edema being the principal determinant of clinical outcome. As an initial step in determining the role of aquaporin (AQP) water channels in myocardial edema, we have assessed the myocardial expression of AQPs in humans, rats, and mice. RT-PCR revealed expression of AQP-1, -4, -6, -7, -8, and -11 transcripts in the mouse heart. AQP-1, -6, -7, and -11 mRNAs were found in the rat heart as well as low levels of AQP-4 and -9. Human hearts contained AQP-1, -3, -4, -5, -7, -9, -10, and -11 mRNAs. AQP-1 protein expression was confirmed by Western blot analysis in all three species. AQP-4 protein was detected in the mouse heart but not in the rat or human heart. To determine the potential functional consequences of myocardial AQP expression, water permeability was measured in plasma membrane vesicles from myocardial cells of wild-type versus various AQP knockout mice. Water permeability was reduced by AQP-1 knockout but not by AQP-4 or AQP-8 knockout. With the use of a model of isolated rat heart perfusion, it was found that osmotic and ischemic stresses are not associated with changes in AQP-1 or AQP-4 expression. These studies support a possible functional role of AQP-1 in myocardium but indicate that early adaptations to osmotic and ischemic stress do not involve transcriptional or posttranslational AQP-1 regulation.
Enhanced cell transplantation: preventing apoptosis increases cell survival and ventricular function
Authors: Nakamura Yoshinobu , Yasuda Tamotsu , Weisel Richard D. , Li Ren-Ke
Published: April 2006

Cell transplantation prevents cardiac dysfunction after myocardial infarction. However, because most implanted cells are lost to ischemia and apoptosis, the benefits of cell transplantation on heart function could be improved by increasing cell survival. To examine this possibility, male Lewis rat aortic smooth muscle cells (SMCs; 4 × 106) were pretreated with antiapoptotic Bcl-2 gene transfection or heat shock and then implanted into the infarcted myocardium of anesthetized, syngenic female rats ( n = 23 per group). On the first day after transplantation, apoptotic SMCs were quantified by using transferase-mediated dUTP nick-end labeling staining. On days 7 and 28, grafted cell survival was quantified by using real-time PCR, and heart function was assessed with the use of echocardiography and the Langendorff apparatus. SMCs given antiapoptotic pretreatments exhibited improvements in each measure relative to controls. Apoptosis was reduced in Bcl-2-treated cells relative to all other groups ( P < 0.05), whereas survival ( P < 0.01) was increased. Heat shock also significantly decreased apoptosis and increased survival relative to control groups ( P < 0.05 for group effect), although these effects were less pronounced than in the Bcl-2-treated group. Further, scar areas were reduced in both Bcl-2- and heat shock-treated groups relative to controls ( P < 0.05), and fractional area change and cardiac function were greater ( P < 0.05 for both measures). These results indicate that antiapoptosis pretreatments reduced grafted SMC loss after transplantation and enhanced grafted cell survival and ventricular function, which was directly related ( r = 0.72; P = 0.002) to the number of surviving engrafted cells.
Alveolar hypoxia induces left ventricular diastolic dysfunction and reduces phosphorylation of phospholamban in mice
Authors: Larsen Karl-Otto , Sjaastad Ivar , Svindland Aud , Krobert Kurt A. , Skjønsberg Ole Henning , Christensen Geir
Published: April 2006

Chronic obstructive pulmonary disease (COPD) may lead to pulmonary hypertension (PH) and reduced function of the right ventricle (RV). However, COPD patients may also develop left ventricular (LV) diastolic dysfunction. We hypothesized that alveolar hypoxia induces LV diastolic dysfunction and changes in proteins governing Ca2+removal from cytosol during diastole. Mice exposed to 10% oxygen for 1, 2, or 4 wk were compared with controls. Cardiac hemodynamics were assessed with Doppler echocardiography and a microtransducer catheter under general anesthesia. The pulmonary artery blood flow acceleration time was shorter and RV pressure was higher after 4 wk of hypoxia compared with controls (both P < 0.05). In the RV and LV, 4 wk of hypoxia induced a prolongation of the time constant of isovolumic pressure decay (51% RV, 43% LV) and a reduction in the maximum rate of decline in pressure compared with control (42% RV, 42% LV, all P < 0.05), indicating impaired relaxation and diastolic dysfunction. Alveolar hypoxia induced a 38%, 47%, and 27% reduction in Ser16-phosphorylated phospholamban (PLB) in the RV after 1, 2, and 4 wk of hypoxia, respectively, and at the same time points, Ser16-phosphorylated PLB in the LV was downregulated by 32%, 34%, and 25% (all P < 0.05). The amounts of PLB and sarco(endo)plasmic reticulum Ca2+ATPase (SERCA2a) were not changed. In conclusion, chronic alveolar hypoxia induces hypophosphorylation of PLB at Ser16, which might be a mechanism for impaired relaxation and diastolic dysfunction in both the RV and LV.
Cardioprotective effects of rosiglitazone are associated with selective overexpression of type 2 angiotensin receptors and inhibition of p42/44 MAPK
Authors: Molavi Behzad , Chen Jiawei , Mehta J. L.
Published: April 2006

Current evidence points to renin-angiotensin system as a key mediator in ischemia-reperfusion injury. Rosiglitazone, a peroxisome proliferator-activated receptor-γ (PPAR-γ) ligand, has recently been shown to confer cardioprotection against ischemia-reperfusion in animal models. We sought to examine the expression of ANG II receptors during PPAR-γ-mediated cardioprotection. Male Sprague-Dawley rats (nondiabetic) were fed either regular rat chow (control diet group, n = 9) or rosiglitazone-rich diet (rosiglitazone-rich diet group, n = 9) and were subjected to 1 h of myocardial ischemia followed by 1 h of reperfusion. A third group of rats had only thoracotomy and pericardiotomy and served as a sham control group ( n = 9). Hemodynamics, infarct size, and expression of ANG II type 1 and type 2 receptors (AT1 and AT2) were measured in all groups. There was a 58% reduction of infarct size in the rosiglitazone-rich diet group ( P < 0.01 vs. control diet group). Increased myocardial expression of AT1 receptors in the ischemic-reperfused myocardium was attenuated in the rosiglitazone-rich diet group ( P < 0.05 vs. control diet group). Importantly, myocardial AT2 mRNA and protein expression were significantly increased (by >100-fold) in the rosiglitazone-rich diet group ( P < 0.05). These changes were accompanied by inhibition of p42/44 MAPK in the rosiglitazone-rich diet group, while the Akt1 expression, believed to mediate insulin sensitization, remained similar in all three groups. The cardioprotective effects of rosiglitazone against myocardial ischemia-reperfusion injury are independent of its insulin-sensitizing properties and are associated with significant overexpression of AT2 receptors along with inhibition of p42/44 MAPK.
Bile acids induce adhesion molecule expression in endothelial cells through activation of reactive oxygen species, NF-κB, and p38
Authors: Qin Pu , Tang Xiaoyan , Elloso M. Merle , Harnish Douglas C.
Published: April 2006

Bile acids are synthesized in the liver, stored in gallbladder, and secreted into the intestine to aid in the absorption of lipid-soluble nutrients. In addition, bile acids also actively participate in regulation of gene expression through their ability to act as ligands for the nuclear receptor farnesoid X receptor or by activating kinase signaling pathways. Under cholestatic conditions, elevated levels of bile acids in the liver induce hepatic inflammation, and because bile acid levels are also elevated in the circulation, they might also induce vascular inflammation. To test this hypothesis, primary human umbilical vein endothelial cells (HUVEC) and human aortic endothelial cells were treated with bile acids, and the expression of ICAM-1, VCAM-1, and E-selectin were monitored. The three major bile acids found in the circulation, chenodeoxycholic acid, deoxycholic acid, and lithocholic acid, all strongly induced both the mRNA and protein expression of ICAM-1 and VCAM-1. To delineate the mechanism, the experiments were conducted in the presence of various kinase inhibitors. The results demonstrate that the bile acid-mediated induction of adhesion molecule expression occurs by stimulation of NF-κB and p38 MAPK signaling pathways through the elevation in reactive oxygen species. The bile acid-induced cell surface expression of ICAM-1 and VCAM-1 was sufficient to result in the increased adhesion of THP-1 monocytes to the HUVEC, suggesting that elevated levels of bile acids in the circulation may cause endothelium dysfunction and contribute to the initiation of early events associated with vascular lesion formation.
Leukocyte adherence inhibits adenosine-dependent venular control of arteriolar diameter and nitric oxide
Authors: Kim Min-ho , Harris Norman R.
Published: April 2006

Venular control of arteriolar perfusion has been the focus of several investigations in recent years. This study investigated 1) whether endogenous adenosine helps control venule-dependent arteriolar dilation and 2) whether venular leukocyte adherence limits this response via an oxidant-dependent mechanism in which nitric oxide (NO) levels are decreased. Intravital microscopy was used to assess changes in arteriolar diameters and NO levels in rat mesentery. The average resting diameter of arterioles (27.5 ± 1.0 μm) paired with venules with minimal leukocyte adherence (2.1 ± 0.3 per 100-μm length) was significantly larger than that of unpaired arterioles (24.5 ± 0.8 μm) and arterioles (23.3 ± 1.3 μm) paired with venules with higher leukocyte adherence (9.0 ± 0.5 per 100-μm length). Local superfusion of adenosine deaminase (ADA) induced significant decreases in diameter and perivascular NO concentration in arterioles closely paired to venules with minimal leukocyte adherence. However, ADA had little effect on arterioles closely paired to venules with high leukocyte adherence or on unpaired arterioles. To determine whether the attenuated response to ADA for the high-adherence group was oxidant dependent, the responses were also observed in arterioles treated with 10−4 M Tempol. In the high-adherence group, Tempol fully restored NO levels to those of the low-adherence group; however, the ADA-induced constriction remained attenuated, suggesting a possible role for an oxidant-independent vasoconstrictor released from the inflamed venules. These findings suggest that adenosine- and venule-dependent dilation of paired arterioles may be mediated, in part, by NO and inhibited by venular leukocyte adherence.
Three-dimensional mechanical properties of porcine coronary arteries: a validated two-layer model
Authors: Wang Chong , Garcia Marisa , Lu Xiao , Lanir Yoram , Kassab Ghassan S.
Published: April 2006

The normal coronary artery consists of two mechanically distinct layers: intima-media and adventitia. The objective of this study is to establish a two-layer three-dimensional (3-D) stress-strain relation of porcine coronary arteries. Experimental measurements were made by a series of biaxial tests (inflation and axial extension) of intact coronary arteries and, subsequently, their corresponding intima-media or adventitia layer. The Fung-type exponential strain energy function was used to describe the 3-D strain-stress relation for each layer and the intact wall. A genetic algorithm was used to determine the material constants in the Fung-type constitutive equation by curve fitting the experimental data. Because one layer must be sacrificed before the other layer can be tested, the material property of the missing layer was computed from the material constants of the intact vessel and the tested layer. A total of 20 porcine hearts were used: one group of 10 hearts for the left anterior descending artery and another group of 10 hearts for the right coronary artery. Each group was further divided into two subgroups of five specimens tested for the intact wall and the intima-media layer and for the intact wall and the adventitia layer. Our results show statistically significant differences in the material properties of the two layers. The mathematical model was validated by experimental stress-strain data for individual layers. The validated 3-D constitutive model will serve as a foundation for formulation of layer-specific boundary value problems in coronary physiology and cardiology.
Ultrafine particulate matter exposure augments ischemia-reperfusion injury in mice
Authors: Cozzi Emily , Hazarika Surovi , Stallings Howard W. , Cascio Wayne E. , Devlin Robert B. , Lust Robert M. , Wingard Christopher J. , Van Scott Michael R.
Published: April 2006

Epidemiological studies have linked ambient particulate matter (PM) levels to an increased incidence of adverse cardiovascular events. Yet little is definitively known about the mechanisms accounting for the cardiovascular events associated with PM exposure. The goal of this study was to determine the effects of ultrafine (<0.1 μm) PM exposure on ischemia-reperfusion (I/R) injury. ICR mice were exposed to 100 μg of PM or vehicle by intratracheal instillation. Twenty-four hours later, mice were anesthetized with pentobarbital sodium (60 mg/kg), the left anterior descending coronary artery was ligated for 20 min, flow was restored for 2 h, and the resulting myocardial infarct (MI) size was evaluated. PM exposure doubled the relative size of the MI compared with the vehicle control. No difference was observed in the percentage of the left ventricle at risk for ischemia. PM exposure increased the level of oxidative stress in the myocardium after I/R. The density of neutrophils in the reperfused myocardium was increased by PM exposure, but differences in the number of blood leukocytes, expression of adhesion molecules on circulating neutrophils, and activation state of circulating neutrophils 24 h after PM exposure could not be correlated to the increased I/R injury observed. Additionally, aortas isolated from PM-exposed animals and studied in vitro exhibited a reduced endothelium-dependent relaxation response to acetylcholine. These results indicate that exposure to ultrafine PM increases oxidative stress in the myocardium, alters vascular reactivity, and augments injury after I/R in a murine model.
Profound bioenergetic abnormalities in peri-infarct myocardial regions
Authors: Hu Qingsong , Wang Xiaohong , Lee Joseph , Mansoor Abdul , Liu Jingbo , Zeng Lepeng , Swingen Cory , Zhang Ge , Feygin Julia , Ochiai Koichi , Bransford Toni L. , From Arthur H. L. , Bache Robert J. , Zhang Jianyi
Published: April 2006

Regions of myocardial infarct (MI) are surrounded by a border zone (BZ) of normally perfused but dysfunctional myocardium. Although systolic dysfunction has been attributed to elevated wall stress in this region, there is evidence that intrinsic abnormalities of contractile performance exist in BZ myocardium. This study examined whether decreases of high-energy phosphates (HEP) and mitochondrial F1F0-ATPase (mtATPase) subunits typical of failing myocardium exist in BZ myocardium of compensated postinfarct remodeled hearts. Eight pigs were studied 6 wk after MI was produced by ligation of the left anterior descending coronary artery (LAD) distal to the second diagonal. Animals developed compensated LV remodeling with a decrease of ejection fraction from 54.6 ± 5.4% to 31 ± 2.1% (MRI) 5 wk after LAD occlusion. The remote zone (RZ) myocardium demonstrated modest decreases of ATP and mtATPase components. In contrast, BZ myocardium demonstrated profound abnormalities with ATP levels decreased to 42% of normal, and phosphocreatine-to-ATP ratio (31P-magnetic resonance spectroscopy) decreased from 2.06 ± 0.19 in normal hearts to 1.07 ± 0.10, with decreases in α-, β-, OSCP, and IF1subunits of mtATPase, especially in the subendocardium. The reduction of myocardial creatine kinase isoform protein expression was also more severe in the BZ relative to the RZ myocardium. These abnormalities were independent of a change in mitochondrial content because the mitochondrial citrate synthase protein level was not different between the BZ and RZ. This regional heterogeneity of ATP content and expression of key enzymes in ATP production suggests that energetic insufficiency in the peri-infarct region may contribute to the transition from compensated LV remodeling to congestive heart failure.
The high-affinity IgE receptor (FcεRI): a critical regulator of airway smooth muscle cells?
Authors: Gounni Abdelilah Soussi
Published: April 2006

The airway smooth muscle (ASM) has been typically described as a contractile tissue, responding to neurotransmitters and inflammatory mediators. However, it has recently been recognized that ASM cells can also secrete cytokines and chemokines and express cell adhesion molecules that are important for the perpetuation and modulation of airway inflammation. Recent progress has revealed the importance of IgE Fc receptors in stimulating and modulating the function of these cells. In particular, the high-affinity receptor for IgE (FcεRI) has been identified in primary human ASM cells in vitro and in vivo within bronchial biopsies of atopic asthmatic individuals. Moreover, activation of this receptor has been found to induce marked increases in the intracellular calcium concentrations and T helper 2 cytokines and chemokines release. This and other evidence discussed in this review provide an emerging view of FcεR/IgE network as a critical modulator of ASM cell function in allergic asthma.
Src protein tyrosine kinase family and acute inflammatory responses
Authors: Okutani Daisuke , Lodyga Monika , Han Bing , Liu Mingyao
Published: April 2006

Acute inflammatory responses are one of the major underlying mechanisms for tissue damage of multiple diseases, such as ischemia-reperfusion injury, sepsis, and acute lung injury. By use of cellular and molecular approaches and transgenic animals, Src protein tyrosine kinase (PTK) family members have been identified to be essential for the recruitment and activation of monocytes, macrophages, neutrophils, and other immune cells. Src PTKs also play a critical role in the regulation of vascular permeability and inflammatory responses in tissue cells. Importantly, animal studies have demonstrated that small chemical inhibitors for Src PTKs attenuate tissue injury and improve survival from a variety of pathological conditions related to acute inflammatory responses. Further investigation may lead to the clinical application of these inhibitors as drugs for ischemia-reperfusion injury (such as stroke and myocardial infarction), sepsis, acute lung injury, and multiple organ dysfunction syndrome.
Differential regulation of hyaluronan-induced IL-8 and IP-10 in airway epithelial cells
Authors: Boodoo Sada , Spannhake Ernst W. , Powell Jonathan D. , Horton Maureen R.
Published: April 2006

Airway epithelium is emerging as a regulator of local inflammation and immune responses. However, the cellular and molecular mechanisms responsible for the immune modulation by these cells have yet to be fully elucidated. At the cellular level, the hallmarks of airway inflammation are mucus gland hypertrophy with excess mucus production, accumulation of inflammatory mediators, inflammation in the airway walls and lumen, and breakdown and turnover of the extracellular matrix. We demonstrate that fragments of the extracellular matrix component hyaluronan induce inflammatory chemokine production in primary airway epithelial cells grown at an air-liquid interface. Furthermore, hyaluronan fragments use two distinct molecular pathways to induce IL-8 and IFN-γ-inducible protein 10 (IP-10) chemokine expression in airway epithelial cells. Hyaluronan-induced IL-8 requires the MAP kinase pathway, whereas hyaluronan-induced IP-10 utilizes the NF-κB pathway. The induction is specific to low-molecular-weight hyaluronan fragments as other glycosaminoglycans do not induce IL-8 and IP-10 in airway epithelial cells. We hypothesize that not only is the extracellular matrix a target of destruction in airway inflammation but it plays a critical role in perpetuating inflammation through the induction of cytokines, chemokines, and modulatory enzymes in epithelial cells. Furthermore, hyaluronan, by inducing IL-8 and IP-10 by distinct pathways, provides a unique target for differential regulation of key inflammatory chemokines.
Distinct Tumor Stage–Specific Inhibitory Effects of 2-Methoxyestradiol in a Breast Cancer Mouse Model Associated with Id-1 Expression
Authors: Huh Jung-Im , Calvo Alfonso , Charles Rhonda , Green Jeffrey E.
Published: April 2006

2-Methoxyestradiol (2ME2), a metabolite of 17-β-estradiol, inhibits angiogenesis and has additional antitumor activities. We have analyzed the tumor stage–specific effects of 2ME2 in the C3(1)/Tag transgenic mouse model for breast cancer, which spontaneously develops estrogen receptor–negative mammary tumors following a predictable progression of lesion formation. When given either as a therapeutic agent in established tumors (late intervention study) or in mice with pre-invasive mammary lesions (early intervention study), tumor growth was reduced by 60% compared with untreated controls and was associated with an induction of apoptosis. In a prevention study, a significant reduction in mammary intraepithelial neoplasia (MIN) lesions was observed in animals beginning treatment at 6 weeks of age, before the appearance of histopathologic abnormalities. However, although 2ME2 reduced the number of MIN lesions in the prevention study, a paradoxical increase in tumor multiplicity and growth rate was observed. This was associated with unusual cystic tumor formation, in which significant central necrosis was observed, surrounded by an outer region of proliferative tumor cell growth. The characteristics of the cystic tumor formation in mice treated with 2ME2 at early ages are consistent with an impaired angiogenic response as observed in mice deficient for inhibitor of differentiation (Id-1). We further show that Id-1 expression is negatively regulated by 2ME2, which may be an additional mechanism for the antiangiogenic effect of 2ME2. Although 2ME2 significantly reduced tumor growth at late stages, these results also suggest that altered tumor morphology and accelerated tumor growth may occur if 2ME2 is administered in a prevention setting for prolonged periods. (Cancer Res 2006; 66(7): 3495-503)
Two Transforming C-RAF Germ-Line Mutations Identified in Patients with Therapy-Related Acute Myeloid Leukemia
Authors: Zebisch Armin , Staber Philipp B. , Delavar Ali , Bodner Claudia , Hiden Karin , Fischereder Katja , Janakiraman Manickam , Linkesch Werner , Auner Holger W. , Emberger Werner , Windpassinger Christian , Schimek Michael G. , Hoefler Gerald , Troppmair Jakob , Sill Heinz
Published: April 2006

Mutations leading to activation of the RAF-mitogen-activated protein kinase/extracellular signal-regulated (ERK) kinase (MEK)-ERK pathway are key events in the pathogenesis of human malignancies. In a screen of 82 acute myeloid leukemia (AML) samples, 45 (55%) showed activated ERK and thus were further analyzed for mutations in B-RAF and C-RAF. Two C-RAF germ-line mutations, S427G and I448V, were identified in patients with therapy-related AML in the absence of alterations in RAS and FLT3. Both exchanges were located within the kinase domain of C-RAF. In vitro and in vivo kinase assays revealed significantly increased activity for S427GC-RAF but not for I448VC-RAF. The involvement of the S427G C-RAF mutation in constitutive activation of ERK was further confirmed through demonstration of activating phosphorylations on C-RAF, MEK, and ERK in neoplastic cells, but not in nonneoplastic cells. Transformation and survival assays showed oncogenic and antiapoptotic properties for both mutations. Screening healthy individuals revealed a <1/400 frequency of these mutations and, in the case of I448V, inheritance was observed over three generations with another mutation carrier suffering from cancer. Taken together, these data are the first to relate C-RAF mutations to human malignancies. As both mutations are of germ-line origin, they might constitute a novel tumor-predisposing factor. (Cancer Res 2006; 66(7): 3401-8)
Mouse Double Minute 2 Associates with Chromatin in the Presence of p53 and Is Released to Facilitate Activation of Transcription
Authors: White David E. , Talbott Kathryn E. , Arva Nicoleta C. , Bargonetti Jill
Published: April 2006

The tumor suppressor p53 is a potent transcription factor of which the ability to mediate transcription is inhibited through an interaction with the oncoprotein mouse double minute 2 (Mdm2). The present study has tested the hypothesis that Mdm2 inhibits the p53 response in normally growing cells by binding to chromatin-associated p53. Using chromatin immunoprecipitation, we show that Mdm2 localizes with p53 at its responsive elements on the waf1 and mdm2 genes in human cell lines expressing p53, but not in cell lines lacking p53 expression, indicating that Mdm2 is recruited to regions of DNA in a p53-dependent manner. Interestingly, our results show a decrease of Mdm2 protein associated with p53-responsive elements on the waf1 and mdm2 genes when p53-induced transcription is activated either by DNA damage or through controlled overexpression of p53. Rapid activation of p53 transcriptional activity before increasing p53 protein levels was observed with addition of either small-molecule inhibitors to disrupt the p53-Mdm2 interaction or small interfering RNA to mdm2. These findings indicate Mdm2 transiently localizes with p53 at responsive elements and suggest that latent p53 results from the recruitment of Mdm2 to chromatin. (Cancer Res 2006; 66(7): 3463-70)
Growth and Motility Inhibition of Breast Cancer Cells by Epidermal Growth Factor Receptor Degradation Is Correlated with Inactivation of Cdc42
Authors: Hirsch Dianne S. , Shen Yi , Wu Wen Jin
Published: April 2006

Overexpression of epidermal growth factor receptor (EGFR) contributes to increased cell proliferation and migration in breast cancer. However, mechanisms of EGFR overexpression remain elusive and often cannot be attributed to gene amplification. In NIH3T3 fibroblasts, active Cdc42 inhibits c-Cbl-regulated EGFR degradation to induce cellular transformation. Here, we use two EGFR-overexpressing breast cancer cell lines, MDA-MB-231 and BT20, as models to test the hypothesis that up-regulated Cdc42 activity impairs c-Cbl-mediated EGFR degradation and contributes to EGFR overexpression. We show that silencing Cdc42 significantly reduces protein levels of EGFR, leading to a marked reduction in cell proliferation and migration, and c-Cbl knockdown increases the levels of EGFR. Expression of c-Cbl-N480, a c-Cbl mutant that is not regulated by Cdc42 and blocks Cdc42-induced transformation but still binds and ubiquitinates EGFR, enhances the rate of EGFR degradation and subsequently inhibits cell proliferation. Moreover, down-regulated EGFR signaling induced by c-Cbl-N480 decreased activity of Cdc42 and Rac1, resulting in inhibition of cell migration. These findings indicate that Cdc42 and c-Cbl are critical components involved in the regulation of EGFR protein levels and that restoration of proper EGFR degradation by disrupting Cdc42 regulation of c-Cbl can reduce cell proliferation and migration in MDA-MB-231 and BT20 cells. (Cancer Res 2006; 66(7): 3523-30)
N-Methyl-d-Aspartate Receptor Type 2B Is Epigenetically Inactivated and Exhibits Tumor-Suppressive Activity in Human Esophageal Cancer
Authors: Kim Myoung Sook , Yamashita Keishi , Baek Jin Hyen , Park Hannah Lui , Carvalho Andre Lopes , Osada Motonobu , Hoque Mohammad Obaidul , Upadhyay Sunil , Mori Masaki , Moon Chulso , Sidransky David
Published: April 2006

Promoter hypermethylation accompanied by gene silencing is a common feature of human cancers. We identified previously several new tumor suppressor genes based on pharmacologic unmasking of the promoter region and detection of reexpression on microarray analysis. In this study, we modified the selection of candidates from our previous microarray data by excluding genes that showed basal expression in cancer cell lines. With the new method, we found novel methylated genes with 90% accuracy. Among these 33 novel methylated genes that we identified in esophageal squamous cell carcinoma (ESCC) cell lines, N-methyl-d-aspartate receptor type 2B (NMDAR2B) was of particular interest. NMDAR2B was methylated in 95% of primary human ESCC tissue specimens and 12 ESCC cell lines by sequence analysis. NMDAR2B expression was silenced in all 12 ESCC cell lines and was reactivated by the demethylating agent 5-aza-2′-deoxycytidine. Moreover, reintroduction of the gene was accompanied by marked Ca2+-independent apoptosis in ESCC cell lines, suggesting that NMDAR2B can suppress tumor growth. Thus, NMDAR2B promoter methylation is common in ESCC, abrogating gene transcription and leading to cellular resistance to apoptosis. (Cancer Res 2006; 66(7): 3409-18)