bluuebunny/crossref_metadata_2025 huggingface dataset:
DAST CRYSTAL WAVEGUIDE FABRICATION BY PHOTOBLEACHING METHOD
Authors: CAI B. , RADMER O. , ZAWADZKI C. , YAO H. H. , KEIL N. , KAINO T.
Published: July 2004

In order to utilize the large electro-optic coefficient of organic ionic crystal, 4-(4-dimethylaminostyryl)-1-methylpyridinium tosylate (DAST), a photobleaching technique was used for serially grafted DAST crystal waveguide fabrication. To fabricate a low optical loss crystal waveguide, a single-mode serially grafted DAST waveguide model with taper structure has been designed and simulated by beam propagation method (BPM). For the single-mode serially grafted crystal waveguide fabrication, we developed a novel single thin crystal growth method successfully. An attempt for the waveguide fabrication has been carried out. A feasible method for the single-mode crystal waveguide fabrication was proposed.
Biomaterials: Where We Have Been and Where We Are Going
Authors: Ratner Buddy D. , Bryant Stephanie J.
Published: July 2004

▪ Abstract  Since its inception just over a half century ago, the field of biomaterials has seen a consistent growth with a steady introduction of new ideas and productive branches. This review describes where we have been, the state of the art today, and where we might be in 10 or 20 years. Herein, we highlight some of the latest advancements in biomaterials that aim to control biological responses and ultimately heal. This new generation of biomaterials includes surface modification of materials to overcome nonspecific protein adsorption in vivo, precision immobilization of signaling groups on surfaces, development of synthetic materials with controlled properties for drug and cell carriers, biologically inspired materials that mimic natural processes, and design of sophisticated three-dimensional (3-D) architectures to produce well-defined patterns for diagnostics, e.g., biological microelectromechanical systems (bioMEMs), and tissue engineering.
Breast Tissue Engineering
Authors: Patrick Charles W.
Published: July 2004

▪ Abstract  Tissue engineering has the potential to redefine rehabilitation for the breast cancer patient by providing a translatable strategy that restores the postmastectomy breast mound while concomitantly obviating limitations realized with contemporary reconstructive surgery procedures. The engineering design goal is to provide a sufficient volume of viable fat tissue based on a patient's own cells such that deficits in breast volume can be abrogated. To be sure, adipose tissue engineering is in its infancy, but tremendous strides have been made. Numerous studies attest to the feasibility of adipose tissue engineering. The field is now poised to challenge barriers to clinical translation that are germane to most tissue engineering applications, namely scale-up, large animal model development, and vascularization. The innovative and rapid progress of adipose engineering to date, as well as opportunities for its future growth, is presented.
Ocular Biomechanics and Biotransport
Authors: Ethier C. Ross , Johnson Mark , Ruberti Jeff
Published: July 2004

▪ Abstract  The eye transduces light, and we usually do not think of it as a biomechanical structure. Yet it is actually a pressurized, thick-walled shell that has an internal and external musculature, a remarkably complex internal vascular system, dedicated fluid production and drainage tissues, and a variety of specialized fluid and solute transport systems. Biomechanics is particularly involved in accommodation (focusing near and far), as well as in common disorders such as glaucoma, macular degeneration, myopia, and presbyopia. In this review, we give a (necessarily brief) overview of many of the interesting biomechanical aspects of the eye, concluding with a list of open problems.
Micro-Computed Tomography—Current Status and Developments
Authors: Ritman Erik L.
Published: July 2004

▪ Abstract  The recent rapid increase in interest in tomographic imaging of small animals and of human (and large animal) organ biopsies is driven largely by drug discovery, cancer detection/monitoring, phenotype identification and/or characterization, and development of disease detection methods and monitoring efficacies of drugs in disease treatment. In biomedical applications, micro-computed tomography (CT) scanners can function as scaled-down (i.e., mini) clinical CT scanners that provide a three-dimensional (3-D) image of most, if not the entire, torso of a mouse at image resolution (50–100 μm) scaled proportional to that of a human CT image. Micro-CT scanners, on the other hand, image specimens the size of intact rodent organs at spatial resolutions from cellular (20 μm) down to subcellular dimensions (e.g., 1 μm) and fill the resolution-hiatus between microscope imaging, which resolves individual cells in thin sections of tissue, and mini-CT imaging of intact volumes.
Engineering Synthetic Vectors for Improved DNA Delivery: Insights from Intracellular Pathways
Authors: Roth Charles M. , Sundaram Sumati
Published: July 2004

▪ Abstract  Significant progress has been made in the area of nonviral gene delivery to date. Yet, synthetic vectors remain less efficient by orders of magnitude than their viral counterparts. Research continues toward unraveling and overcoming various barriers to the efficient delivery of DNA, whether in plasmid form encoding a gene or as an oligonucleotide for the selective inhibition of target gene expression. Novel components for overcoming these hurdles are continually being incorporated into the design of synthetic vectors, leading to increasingly more virus-like particles. Despite these advances, general principles defining the design of synthetic vectors are yet to be developed fully. A more quantitative analysis of the cellular uptake and intracellular processing of these vectors is required for the rational manipulation of vector design. Mathematical frameworks with a more conceptual basis will help obtain an integrated perspective on these complex systems. In this review, we critically examine the progress made toward the improved design of synthetic vectors by the strategic exploitation of intracellular mechanisms and explore newer possibilities to overcome obstacles in the practical realization of this field.
Robotics, Motor Learning, and Neurologic Recovery
Authors: Reinkensmeyer David J. , Emken Jeremy L. , Cramer Steven C.
Published: July 2004

▪ Abstract  Robotic devices are helping shed light on human motor control in health and injury. By using robots to apply novel force fields to the arm, investigators are gaining insight into how the nervous system models its external dynamic environment. The nervous system builds internal models gradually by experience and uses them in combination with impedance and feedback control strategies. Internal models are robust to environmental and neural noise, generalized across space, implemented in multiple brain regions, and developed in childhood. Robots are also being used to assist in repetitive movement practice following neurologic injury, providing insight into movement recovery. Robots can haptically assess sensorimotor performance, administer training, quantify amount of training, and improve motor recovery. In addition to providing insight into motor control, robotic paradigms may eventually enhance motor learning and rehabilitation beyond the levels possible with conventional training techniques.
Taurine inhibits apoptosis by preventing formation of the Apaf-1/caspase-9 apoptosome
Authors: Takatani Tomoka , Takahashi Kyoko , Uozumi Yoriko , Shikata Eriko , Yamamoto Yasuhiro , Ito Takashi , Matsuda Takahisa , Schaffer Stephen W. , Fujio Yasushi , Azuma Junichi
Published: July 2004

Cardiomyocyte apoptosis contributes to cell death during myocardial infarction. One of the factors that regulate the degree of apoptosis during ischemia is the amino acid taurine. To study the mechanism underlying the beneficial effect of taurine, we examined the interaction between taurine and mitochondria-mediated apoptosis using a simulated ischemia model with cultured rat neonatal cardiomyocytes sealed in closed flasks. Exposure to medium containing 20 mM taurine reduced the degree of apoptosis following periods of ischemia varying from 24 to 72 h. In the untreated group, simulated ischemia for 24 h led to mitochondrial depolarization accompanied by cytochrome c release. The apoptotic cascade was also activated, as evidenced by the activation of caspase-9 and -3. Taurine treatment had no effect on mitochondrial membrane potential and cytochrome c release; however, it inhibited ischemia-induced cleavage of caspase-9 and -3. Taurine loading also suppressed the formation of the Apaf-1/caspase-9 apoptosome and the interaction of caspase-9 with Apaf-1. These findings demonstrate that taurine effectively prevents myocardial ischemia-induced apoptosis by inhibiting the assembly of the Apaf-1/caspase-9 apoptosome.
Evidence for stabilization of aquaporin-2 folding mutants by N-linked glycosylation in endoplasmic reticulum
Authors: Buck Teresa M. , Eledge Joel , Skach William R.
Published: July 2004

Aquaporin-2 (AQP2) is the vasopressin-sensitive water channel that regulates water reabsorption in the distal nephron collecting duct. Inherited AQP2 mutations that disrupt folding lead to nephrogenic diabetes insipidus (NDI) by targeting newly synthesized protein for degradation in the endoplasmic reticulum (ER). During synthesis, a subset of wild-type (WT) AQP2 is covalently modified by N-linked glycosylation at residue Asn123. To investigate the affect of glycosylation, we expressed WT AQP2 and four NDI-related mutants in Xenopus laevis oocytes and compared stability of glycosylated and nonglycosylated isoforms. In all constructs, ∼15–20% of newly synthesized AQP2 was covalently modified by N-linked glycosylation. At steady state, however, core glycosylated WT protein was nearly undetectable, whereas all mutants were found predominantly in the glycosylated form (60–70%). Pulse-chase metabolic labeling studies revealed that glycosylated isoforms of mutant AQP2 were significantly more stable than their nonglycosylated counterparts. For nonglycosylated isoforms, the half-life of WT AQP2 was significantly greater (>48 h) than that of mutant AQP2 (T126M 4.1 ± 1.0 h, A147T 4.2 ± 0.60 h, C181W 4.5 ± 0.50 h, R187C 6.8 ± 1.2 h). This is consistent with rapid turnover in the ER as previously reported. In contrast, the half-lives of mutant proteins containing N-linked glycans were similar to WT (∼25 h), indicating that differences in steady-state glycosylation profiles are caused by increased stability of glycosylated mutant proteins. These results suggest that addition of a single N-linked oligosaccharide moiety can partially compensate for ER folding defects induced by disease-related mutations.
Synaptic transmission in simple motility reflex pathways excited by distension in guinea pig distal colon
Authors: Bian X.-C. , Heffer L. F. , Gwynne R. M. , Bornstein J. C. , Bertrand P. P.
Published: July 2004

We examined specific receptor/transmitter combinations used at functionally identified synapses in ascending and descending reflex pathways of guinea pig distal colon. Excitatory (EJPs) or inhibitory junction potentials (IJPs) were recorded intracellularly from nicardipine-paralyzed circular smooth muscle in either the oral or anal recording chamber of a three-chambered organ bath, respectively. Blockade of synaptic transmission in the central chamber with a 0.25 mM Ca2+/12 mM Mg2+ solution abolished EJPs evoked by distension applied either in the central or the far (anal) chamber. IJPs evoked by distension in the central or the far (oral) chamber were depressed to ∼50% of control. Hexamethonium (nicotinic receptor antagonist, 200 μM) in the central chamber reduced IJPs evoked by far or central distension to 50%, whereas EJPs evoked by far distension were abolished and EJPs evoked by central distension were reduced to 70% of control. Hexamethonium in the recording chambers reduced both IJPs and EJPs evoked by central distension to ∼50%. EJPs in the ascending pathway were unaffected by blockade of muscarinic receptors in the central chamber or blockade of neurokinin 3 tachykinin receptors in this or the recording chamber. In the descending pathway, blockade of P2 receptors in the same chambers had only a minor effect on distension-evoked IJPs. Thus some intrinsic sensory neurons of guinea pig colon have long descending projections (>30 mm), but ascending projections of <15 mm. In contrast to the ileum, transmission between ascending or descending interneurons and from sensory neurons to descending interneurons is predominantly via nicotinic receptors; but transmission to inhibitory or excitatory motoneurons and from sensory neurons to ascending interneurons involves nicotinic and other unidentified receptors.
Tumor necrosis factor-α stimulates gastric epithelial cell proliferation
Authors: Luo Jiing Chyuan , Shin Vivian Yvonne , Yang Ying Hua , Wu William Ka Kei , Ye Yi Ni , So Wallace Hau Leung , Chang Full Young , Cho Chi Hin
Published: July 2004

TNF-α is a cytokine produced during gastric mucosal injury. We examined whether TNF-α could promote mucosal repair by stimulation of epithelial cell proliferation and explored further the underlying mechanisms in a rat gastric mucosal epithelial cell line (RGM-1). TNF-α treatment (1–10 ng/ml) for 12 or 24 h significantly increased cell proliferation but did not induce apoptosis in RGM-1 cells. TNF-α treatment significantly increased cytosolic phospholipase A2 and cyclooxygenase-2 (COX-2) protein expression and PGE2 level but did not affect the protein levels of EGF, basic fibroblast growth factor, and COX-1 in RGM-1 cells. The mRNA of TNF receptor (TNF-R) 2 but not of TNF-R1 was also increased. Dexamethasone dose dependently inhibited the stimulatory effect of TNF-α on cell proliferation, which was associated with a significant decrease in cellular COX-2 expression and PGE2 level. A selective COX-2 inhibitor 3-(3-fluorophenyl)-4-[4-(methylsulfonyl)phenyl]-5,5-dimethyl-5H-furan-2-one (DFU) by itself had no effect on basal cell proliferation but significantly reduced the stimulatory effect of TNF-α on RMG-1 cells. Combination of dexamethasone and DFU did not produce an additive effect. PGE2 significantly reversed the depressive action of dexamethasone on cell proliferation. These results suggest that TNF-α plays a regulatory role in epithelial cell repair in the gastric mucosa via the TNF-α receptor and activation of the arachidonic acid/PG pathway.
Obese and diabetic db/db mice develop marked liver fibrosis in a model of nonalcoholic steatohepatitis: role of short-form leptin receptors and osteopontin
Authors: Sahai Atul , Malladi Padmini , Pan Xiaomin , Paul Rachelle , Melin-Aldana Hector , Green Richard M. , Whitington Peter F.
Published: July 2004

Obesity and type 2 diabetes are associated with nonalcoholic steatohepatitis (NASH), but an obese/diabetic animal model that mimics human NASH remains undefined. We examined the induction of steatohepatitis and liver fibrosis in obese and type 2 diabetic db/ db mice in a nutritional model of NASH and determined the relationship of the expressions of osteopontin (OPN) and leptin receptors to the pathogenesis of NASH. db/ db mice and the corresponding lean and nondiabetic db/ m mice were fed a diet deficient in methionine and choline (MCD diet) or control diet for 4 wk. Leptin-deficient obese and diabetic ob/ ob mice fed similar diets were used for comparison. MCD diet-fed db/ db mice exhibited significantly greater histological inflammation and higher serum alanine aminotransferase levels than db/ m and ob/ ob mice. Trichrome staining showed marked pericellular fibrosis in MCD diet-fed db/ db mice but no significant fibrosis in db/ m or ob/ ob mice. Collagen I mRNA expression was increased 10-fold in db/ db mice, 4-fold in db/ m mice, and was unchanged in ob/ ob mice. mRNA expressions of OPN, TNF-α, TGF-β, and short-form leptin receptors (Ob-Ra) were significantly increased in db/ db mice compared with db/ m or ob/ ob mice. Parallel increases in OPN and Ob-Ra protein levels were observed in db/ db mice. Cultured hepatocytes expressed only Ob-Ra, and leptin stimulated OPN mRNA and protein expression in these cells. In conclusion, our results demonstrate the development of an obese/diabetic experimental model for NASH in db/ db mice and suggest an important role for Ob-Ra and OPN in the pathogenesis of NASH.
Skeletal muscle atrophy is associated with an increased expression of myostatin and impaired satellite cell function in the portacaval anastamosis rat
Authors: Dasarathy Srinivasan , Dodig Milan , Muc Sean M. , Kalhan Satish C. , McCullough Arthur J.
Published: July 2004

Proliferation and differentiation of satellite cells are critical in the regeneration of atrophied muscle following immobilization and aging. We hypothesized that impaired satellite cell function is responsible for the atrophy of skeletal muscle also seen in cirrhosis. Myostatin and insulin-like growth factor 1 (IGF1) have been identified to be positive and negative regulators, respectively, of satellite cell function. Using a rat model of cirrhosis [portacaval anastamosis (PCA)] and sham-operated controls, we examined the expression of myostatin, its receptor activinR2b, and its downstream messenger cyclin-dependant kinase inhibitor p21 (CDKI p21) as well as IGF1 and its receptor in the gastrocnemius muscle. Expression of PCNA, a marker of proliferation, and myogenic regulatory factors (myoD, myf5, and myogenin), markers of differentiation of satellite cells, were also measured. Real- time PCR for mRNA and Western blot assay for protein quantification were performed. PCA rats had lower body weight and gastrocnemius weight compared with sham animals ( P < 0.05). PCNA and myogenic regulatory factors were lower in PCA rats ( P < 0.05). Myostatin, activinR2b, and CDKI p21 were higher in the PCA animals ( P < 0.05). The expression of IGF1 and its receptor was lower in liver and skeletal muscle of PCA animals ( P < 0.05). These data suggest that skeletal muscle atrophy seen in the portacaval shunted rats is a consequence of impaired satellite cell proliferation and differentiation mediated, in part, by higher myostatin and lower IGF1 expression.
Sera from patients with idiopathic dilated cardiomyopathy decrease ICa in cardiomyocytes isolated from rabbits
Authors: del Corsso Cristiane , de Carvalho Antônio Carlos Campos , Martino Helena Furtado , Varanda Wamberto Antonio
Published: July 2004

Autoantibodies against muscarinic and adrenergic receptors have been found in the sera of patients with idiopathic dilated cardiomyopathy (IDC) and Chagas disease, but it is still unclear whether they can functionally interact with their respective receptors to modulate cardiac functions. In this study, our goal was to detect the presence of those antibodies in the sera of patients with IDC and characterize their electrophysiological effects on cardiomyocytes from rabbits. By using ELISA immunoassays, we detected high titers of antibodies against muscarinic M2 receptors in the sera of all IDC patients, whereas the detection of antibodies against the β1-receptor occurred in 50% of them. Electrophysiological experiments using the whole cell configuration of the patch-clamp technique showed that sera from 43% of IDC patients induced a significant decrease (∼26%) in isoproterenol-stimulated L-type Ca2+ currents in rabbit ventricular myocytes, whereas the sera from healthy blood donors failed to do so. As expected, IDC sera also decreased the action potential duration (by 10.5%) due to a shortening of the plateau phase. Sera that reduced isoproterenol-stimulated L-type Ca2+ currents did not cause any effect on K+ currents. We conclude that sera from IDC patients have autoantibodies, which interact with muscarinic M2 receptors of rabbit cardiomyocytes, acting in an agonist-like fashion. This action results in changes in electrogenesis, which, as often observed in patients with IDC, could initiate ventricular arrhythmias that lead to sudden death.
Continuous peripheral resistance measurement during hemorrhagic hypotension
Authors: Torres Luciana N. , Torres Filho Ivo P. , Barbee R. Wayne , Tiba M. Hakam , Ward Kevin R. , Pittman Roland N.
Published: July 2004

We tested the hypotheses that continuous total peripheral resistance (TPR) measurements are superior to intermittent data collection and that variables related to TPR can be used to distinguish between survivors and nonsurvivors (NS), respectively, of prolonged hemorrhagic hypotension (HH). One week after a transit-time ultrasound probe was implanted on their ascending aortas, 21 rats were subjected to 4 h of HH at 40 mmHg. Measurements were made before and up to 4 h after initiation of HH. Additional bleeding or Ringer l-lactate (RL) infusion was used to maintain HH. TPR was continuously measured online using recordings of blood flow and arterial pressure. Approximately 67% of the rats survived ≥3 h; others were considered NS. Data collected at 30-min intervals failed to detect the maximum value of TPR (TPRmax). The times to reach TPRmax were similar for survivors and NS and were strongly correlated with the bleeding end points and with the RL infusion-onset times. However, survivors showed higher TPRmax values than NS ( P < 0.005) and had a significantly longer period than NS during which TPR was above baseline level (116 ± 20 vs. 51 ± 10 min). In conclusion, 1) the transit-time ultrasound technique at high sampling rate allowed continuous and accurate real-time monitoring of TPR, 2) the bleeding end point and RL infusion-onset times may be used as surrogates of the time to TPRmax, 3) TPRmax of survivors and NS could be detected only using a continuous TPR measurement, and 4) differences between survivors and NS could be revealed by the continuous TPR curve.
Selective decontamination of the digestive tract attenuated the myocardial inflammation and dysfunction that occur with burn injury
Authors: Horton Jureta W. , Tan Jing , White D. Jean , Maass David L. , Thomas James A.
Published: July 2004

This study examined the effects of oral antibiotics to selectively decontaminate the digestive tract (SDD) on postburn myocardial signaling, inflammation, and function. We hypothesized that antibiotic therapy to eliminate pathogens from the gastrointestinal (GI) tract would reduce myocardial inflammatory responses and improve postburn myocardial performance. Sprague-Dawley rats received polymyxin E (15 mg), tobramycin (6 mg), and 5-flucytosin (100 mg) by oral gavage twice daily for 3 days preburn and 24 h postburn. Experimental groups included 1) sham burn given vehicle (3 ml water), 2) sham plus SDD, 3) burn over 40% total body surface area (TBSA) plus SDD, and 4) burn over 40% TBSA given vehicle. All burns received lactated Ringer solution (4 mg·kg−1·%burn−1); myocardial signaling (PKCε/p38 MAPK/NF-κB) was studied 2, 4, and 24 h postburn; and cytokine secretion (systemic and myocyte secreted cytokines, ELISA) and cardiac function were examined 24 h postburn. Vehicle-treated burn injury increased myocardial PKCε/p38 MAPK expression, promoted NF-κB nuclear translocation, promoted TNF-α, IL-1β, IL-6, and IL-10 secretion, and impaired myocardial function. SDD attenuated burn-related proinflammatory myocardial signaling, cytokine secretion, and myocardial contractile defects. Our data suggest that burn-related loss of GI barrier function and translocation of microbial products serve as upstream mediators of postburn myocardial inflammatory signaling and dysfunction.
Loss of atrial contractility is primary cause of atrial dilatation during first days of atrial fibrillation
Authors: Schotten Ulrich , de Haan Sunniva , Neuberger Hans-Ruprecht , Eijsbouts Sabine , Blaauw Yuri , Tieleman Robert , Allessie Maurits
Published: July 2004

Atrial fibrillation (AF) induces a progressive dilatation of the atria which in turn might promote the arrhythmia. The mechanism of atrial dilatation during AF is not known. To test the hypothesis that loss of atrial contractile function is a primary cause of atrial dilatation during the first days of AF, eight goats were chronically instrumented with epicardial electrodes, a pressure transducer in the right atrium, and piezoelectric crystals to measure right atrial diameter. AF was induced with the use of repetitive burst pacing. Atrial contractility was assessed during sinus rhythm, atrial pacing (160-, 300-, and 400-ms cycle length), and electrically induced AF. The compliance of the fibrillating right atrium was measured during unloading the atria with diuretics and loading with 1 liter of saline. All measurements were repeated after 6, 12, and 24 h of AF and then once a day during the first 5 days of AF. Recovery of the observed changes after spontaneous cardioversion was also studied. After 5 days of AF, atrial contractility during sinus rhythm or slow atrial pacing was greatly reduced. During rapid pacing (160 ms) or AF, the amplitude of the atrial pressure waves had declined to 20% of control. The compliance of the fibrillating atria increased twofold, whereas the right atrial pressure was unchanged. As a result, the mean right atrial diameter increased by ∼12%. All changes were reversible within 3 days of sinus rhythm. We conclude that atrial dilatation during the first days of AF is due to an increase in atrial compliance caused by loss of atrial contractility during AF. Atrial compliance and size are restored when atrial contractility recovers after cardioversion of AF.
N-acetyl-seryl-aspartyl-lysyl-proline stimulates angiogenesis in vitro and in vivo
Authors: Wang Dahai , Carretero Oscar A. , Yang Xiao-Yi , Rhaleb Nour-Eddine , Liu Yun-He , Liao Tang-Dong , Yang Xiao-Ping
Published: July 2004

N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), a natural inhibitor of pluripotent hematopoietic stem cell proliferation, has been suggested as capable of promoting an angiogenic response. We studied whether Ac-SDKP stimulates endothelial cell proliferation, migration, and tube formation; enhances angiogenic response in the rat cornea after implantation of a tumor spheroid; and increases capillary density in rat hearts with myocardial infarction (MI). In vitro, an immortal BALB/c mouse aortic endothelial 22106 cell line was used to determine the effects of Ac-SDKP on endothelial cell proliferation and migration and tube formation. In vivo, a 9L-gliosarcoma cell spheroid (250–300 μm in diameter) was implanted in the rat cornea and vehicle or Ac-SDKP (800 μg·kg−1·day−1ip) infused via osmotic minipump. Myocardial capillary density was studied in rats with MI given either vehicle or Ac-SDKP. We found that Ac-SDKP 1) stimulated endothelial cell proliferation and migration and tube formation in a dose-dependent manner, 2) enhanced corneal neovascularization, and 3) increased myocardial capillary density. Endothelial cell proliferation and angiogenesis stimulated by Ac-SDKP could be beneficial in cardiovascular diseases such as hypertension and MI. Furthermore, because Ac-SDKP is mainly cleaved by ACE, it may partially mediate the cardioprotective effect of ACE inhibitors.
Effect of glycocalyx on shear-dependent albumin uptake in endothelial cells
Authors: Ueda Akinori , Shimomura Manabu , Ikeda Mariko , Yamaguchi Ryuhei , Tanishita Kazuo
Published: July 2004

The glycocalyx layer on the surface of an endothelial cell is an interface barrier for uptake of macromolecules, such as low-density lipoprotein and albumin, in the cell. The shear-dependent uptake of macromolecules thus might govern the function of the glycocalyx layer. We therefore studied the effect of glycocalyx on the shear-dependent uptake of macromolecules into endothelial cells. Bovine aorta endothelial cells were exposed to shear stress stimulus ranging from 0.5 to 3.0 Pa for 48 h. The albumin uptake into the cells was then measured using confocal laser scanning microscopy, and the microstructure of glycocalyx was observed using electron microscopy. Compared with the uptake into endothelial cells under static conditions (no shear stress stimulus), the albumin uptake at a shear stress of 1.0 Pa increased by 16% and at 3.0 Pa decreased by 27%. Compared with static conditions, the thickness of the glycocalyx layer increased by 70% and the glycocalyx charge increased by 80% at a shear stress of 3.0 Pa. The albumin uptake at a shear stress of 3.0 Pa for cells with a neutralized (no charge) glycocalyx layer was almost twice that of cells with charged layer. These findings indicate that glycocalyx influences the albumin uptake at higher shear stress and that glycocalyx properties (thickness and charge level) are involved with the shear-dependent albumin uptake process.
Hemodynamic and sympathoadrenal responses to mental stress during nitric oxide synthesis inhibition
Authors: Lindqvist Madeleine , Melcher Anders , Hjemdahl Paul
Published: July 2004

Cardiovascular and sympathoadrenal responses to a reproducible mental stress test were investigated in eight healthy young men before and during intravenous infusion of the nitric oxide (NO) synthesis inhibitor N-monomethyl-l-arginine (l-NMMA). Before l-NMMA, stress responses included significant increases in heart rate, mean arterial pressure, and cardiac output (CO) and decreases in systemic and forearm vascular resistance. Arterial plasma norepinephrine (NE) increased. At rest after 30 min of infusion of l-NMMA (0.3 mg·kg−1·min−1 iv), mean arterial pressure increased from 98 ± 4 to 108 ± 3 mmHg ( P < 0.001) because of an increase in systemic vascular resistance from 12.9 ± 0.5 to 18.5 ± 0.9 units ( P < 0.001). CO decreased from 7.7 ± 0.4 to 5.9 ± 0.3 l/min ( P < 0.01). Arterial plasma NE decreased from 2.08 ± 0.16 to 1.47 ± 0.14 nmol/l. Repeated mental stress during continued infusion of l-NMMA (0.15 mg·kg−1·min−1) induced qualitatively similar cardiovascular responses, but there was a marked attenuation of the increase in mean arterial blood pressure, resulting in similar “steady-state” blood pressures during mental stress without and with NO blockade. Increases in heart rate and CO were attenuated, but stress-induced decreases in systemic and forearm vascular resistance were essentially unchanged. Arterial plasma NE increased less than during the first stress test. Thus the increased arterial tone at rest during l-NMMA infusion is compensated for by attenuated increases in blood pressure during mental stress, mainly through a markedly attenuated CO response and suppressed sympathetic nerve activity.
The gastrointestinal tract “tastes” nutrients: evidence from the intestinal taste aversion paradigm
Authors: Tracy Andrea L. , Phillips Robert J. , Chi Michael M. , Powley Terry L. , Davidson T. L.
Published: July 2004

To develop and use a behavioral paradigm for assessments of what nutrient properties are detected by intestinal chemoreceptors, we combined features of the “electronic esophagus” preparation (Elizalde G and Sclafani A. Physiol Behav 47: 63–77, 1990) and the conditioned taste aversion protocol (Garcia J and Koelling RA. Psychon Sci 4: 123–124, 1966). In four experiments, separate groups of food-deprived rats with gastric ( experiments 1–4) or duodenal ( experiment 4) catheters were infused with either carbohydrates (maltodextrin) or fats (corn oil) into their stomachs or small intestines, either while they consumed nonnutritive flavored solutions ( experiments 1 and 2) or in the absence of any intake ( experiments 3 and 4). For some animals, one of the macronutrient infusions was paired with lithium chloride injections shown to support conventional conditioned aversions. After training, in various oral preference test trials, animals were given opportunities to taste and consume the nonnutritive solutions that had served as oropharyngeal conditioned stimuli as well as the nutrients that had been infused intragastrically, with or without poisoning, but never sampled by mouth. As previously established, preferences for the nonnutritive flavors were enhanced by association with intragastric infusions of macronutrients, with carbohydrates producing the greater preference. On first exposure to the two macronutrients for oral consumption, animals reduced their intake of the nutrient that had been previously poisoned when it was infused into the gastrointestinal tract. These results, along with additional controls, suggest that nutrient tastes detected in the intestines can be recognized centrally based on oropharyngeal gustatory stimulation.
Osmoregulation of atrial myocytic ANP release: osmotransduction via cross-talk between L-type Ca2+channel and SR Ca2+release
Authors: Jin Jing Yu , Wen Jin Fu , Li Dan , Cho Kyung Woo
Published: July 2004

Hyperosmolality has been known to increase ANP release. However, its physiological role in the regulation of atrial myocytic ANP release and the mechanism by which hyperosmolality increases ANP release are to be defined. The purpose of the present study was to define these questions. Experiments were performed in perfused beating rabbit atria. Hyperosmolality increased atrial ANP release, cAMP efflux, and atrial dynamics in a concentration-dependent manner. The osmolality threshold for the increase in ANP release was as low as 10 mosmol/kgH2O (∼3%) above the basal levels (1.55 ± 1.71, 17.19 ± 3.11, 23.15 ± 5.49, 54.04 ± 11.98, and 62.00 ± 13.48% for 10, 20, 30, 60, and 100 mM mannitol, respectively; all P < 0.01). Blockade of sarcolemmal L-type Ca2+channel activity, which increased ANP release, attenuated hyperosmolality-induced increases in ANP release (−13.58 ± 4.68% vs. 62.00 ± 13.48%, P < 0.001) and cAMP efflux but not atrial dynamics. Blockade of the Ca2+release from the sarcoplasmic reticulum, which increased ANP release, attenuated hyperosmolality-induced increases in ANP release (13.44 ± 7.47% vs. 62.00 ± 13.48%, P < 0.01) and dynamics but not cAMP efflux. Blockades of Na+-K+-2Cl−cotransporter, Na+/H+exchanger, and Na+/Ca2+exchanger had no effect on hyperosmolality-induced increase in ANP release. The present study suggests that hyperosmolality regulates atrial myocytic ANP release and that the mechanism by which hyperosmolality activates ANP release is closely related to the cross-talk between the sarcolemmal L-type Ca2+channel activity and sarcoplasmic reticulum Ca2+release, possibly inactivation of the L-type Ca2+channels.
Hemoglobin levels in Qinghai-Tibet: different effects of gender for Tibetans vs. Han
Authors: Wu Tianyi , Wang Xiaoqin , Wei Chunyin , Cheng Huawei , Wang Xiaozhen , Li Yan , Ge-Dong  , Zhao Haining , Young Ping , Li Guilan , Wang Zhigang
Published: July 2004

The Tibetan population, long a resident on the Qinghai-Tibetan Plateau, has lower hemoglobin concentrations than Han Chinese migrants, but it is incompletely known how gender affects the hemoglobin concentrations in the two populations at various altitudes. Measurements of hemoglobin concentration were obtained in 5,887 healthy male and female Tibetan and Han residents aged 5–60 yr, at altitudes of 2,664, 3,813, 4,525, and 5,200 m. Multiple regression equations showed the β-coefficients for altitude and for age were higher ( P < 0.05) in Han men than in Tibetan men and in Han women than in Tibetan women. Analysis indicated a significant three-way interaction between altitude, gender, and ethnicity (χ2 = 3.72, P = 0.05). With increasing altitude, men progressively had more hemoglobin than women in the Han, but not the Tibetan, population. Above 2,664 m, this gender-related difference in hemoglobin concentration increased from childhood to young adulthood more in Han than in Tibetans. We suggest that the Han-Tibetan ethnic difference in the effect of altitude on hemoglobin concentration depends to a large extent on gender.
Effect of Subthreshold Up and Down States on the Whisker-Evoked Response in Somatosensory Cortex
Authors: Sachdev Robert N. S. , Ebner Ford F. , Wilson Charles J.
Published: July 2004

Changes in spontaneous activity within the cortex recognized by subthreshold fluctuations of the membrane potential of cortical neurons modified the response of cortical neurons to sensory stimuli. Sensory stimuli occurring in the hyperpolarized “down” state evoked a larger depolarization and were more effective in evoking action potentials than stimuli occurring in the depolarized “up” state. Direct electrical stimulation of the thalamus showed the same dependence on the cell's state at the time of the stimulus, ruling out a strictly thalamic mechanism. Stimuli were more effective at triggering action potentials in the down state even during moderate de- or hyperpolarization of the somatic membrane potential. The postsynaptic potential (PSP) evoked from the down state was larger than the up state PSP but achieved about the same peak membrane potential, which was also near the reversal potential of the PSP (about –51 mV). Chloride loading shifted the reversal potentials of both the up state and the whisker-evoked PSP toward a more depolarized membrane potential. In addition, the threshold for action potentials evoked from the down state was lower than for spikes evoked in the up state. Thus the larger PSP from the down state may be caused by its larger driving force, and the state dependence of action potential generation in response to whisker stimulation may in part be related to a shift in threshold. Different mechanisms are therefore responsible for the state-dependence of PSP amplitude and the spike frequency response to the whisker stimulus.
Genetics of Ultrasonographic Carotid Atherosclerosis
Authors: Manolio Teri A. , Boerwinkle Eric , O’Donnell Christopher J. , Wilson Alexander F.
Published: July 2004

The search for genes related to the cause of common complex disorders such as cardiovascular disease has been frustrating, partly because of the many factors known to contribute to cardiovascular disease and the potential “distance” of cardiovascular disease as a phenotype from genes and gene products. Linkage and association studies for phenotypes more proximal in the pathway from DNA sequence variation to overt clinical disease, such as ultrasound-defined carotid atherosclerosis, may potentially be more enlightening. Only one genetic variant previously reported to be associated with atherosclerosis or clinically evident cardiovascular disease, matrix metalloproteinase (MMP) 3, has shown consistently positive associations with carotid disease, although it has not been studied widely. Another, PON1 L55M, is weakly associated in subgroups only, and 2, ApoE and MTHFR, are equivocal. Genetic variants reported to be associated with clinical cardiovascular disease show weak or no relationship to carotid atherosclerosis. This may reflect the known inconsistency in associations of genetic variants with clinical cardiovascular disease itself. Alternatively, genetic determinants of ultrasound-defined carotid atherosclerosis may differ from those of clinically manifest cardiovascular disease and may require pursuit through large-scale genomic studies of carotid atherosclerosis as a distinct phenotype.
B-Myb Represses Vascular Smooth Muscle Cell Collagen Gene Expression and Inhibits Neointima Formation After Arterial Injury
Authors: Hofmann Claudia S. , Sullivan Christopher P. , Jiang Hao-Yuan , Stone Phillip J. , Toselli Paul , Reis Ernane D. , Chereshnev Igor , Schreiber Barbara M. , Sonenshein Gail E.
Published: July 2004

Objectives—

The function of B-Myb, a negative regulator of vascular smooth muscle cell (SMC) matrix gene transcription, was analyzed in the vasculature.

Methods and Results—

Mice were generated in which the human B
-myb
gene was driven by the basal cytomegalovirus promoter, and 3 founders were identified. Mice appeared to develop normally, and human B-
myb
was expressed in the aortas. Total B-Myb levels were elevated in aortas of adult transgenic versus wild-type (WT) animals and varied inversely with α1(I) collagen mRNA expression. However, neonatal WT and transgenic aortas displayed comparable levels of α1(I) collagen mRNA, likely resulting from elevated levels of cyclin A, which ablated repression by B-Myb. Aortic SMCs from adult transgenic animals displayed decreased α1(I) collagen mRNA levels. To examine the role of B-Myb after vascular injury, animals were subjected to femoral artery denudation, which induces SMC-rich lesion formation. A dramatic reduction in neointima formation and lumenal narrowing was observed in arteries of B-
myb
transgenic versus WT mice 4 weeks after injury.

Conclusions—

Data indicate that B-Myb, which inhibits matrix gene expression in the adult vessel wall, reduces neointima formation after vascular injury.
Systemic Regulation of Vascular NAD(P)H Oxidase Activity and Nox Isoform Expression in Human Arteries and Veins
Authors: Guzik Tomasz J. , Sadowski Jerzy , Kapelak Boguslaw , Jopek Andrzej , Rudzinski Pawel , Pillai Ravi , Korbut Richard , Channon Keith M.
Published: July 2004

Objective—

Impaired endothelial function, characterized by nitric oxide scavenging by increased superoxide production, is a hallmark of vascular disease states. However, molecular mechanisms regulating superoxide production in human blood vessels remain poorly defined.

Methods and Results—

We compared endothelial function, vascular superoxide production, and the expression of NAD(P)H oxidase subunits in arteries and veins from patients undergoing coronary bypass surgery (n=86). Superoxide release was similar in arteries and veins. Inhibitor studies revealed that the NAD(P)H oxidase system was a quantitatively and proportionately greater source of superoxide in veins, whereas xanthine oxidase also contributed significantly to superoxide production in arteries. Moreover, NAD(P)H oxidase molecular composition differed in veins and arteries; veins expressed more nox2 and p22phox, whereas the relative expression of nox4 was greater in arteries. However, there were strong correlations between p22phox and nox4 expression and between superoxide production, NAD(P)H oxidase activity, and endothelial function in arteries and veins from the same patient.

Conclusions—

In individuals with coronary artery disease, changes in vascular superoxide production, endothelial function, and NAD(P)H oxidase activity and expression are related in veins and arteries. These findings highlight the importance of systemic effects on the molecular regulation of the NAD(P)H oxidases in human vascular disease.
L-type Voltage-Gated Ca
2+
Channels Modulate Expression of Smooth Muscle Differentiation Marker Genes via a Rho Kinase/Myocardin/SRF–Dependent Mechanism
Authors: Wamhoff B.R. , Bowles D.K. , McDonald O.G. , Sinha S. , Somlyo A.P. , Somlyo A.V. , Owens G.K.
Published: July 2004

Vascular smooth muscle cell (SMC) contraction is mediated in part by calcium influx through L-type voltage-gated Ca
2+
channels (VGCC) and activation of the RhoA/Rho kinase (ROK) signaling cascade. We tested the hypothesis that Ca
2+
influx through VGCCs regulates SMC differentiation marker expression and that these effects are dependent on RhoA/ROK signaling. Depolarization-induced activation of VGCCs resulted in a nifedipine-sensitive increase in endogenous smooth muscle myosin heavy chain (SMMHC) and SM α-actin expression and CArG-dependent promoter activity, as well as c-fos promoter activity. The ROK inhibitor, Y-27632, prevented depolarization-induced increase in SMMHC/SM α-actin but had no effect on c-fos expression. Conversely, the Ca
2+
/calmodulin-dependent kinase inhibitor, KN93, prevented depolarization-induced increases in c-fos expression with no effect on SMMHC/SM α-actin. Depolarization increased expression of myocardin, a coactivator of SRF that mediates CArG-dependent transcription of SMC marker gene promoters containing paired CArG
cis
regulatory elements (SMMHC/SM α-actin). Both nifedipine and Y-27632 prevented the depolarization-induced increase in myocardin expression. Moreover, short interfering RNA (siRNA) specific for myocardin attenuated depolarization-induced SMMHC/SM α-actin transcription. Chromatin immunoprecipitation (ChIP) assays revealed that depolarization increased SRF enrichment of the CArG regions in the SMMHC, SM α-actin, and c-fos promoters in intact chromatin. Whereas Y-27632 decreased basal and depolarization-induced SRF enrichment in the SMMHC/SM α-actin promoter regions, it had no effect of SRF enrichment of c-fos. Taken together, these results provide evidence for a novel mechanism whereby Ca
2+
influx via VGCCs stimulates expression of SMC differentiation marker genes through mechanisms that are dependent on ROK, myocardin, and increased binding of SRF to CArG
cis
regulatory elements.
Actin Cytoskeleton Organization and Posttranscriptional Regulation of Endothelial Nitric Oxide Synthase During Cell Growth
Authors: Searles Charles D. , Ide Lucienne , Davis Michael E. , Cai Hua , Weber Martina
Published: July 2004

Posttranscriptional regulation of endothelial nitric oxide synthase (eNOS) expression is an important mechanism by which endothelial cells respond to various physiological and pathophysiological stimuli. Previously, we showed that eNOS expression was dramatically altered by the state of cell growth and that the mechanism responsible for this regulation was entirely posttranscriptional, occurring via changes in eNOS mRNA stability. The present study identifies a role for actin cytoskeleton organization in the posttranscriptional regulation of eNOS during cell growth and examines the relationship between the state of actin polymerization and eNOS expression. We identified monomeric actin (globular [G]-actin) as the major component of a 51-kDa ribonucleoprotein that binds to the eNOS mRNA 3′ untranslated region in UV-crosslinking analysis. Binding activity of the ribonucleoprotein complex correlated with the relative concentration of G-actin versus filamentous actin (F-actin). ENOS transcripts colocalized with cytoplasmic G-actin in cells subjected to fluorescence in situ hybridization and G-actin fluorescence staining. In subcellular fractionation studies, eNOS transcripts were enriched in the free polysomal fraction of nonproliferating cells and enriched in the cell matrix-associated polysomal fraction of proliferating cells. Furthermore, an inverse relationship between the concentration of G-actin and eNOS expression was observed in endothelial cells subjected to pharmacological alteration of their cytoskeleton; lower G/F-actin ratios correlated with increased eNOS expression. Our findings provide some insight into how endothelial cells may use the dynamic organization of the actin cytoskeleton to regulate expression of an enzyme that is crucial to vascular homeostasis.
Apoptotic and Necrotic Death Mechanisms Are Concomitantly Activated in the Same Cell After Cerebral Ischemia
Authors: Ünal-Çevik Isın , Kılınç Munire , Can Alp , Gürsoy-Özdemir Yasemin , Dalkara Turgay
Published: July 2004

Background and Purpose—

Both necrotic and apoptotic cell death mechanisms are activated after cerebral ischemia. However, whether they are concomitantly active in the same cell or in discrete cell populations is not known.

Methods—

We investigated activation of both pathways at the cellular level in mice brains subjected to transient or permanent focal ischemia.

Results—

Four hours after ischemia, diffuse cathepsin-B spillage into cytoplasm, suggesting lysosomal leakage, was observed within neurons immunoreactive for the active form of caspase-3 (p20). Ischemic neurons with a leaky plasma membrane (positive for propidium iodide) were colabeled with caspase-cleaved actin fragment and exhibited TUNEL-positive nuclei having apoptotic morphology. At 72 hours, up to 27% of cells with caspase activity displayed morphological features suggestive of secondary necrosis.

Conclusions—

These data, demonstrating an early and concurrent increase in caspase-3 and cathepsin-B activities followed by appearance of caspase-cleavage products, DNA fragmentation, and membrane disintegration, suggest that subroutines of necrotic and apoptotic cell death are concomitantly activated in ischemic neurons and that the dominant cell death phenotype is determined by the relative speed of each process.