bluuebunny/crossref_metadata_2025 huggingface dataset:
Citywide and Local Strategic Partnerships in Urban Regeneration: Can Collaboration Take Things Forward?
Authors: Apostolakis Christos
Published: April 2004

This article explores the issues around the role of collaboration as an essential mechanism in developing strategies for Citywide and Local Strategic partnerships. This is examined in the context of urban regeneration flowing from policy initiatives that have been introduced over recent years. The article sets the scene for collaboration and its characteristics emphasising the attributes of collaborative advantage. Focusing on the latter it then identifies the impact of collaboration on specific strategy areas. Following this the article examines the applicability of collaboration through a case study of a Citywide partnership superseded by a Local Strategic partnership in Leicester. It argues that there is significant evidence of the impact of collaboration on the selected areas of the particular partnership working, although recognising that significant dysfunctional elements exist at the operational and implementation level.
Nationalism or Nationalist Foreign Policy? Contemporary Chinese Nationalism and its Role in Shaping Chinese Foreign Policy in Response to the Belgrade Embassy Bombing
Authors: Shen Simon
Published: April 2004

Focusing on the Chinese response towards the Belgrade Embassy Bombing in 1999 as a case study, this article will address the role of contemporary Chinese nationalism in the Chinese foreign policymaking process. By dividing the meaning of Chinese nationalism into several layers, the author will explore the potential of nationalism in replacing communism as the new frame for Chinese foreign policy after the death of Mao. Then the article will examine four possible explanations in an attempt to account for a primarily nationalist Chinese foreign policy in response to the Belgrade Embassy bombing. Underlying the analysis of these arguments is the suggestion that contemporary Chinese nationalism exists more vividly in official rhetoric than actuality, and that it is unlikely to become the new Chinese foreign policy framer in the future.
What are effective strategies to support pupils with emotional and behavioural difficulties (EBD) in mainstream primary schools? Findings from a systematic review of research
Authors: Evans Jennifer , Harden Angela , Thomas James
Published: April 2004

This article describes the processes and findings of a systematic review of research into the effectiveness of strategies to support pupils with emotional and behavioural difficulties (EBD) in mainstream primary schools. A search for studies carried out from 1975–1999 resulted in 265 citations, of which 96 were found to be within the scope of the review topic. Of these, 27 reported on 28 research studies, which could address the review question. Findings from these 28 studies indicated that a number of strategies, based on a range of theoretical frameworks, showed some positive impacts on pupil behaviour. However, the review highlighted a dearth of good quality research on strategy effectiveness. There is a need for higher quality research into strategies currently being used in schools. Practitioners, parents and children should all be involved in setting the parameters for interventions and research concerned with EBD.
Controversial practices in the education of students with high support needs
Authors: Stephenson Jennifer
Published: April 2004

The use of controversial practices unsupported by research is a concern in special education, especially for students with high support needs. Internet sites of Australian schools enrolling students with moderate to severe intellectual disability (moderate to severe learning difficulties) were located and reviewed to determine the kinds of controversial practices employed and the number of schools reporting their use. Almost half the sample reported utilising at least one unsupported practice and in general there were few convincing rationales provided for the adoption of these practices. The use of unsupported practices in schools may be related to the inaccessibility of research, teacher mistrust of research, teacher reliance on more informal and personal sources of information, and teacher desire to achieve results and build positive relationships. More research is needed to understand why these practices are adopted and the ways in which they are used.
Are there Characteristics of Infectious Diseases that Raise Special Ethical Issues?1
Authors: Smith Charles B. , Battin Margaret P. , Jacobson Jay A. , Francis Leslie P. , Botkin Jeffrey R. , Asplund Emily P. , Domek Gretchen J. , Hawkins Beverly
Published: April 2004

This paper examines the characteristics of infectious diseases that raise special medical and social ethical issues, and explores ways of integrating both current bioethical and classical public health ethics concerns. Many of the ethical issues raised by infectious diseases are related to these diseases’ powerful ability to engender fear in individuals and panic in populations. We address the association of some infectious diseases with high morbidity and mortality rates, the sense that infectious diseases are caused by invasion or attack on humans by foreign micro‐organisms, the acute onset and rapid course of many infectious diseases, and, in particular, the communicability of infectious diseases. The individual fear and community panic associated with infectious diseases often leads to rapid, emotionally driven decision making about public health policies needed to protect the community that may be in conflict with current bioethical principles regarding the care of individual patients. The discussion includes recent examples where dialogue between public health practitioners and medical‐ethicists has helped resolve ethical issues that require us to consider the infected patient as both a victim with individual needs and rights and as a potential vector of disease that is of concern to the community.
Expression of CYP4F12 in Gastrointestinal and Urogenital Epithelia*
Authors: Stark Katarina , Schauer Lydia , Sahlén Göran E. , Ronquist Gunnar , Oliw Ernst H.
Published: April 2004

Abstract: Cytochrome P450 4F12 (CYP4F12) was originally cloned from human liver and small intestine. CYP4F12 can oxidize arachidonic acid, two stable prostaglandin H2 analogues, and an antihistamine, ebastine, but the tissue distribution and catalytic properties of CYP4F12 have not been fully investigated. An antipeptide polyclonal antibody was raised against the C‐terminal of CYP4F12 (PLNVGLQ), evaluated by Western blot analysis and used for immunohistological analysis of 50 human tissues. Western blot analysis of recombinant CYP4F12, expressed in yeast, and microsomal proteins from adult and foetal liver, kidney, placenta at term, seminal vesicles, the prostate gland and purified prostasomes showed that the polyclonal antibody detected a protein of the expected size, ∼60 kDa. CYP4F12 mRNA could be detected in seminal vesicles and prostate gland by reverse transcription‐PCR. Prominent CYP4F12 immunoreactivity occurred, inter alia, in the epithelial cells of the gastrointestinal tract (stomach, small intestine, and colon), collecting tubules, transitional epithelium, ovarian follicles, the endothelium of microvessels of placental villi (first trimester), and epidermis. We screened recombinant CYP4F12 for catalytic activity. Arachidonic acid (20:4n‐6) was hydroxylated at C18 and laurate at C11, but significant amounts of metabolites of 18:2n‐6, 20:3n‐9, 20:5n‐3, 22:5n‐6, and some prostaglandins could not be detected. We conclude that CYP4F12 is widely distributed in gastrointestinal and urogenital epithelia and exhibits a narrow substrate specificity.
Mechanisms of Cardioprotective Effect of Withania somnifera in Experimentally Induced Myocardial Infarction
Authors: Mohanty Ipseeta , Arya Dharamvir Singh , Dinda Amit , Talwar Keval Kishan , Joshi Sujata , Gupta Suresh Kumar
Published: April 2004

Abstract: The present study was designed to evaluate the cardioprotective potential of hydro‐alcoholic extract of Withania somnifera on the basis of haemodynamic, histopathological and biochemical parameters in the isoprenaline‐(isoproterenol) induced myocardial necrosis in rats and to compare with Vitamin E, a known cardioprotective antioxidant. Wistar albino male rats (150–200 g) were divided into six main groups: sham, isoprenaline control, Withania somnifera/Vitamin E control and Withania somnifera/Vitamin E treatment groups. Withania somnifera was administered at doses 25, 50 and 100 mg/kg and Vitamin E at a dose of 100 mg/kg, orally for 4 weeks. On days 29 and 30, the rats in the isoprenaline control and Withania somnifera/Vitamin E treatment groups were given isoprenaline (85 mg/kg), subcutaneously at an interval of 24 hr. On day 31, haemodynamic parameters were recorded and the hearts were subsequently removed and processed for histopathological and biochemical studies. A significant decrease in glutathione (P<0.05), activities of superoxide dismutase, catalase, creatinine phosphokinase and lactate dehydrogenase (P<0.01) as well as increase in lipid peroxidation marker malonyldialdehyde level (P<0.01) was observed in the hearts of isoproterenol control group rats as compared to sham control. However, we have not observed any significant changes in activity of glutathione peroxidase and protein levels. Left ventricular dysfunction was seen as a decrease in heart rate, left ventricular rate of peak positive and negative pressure change and elevated left ventricular end‐diastolic pressure in the control group was recorded. On histopathological examination, myocardial damage was further confirmed. Our data show that Withania somnifera (25, 50 and 100 mg/kg) exerts a strong cardioprotective effect in the experimental model of isoprenaline‐induced myonecrosis in rats. Augmentation of endogenous antioxidants, maintenance of the myocardial antioxidant status and significant restoration of most of the altered haemodynamic parameters may contribute to its cardioprotective effect. Among the different doses studied, Withania somnifera at 50 mg/kg dose produced maximum cardioprotective effect.
Characterization of the Acetaminophen‐Induced Degradation of Cytochrome P450‐3A4 and the Proteolytic Pathway
Authors: Zhang Qing‐Xue , Melnikov Zoya , Feierman Dennis E.
Published: April 2004

Abstract: It has been shown that large doses of acetaminophen can result in increased degradation of the hepatic cytochrome P450 (CYP) enzymes in vivo; however, the proteolytic pathways have not been identified. We found that incubating transfected HepG2 cells that express CYP3A4 or a reconstituted microsomal model containing human liver microsomes and cytosol, high concentrations of acetaminophen could induce a dose‐ and time‐dependent degradation of CYP3A4. In the microsomal model the degradation could be blocked and augmented by the presence of catalase and superoxide dismutase, respectively. Tocopherol could also protect against the acetaminophen‐induced degradation. However, lipid peroxidation assays showed no significant increases in lipid peroxidation products nor was there any protection by propyl gallate. Protease and proteasome inhibitors showed that the proteolytic process was mainly (85%) mediated by the lysosomal pathway, whereas a minor portion (15%) of the degradation was mediated by the proteasomal pathway. Both pepstatin A and anti‐cathepsin D neutralizing antibody decreased acetaminophen‐induced degradation of CYP3A4 in microsomal model systems. Pepstatin A also blocked the acetaminophen‐induced degradation of the CYP3A4 in a transfected HepG2 cell line. Incubating the 3A4 cells in the presence of acetaminophen also increased cathepsin D content and activity. The lysosomal pathway, mainly mediated by cathepsin D, appears to be the major proteolytic pathway involved in the degradation of the P450 enzymes induced by toxic doses of acetaminophen.
Characterization of a Common Susceptibility Locus for Asthma-Related Traits
Authors: Laitinen Tarja , Polvi Anne , Rydman Pia , Vendelin Johanna , Pulkkinen Ville , Salmikangas Paula , Mäkelä Siru , Rehn Marko , Pirskanen Asta , Rautanen Anna , Zucchelli Marco , Gullstén Harriet , Leino Marina , Alenius Harri , Petäys Tuula , Haahtela Tari , Laitinen Annika , Laprise Catherine , Hudson Thomas J. , Laitinen Lauri A. , Kere Juha
Published: April 2004

Susceptibility to asthma depends on variation at an unknown number of genetic loci. To identify susceptibility genes on chromosome 7p, we adopted a hierarchical genotyping design, leading to the identification of a 133-kilobase risk-conferring segment containing two genes. One of these coded for an orphan G protein–coupled receptor named GPRA (G protein–coupled receptor for asthma susceptibility), which showed distinct distribution of protein isoforms between bronchial biopsies from healthy and asthmatic individuals. In three cohorts from Finland and Canada, single nucleotide polymorphism–tagged haplotypes associated with high serum immunoglobulin E or asthma. The murine ortholog of GPRA was up-regulated in a mouse model of ovalbumin-induced inflammation. Together, these data implicate GPRA in the pathogenesis of atopy and asthma.
Neuronal Activity Related to Reward Value and Motivation in Primate Frontal Cortex
Authors: Roesch Matthew R. , Olson Carl R.
Published: April 2004

In several areas of the macaque brain, neurons fire during delayed-response tasks at a rate determined by the value of the reward expected at the end of the trial. The activity of these neurons might be related to the value of the expected reward or to the degree of motivation induced by expectation of the reward. We describe results indicating that the nature of reward-dependent activity varies across areas. Neuronal activity in orbitofrontal cortex represents the value of the expected reward, whereas neuronal activity in premotor cortex reflects the degree of motivation.
Quantifying Stratospheric Ozone in the Upper Troposphere with in Situ Measurements of HCl
Authors: Marcy T. P. , Fahey D. W. , Gao R. S. , Popp P. J. , Richard E. C. , Thompson T. L. , Rosenlof K. H. , Ray E. A. , Salawitch R. J. , Atherton C. S. , Bergmann D. J. , Ridley B. A. , Weinheimer A. J. , Loewenstein M. , Weinstock E. M. , Mahoney M. J.
Published: April 2004

We have developed a chemical ionization mass spectrometry technique for precise in situ measurements of hydrochloric acid (HCl) from a high-altitude aircraft. In measurements at subtropical latitudes, minimum HCl values found in the upper troposphere (UT) were often near or below the detection limit of the measurements (0.005 parts per billion by volume), indicating that background HCl values are much lower than a global mean estimate. However, significant abundances of HCl were observed in many UT air parcels, as a result of stratosphere-to-troposphere transport events. We developed a method for diagnosing the amount of stratospheric ozone in these UT parcels using the compact linear correlation of HCl with ozone found throughout the lower stratosphere (LS). Expanded use of this method will lead to improved quantification of cross-tropopause transport events and validation of global chemical transport models.
How Viruses Enter Animal Cells
Authors: Smith Alicia E. , Helenius Ari
Published: April 2004

Viruses replicate within living cells and use the cellular machinery for the synthesis of their genome and other components. To gain access, they have evolved a variety of elegant mechanisms to deliver their genes and accessory proteins into the host cell. Many animal viruses take advantage of endocytic pathways and rely on the cell to guide them through a complex entry and uncoating program. In the dialogue between the cell and the intruder, the cell provides critical cues that allow the virus to undergo molecular transformations that lead to successful internalization, intra-cellular transport, and uncoating.
Ancient Invasions: From Endosymbionts to Organelles
Authors: Dyall Sabrina D. , Brown Mark T. , Johnson Patricia J.
Published: April 2004

The acquisitions of mitochondria and plastids were important events in the evolution of the eukaryotic cell, supplying it with compartmentalized bioenergetic and biosynthetic factories. Ancient invasions by eubacteria through symbiosis more than a billion years ago initiated these processes. Advances in geochemistry, molecular phylogeny, and cell biology have offered insight into complex molecular events that drove the evolution of endosymbionts into contemporary organelles. In losing their autonomy, endosymbionts lost the bulk of their genomes, necessitating the evolution of elaborate mechanisms for organelle biogenesis and metabolite exchange. In the process, symbionts acquired many host-derived properties, lost much of their eubacterial identity, and were transformed into extraordinarily diverse organelles that reveal complex histories that we are only beginning to decipher.
Reversible Optical Transcription of Supramolecular Chirality into Molecular Chirality
Authors: de Jong Jaap J. D. , Lucas Linda N. , Kellogg Richard M. , van Esch Jan H. , Feringa Ben L.
Published: April 2004

In nature, key molecular processes such as communication, replication, and enzyme catalysis all rely on a delicate balance between molecular and supramolecular chirality. Here we report the design, synthesis, and operation of a reversible, photoresponsive, self-assembling molecular system in which molecular and supramolecular chirality communicate. It shows exceptional stereoselectivity upon aggregation of the molecules during gel formation with the solvent. This chirality is locked by photochemical switching, a process that is subsequently used to induce an inverted chiral supramolecular assembly as revealed by circular dichroism spectroscopy. The optical switching between different chiral aggregated states and the interplay of molecular and supramolecular chirality offer attractive new prospects for the development of molecular memory systems and smart functional materials.
Knowledge, Wisdom, and Luck
Authors: González Cristina
Published: April 2004

The Travels and Adventures of Serendipity
A Study in Sociological Semantics and the Sociology of Science. by Robert K. Merton and Elinor Barber. Princeton University Press, Princeton, NJ, 2004. 341 pp. $29.95, £19.95. ISBN 0-691-11754-3.

In an occasionally cited but unpublished account written in 1958, the authors explore the uses and misuses of the term serendipity since the word's first appearance in 1754--playing particular attention to the importance of the concept in intellectual discovery.
Untangling the Universe
Authors: Trefil James
Published: April 2004

The Fabric of the Cosmos
Space, Time, and the Texture of Reality. by Brian Greene. Knopf, New York, 2004. 583 pp. $28.95, C$39.95. ISBN 0-375-41288-3. Allen Lane (Penguin), London. £25. ISBN 0-7139-9677-3.

Though writing for a broad, lay audience, Greene also offers scientists an excellent exposition of what our current understanding of physics tells us about the universe.
Insulin resistance and hypertension
Authors: Sowers James R.
Published: April 2004

Diminished insulin (Ins) sensitivity is a characteristic feature of various pathological conditions such as the cardiometabolic syndrome, Type 2 diabetes, and hypertension. Persons with essential hypertension are more prone than normotensive persons to develop diabetes, and this propensity may reflect decreased ability of Ins to promote relaxation and glucose transport in vascular and skeletal muscle tissue, respectively. There are increasing data suggesting that ANG II acting through its ANG type 1 receptor inhibits the actions of Ins in vascular and skeletal muscle tissue, in part, by interfering with Ins signally through phosphatidylinositol 3-kinase (PI3K) and its downstream protein kinase B (Akt) signaling pathways. This inhibitory action of ANG II is mediated, in part, through stimulation of RhoA activity and oxidative stress. Activated RhoA and increased reactive oxygen species inhibition of PI3K/Akt signaling results in decreased endothelial cell production of nitric oxide, increased myosin light chain activation with vasoconstriction, and reduced skeletal muscle glucose transport.
Intracellular Ca dynamics in ventricular fibrillation
Authors: Omichi Chikaya , Lamp Scott T. , Lin Shien-Fong , Yang Junzhong , Baher Ali , Zhou Shengmei , Attin Mina , Lee Moon-Hyoung , Karagueuzian Hrayr S. , Kogan Boris , Qu Zhilin , Garfinkel Alan , Chen Peng-Sheng , Weiss James N.
Published: April 2004

In the heart, membrane voltage ( Vm) and intracellular Ca (Cai) are bidirectionally coupled, so that ionic membrane currents regulate Cai cycling and Cai affects ionic currents regulating action potential duration (APD). Although Cai reliably and consistently tracks Vm at normal heart rates, it is possible that at very rapid rates, sarcoplasmic reticulum Cai cycling may exhibit intrinsic dynamics. Non-voltage-gated Cai release might cause local alternations in APD and refractoriness that influence wavebreak during ventricular fibrillation (VF). In this study, we tested this hypothesis by examining the extent to which Cai is associated with Vm during VF. Cai transients were mapped optically in isolated arterially perfused swine right ventricles using the fluorescent dye rhod 2 AM while intracellular membrane potential was simultaneously recorded either locally with a microelectrode (5 preparations) or globally with the voltage-sensitive dye RH-237 (5 preparations). Mutual information (MI) is a quantitative statistical measure of the extent to which knowledge of one variable ( Vm) predicts the value of a second variable (Cai). MI was high during pacing and ventricular tachycardia (VT; 1.13 ± 0.21 and 1.69 ± 0.18, respectively) but fell dramatically during VF (0.28 ± 0.06, P < 0.001). Cai at sites 4–6 mm apart also showed decreased MI during VF (0.63 ± 0.13) compared with pacing (1.59 ± 0.34, P < 0.001) or VT (2.05 ± 0.67, P < 0.001). Spatially, Cai waves usually bore no relationship to membrane depolarization waves during nonreentrant fractionated waves typical of VF, whereas they tracked each other closely during pacing and VT. The dominant frequencies of Vm and Cai signals analyzed by fast Fourier transform were similar during VT but differed significantly during VF. Cai is closely associated with Vm closely during pacing and VT but not during VF. These findings suggest that during VF, non-voltage-gated Cai release events occur and may influence wavebreak by altering Vm and APD locally.
Endogenous VEGF-A is responsible for mitogenic effects of MCP-1 on vascular smooth muscle cells
Authors: Parenti Astrid , Bellik Lydia , Brogelli Laura , Filippi Sandra , Ledda Fabrizio
Published: April 2004

Vessel wall remodeling is a complex phenomenon in which the loss of differentiation of vascular smooth muscle cells (VSMCs) occurs. We investigated the role of rat macrophage chemoattractant protein (MCP)-1 on rat VSMC proliferation and migration to identify the mechanism(s) involved in this kind of activity. Exposure to very low concentrations (1–100 pg/ml) of rat MCP-1 induced a significant proliferation of cultured rat VSMCs assessed as cell duplication by the counting of total cells after exposure to test substances. MCP-1 stimulated VSMC proliferation and migration in a two-dimensional lateral sheet migration of adherent cells in culture. Endogenous vascular endothelial growth factor-A (VEGF-A) was responsible for the mitogenic activity of MCP-1, because neutralizing anti-VEGF-A antibody inhibited cell proliferation in response to MCP-1. On the contrary, neutralizing anti-fibroblast growth factor-2 and anti-platelet-derived growth factor-bb antibodies did not affect VSMC proliferation induced by MCP-1. RT-PCR and Western blot analyses showed an increased expression of either mRNA or VEGF-A protein after MCP-1 activation (10–100 pg/ml), whereas no fms-like tyrosine kinase (Flt)-1 receptor upregulation was observed. Because we have previously demonstrated that hypoxia (3% O2) can enhance VSMC proliferation induced by VEGF-A through Flt-1 receptor upregulation, the effects of hypoxia on the response of VSMCs to MCP-1 were investigated. Severe hypoxia (3% O2) potentiated the growth-promoting effect of MCP-1, which was able to significantly induce cell proliferation even at a concentration as low as 0.1 pg/ml. These findings demonstrate that low concentrations of rat MCP-1 can directly promote rat VSMC proliferation and migration through the autocrine production of VEGF-A.
Myocardial density and composition: a basis for calculating intracellular metabolite concentrations
Authors: Vinnakota Kalyan C. , Bassingthwaighte James B.
Published: April 2004

Systems for describing myocardial cellular metabolism with appropriate thermodynamic constraints on reactions have to be on the basis of estimates of intracellular and mitochondrial concentrations of metabolites as driving forces for reactions. This requires that tissue composition itself must be modeled, but there is marked inconsistency in the literature and no full data set on hearts of any species. To formulate a self-consistent set of information on the densities, contents, or concentrations of chemical components and volumes of tissue spaces, we drew on information mostly on rats. From the data on densities, volumes, volume fractions, and mass fractions observed mainly on left ventricular myocardium, cytoplasm, and mitochondria and from morphometric data on cellular components and the vasculature, we constructed a matrix based on conservation laws for density, volume, and constituent composition. The four constituents were water, protein, fat, and solutes (or ash). To take into account the variances in the observed data sets, we used a constrained nonlinear least squares optimization to minimize the differences between the final results and the data sets. The results provide a detailed estimate of cardiac tissue composition, previously unavailable, for the translation of whole tissue concentrations or concentrations per gram protein into estimated local concentrations that are relevant to reaction processes. An example is that the concentrations of phosphocreatine and ATP in cytosolic water space are twice as high as their mean tissue concentrations. This conservation optimization method is applicable to any tissue or organ.
Electrotonic load triggers remodeling of repolarizing current Ito in ventricle
Authors: Libbus Imad , Wan Xiaoping , Rosenbaum David S.
Published: April 2004

A change in activation sequence electrically remodels ventricular myocardium, causing persistent changes in repolarizing currents (T-wave memory). However, the underlying mechanism for triggering activation sequence-dependent remodeling is unknown. Optical action potentials were mapped with high resolution from the epicardial surface of the arterially perfused canine wedge preparation ( n = 23) during 30 min of baseline endocardial stimulation, followed by 40 min of epicardial stimulation, and, finally, restoration of endocardial stimulation. Immediately after the change from endocardial to epicardial stimulation, phase 1 notch amplitude of epicardial cells was attenuated by 74 ± 8% ( P < 0.001) compared with baseline and continued to diminish during the period of epicardial pacing, suggesting progressive remodeling of the transient outward current ( Ito). When endocardial pacing was restored, notch amplitude did not immediately recover but remained attenuated by 23 ± 10% ( P < 0.001), also consistent with a remodeling effect. Peak Ito current measured from isolated epicardial myocytes changed by 12 ± 4% ( P < 0.025), providing direct evidence for Ito remodeling occurring on a surprisingly short time scale. The mechanism for triggering remodeling of Ito was a significant reduction (by 14 ± 4%, P < 0.001) of upstroke amplitude in epicardial cells during epicardial stimulation. Reduction in upstroke amplitude during epicardial pacing was explained by electrotonic load on epicardial cells by fully repolarized downstream endocardial cells. These data suggest a novel mechanism for triggering electrical remodeling in the ventricle. Electrotonic load imposed by a change in activation sequence reduces upstroke amplitude, which, in turn, attenuates Ito according to its known voltage-dependent properties, triggering downregulation of current.
Disodium cromoglycate stabilizes mast cell degranulation while reducing the number of hemoglobin-induced microvascular leaks in rat mesentery
Authors: Ginsburg Maxwell I. , Baldwin Ann L.
Published: April 2004

Blood substitutes, such as diaspirin cross-linked Hb (DBBF-Hb), have been considered for use during blood transfusions. Unfortunately, bolus injection of modified Hb has been shown to rapidly increase the leakage of microvessels to plasma albumin. This effect may result from production of excess reactive oxygen species (ROS) and could be linked to the observed increase in degranulated mast cells (DMC). Disodium cromoglycate (cromolyn) stabilizes mast cells and therefore might minimize the venular permeability in the rat mesentery. In 10 anesthetized Sprague-Dawley rats, the mesenteric preparation was continuously suffused with cromolyn while the microvasculature was filled with DBBF-Hb solution (10 mg/ml) for 10 min. Six animals received cromolyn pretreatment [two intravascular injections over 30 min ( experiment A)] and four animals received pretreatment with 2% HEPES-buffered saline (HBS)-BSA ( experiment B). Two more animals were pretreated with HBS-BSA without DBBF-Hb infusion but with cromolyn suffusion ( experiment C). Another set of experiments was performed on five animals without cromolyn suffusion or any pretreatment but with DBBF-Hb infusion ( experiment D). All groups then received a 1-min perfusion of FITC-albumin, fixation for 60 min, and microscopic examination. Experiments A and B demonstrated a significant reduction in the number of venular leaks and DMC compared with experiment D, but not in the area of venular leaks. These results suggest mast cell degranulation is not a major contributor to microvascular leakage induced by DBBF-Hb.
Molecular cloning, functional analysis, and RNA expression analysis of connexin45.6: a zebrafish cardiovascular connexin
Authors: Christie Tara L. , Mui Rickie , White Thomas W. , Valdimarsson Gunnar
Published: April 2004

In the vertebrate cardiovascular system, gap junctions function in intercellular communication essential for both the coordinated propagation of the heartbeat and the control of vasomotor responses in the vascular system. Connexins, the protein subunits of gap junctions, are coded by a multigene family. In this study, a connexin gene (zfCx45.6), which exhibits 53% amino acid identity to chick Cx42, was cloned from zebrafish genomic DNA. With the use of the LN54 radiation hybrid panel, zfCx45.6 was mapped to zebrafish linkage group 9. Northern blots and RT-PCR revealed the presence of zfCx45.6 mRNA in the embryo before 2 h postfertilization (hpf) and then again beginning at about 12 hpf, after which time no major changes in relative expression levels were detected. In the adult, zfCx45.6 mRNA continued to be detected in the heart, as well as the brain, liver, and ovary, but not the lens. Whole mount in situ hybridization revealed zfCx45.6 mRNA was expressed at high levels in the major vessels of the entire embryo and in both the atrium and ventricle of the adult heart. Expression of zfCx45.6 channels in paired Xenopus oocytes produced high levels of intercellular coupling that was voltage sensitive. With the previous isolation of zebrafish Cx43 and Cx43.4, zebrafish orthologues have now been isolated for three of the four connexins expressed in the mammalian cardiovascular system.
A new method to denude the endothelium without damage to media: structural, functional, and biomechanical validation
Authors: Lu Xiao , Guo Xiaomei , Linares Carlos , Kassab Ghassan S.
Published: April 2004

The intimial thickening that occurs in human and animal atherogenesis can be induced by mechanical injury to the endothelium. The objective of the present study was to develop a new method to induce arterial endothelial injury without damage to the media for future investigations of mechanisms of intimal thickening and atherogenesis. A specifically designed catheter was inserted into the common femoral artery of Wistar rats ( n = 9) through an arteriotomic mouth. After application of Tyrode solution containing 0.14 M KCl on the surface of the vessel, the vessel contracted onto the catheter. The catheter was then moved back and forth to scrape away the endothelium. The left common femoral artery of the same rat was subjected to the standard balloon injury model. The two models were evaluated structurally, functionally, and biomechanically. Structurally, we verified that both techniques remove the endothelium, but the balloon method damages the media. Functionally, we examined the contractile response of the artery to [K+] and norepinephrine 2 days after the denudation. We found that the right femoral artery underwent contraction in response to [K+], whereas the left artery did not. Furthermore, neither artery responded to norepinephrine. Biomechanically, we measured the pressure-diameter relationship and the zero-stress state of the vessel and computed the stress-strain relation. The circumferential stretch ratios at 120 mmHg were 1.38 ± 0.08 for the control, 1.41 ± 0.08 ( P > 0.05) for the new method, and 1.56 ± 0.09 for the balloon injury ( P < 0.05). The opening angles at the zero-stress state were 113 ± 21° for the control, 102 ± 18° for the new method ( P > 0.05), and 8 ± 13° for the balloon injury ( P < 0.001). In conclusion, the new method removes the endothelium while maintaining the structure, contractile function, and biomechanical properties of the vessel.
Myocardial ischemia induces the release of substance P from cardiac afferent neurons in rat thoracic spinal cord
Authors: Hua Fang , Ricketts Brian A. , Reifsteck Angela , Ardell Jeffrey L. , Williams Carole A.
Published: April 2004

Antibody-coated microprobes were inserted into the thoracic (T3–4) spinal cord in urethane-anesthetized Sprague-Dawley rats to detect the differences in the release of immunoreactive substance P-like (irSP) substances in response to differential activation of cardiac nociceptive sensory neurons (CNAN). CNAN were stimulated either by intrapericardial infusion of an inflammatory ischemic exudate solution (IES) containing algogenic substances (i.e., 10 mM each of adenosine, bradykinin, prostaglandin E2, and 5-hydroxytryptamine), or by transient occlusion of the left anterior descending coronary artery (CoAO). There was widespread basal release of irSP from the thoracic spinal cord. Stimulation of the CNAN by IES did not alter the pattern of release of irSP. Conversely, CoAO augmented the release of irSP from T3–4 spinal segments from laminae I–VII. This CoAO-induced irSP release was eliminated after thoracic dorsal rhizotomy. These results indicate that heterogeneous activation of cardiac afferents, as with focal coronary artery occlusion, represents an optimum input for activation of the cardiac neuronal hierarchy and for the resultant perception of angina. Excessive stimulation of cardiac nociceptive afferent neurons elicited during regional coronary artery occlusion involves the release of SP in the thoracic spinal cord and suggests that local spinal cord release of SP may be involved in the neural signaling of angina.
Action potential modulation of connexin40 gap junctional conductance
Authors: Lin Xianming , Veenstra Richard D.
Published: April 2004

Connexin40 (Cx40) is abundantly expressed in the atrial myocardium, ventricular conduction system, and vascular endothelial and smooth muscle cells of the mammalian cardiovascular system. Rapid conduction through cardiac tissues depends on electrotonic transfer of the action potential between neighboring cells. To determine whether transjunctional voltages ( Vj) elicited by an action potential can modulate conductance of Cx40 gap junctions, simulated myocardial action potentials were applied as voltage-clamp waveforms to Cx40 gap junctions expressed in mouse neuro2A (N2A) cells. Junctional currents resembled the action potential morphology but declined by >50% from peak to near-constant plateau values. Kinetics of Cx40 voltage gating were examined at peak voltages ≥100 mV, and decay time constants changed e-fold per 17.6 mV for Vj > ±40 mV. Junctional conductance recovered during phase 3 repolarization and early diastole to initial values. These phasic changes in junctional conductance were due to rapid decay kinetics, increasing to tens of milliseconds at peak Vj of 130 mV, and the increase in the steady-state conductance curve as Vj returned toward 0 mV. Time-dependent conductance curves for Cx40 were modeled with one inactivation and two recovery Vj-dependent components. There was a temporal correlation between development of conduction delay or block and the inactivation phase of junctional conductance. Likewise, recovery of junctional conductance was coincident with recovery from refractoriness, suggesting that gap junctions may play a role in the genesis and propagation of cardiac arrhythmias.
DITPA stimulates arteriolar growth and modifies myocardial postinfarction remodeling
Authors: Zheng Wei , Weiss Robert M. , Wang Xinguo , Zhou Ruifeng , Arlen Angie M. , Lei Li , Lazartigues Eric , Tomanek Robert J.
Published: April 2004

Myocardial infarction (MI) is characterized by ventricular remodeling, hypertrophy of the surviving myocardium, and an insufficient angiogenic response. Thyroxine is a powerful stimulus for myocardial angiogenesis. Male rats that underwent coronary artery ligation and subsequent MI were given 3,5-diiodothyropropionic acid (DITPA; MI+DITPA group) during a 3-wk period. We evaluated ventricular remodeling using echocardiography and histology and myocardial vessel growth using image analysis. Protein expression was assessed using Western blotting and immunohistochemistry. This study tested the hypothesis that the thyroxine analog DITPA facilitates angiogenesis and influences postinfarction remodeling in the surviving hypertrophic myocardium. The increase in the region of akinesis (infarct expansion) was blunted in the MI+DITPA rats compared with the MI group (3 vs. 21%); the treated rats had smaller percent increases in the left ventricular (LV) volume (64 ± 14 vs. 95 ± 12) and the LV volume-to-mass ratio (47 ± 13 vs. 84 ± 10) as well as a blunted decrease in ejection fraction (–9 ± 8 vs. –30 ± 7%). Arteriolar length density was higher after treatment in the largest (>50% of the free wall) infarcts (64 ± 3 vs. 43 ± 7). Angiogenic growth factors [vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF)] and the angiopoietin receptor tyrosine kinase with immunoglobulin and epidermal growth factor homology domains (Tie-2) values were elevated during the first week after infarction. DITPA did not cause additional increases in VEGF or Tie-2 values but did induce an increase in bFGF value after 3 days of treatment. This study provides the first evidence for an anatomical basis, i.e., attenuated ventricular remodeling and arteriolar growth, for improved function attributed to DITPA therapy of the infarcted heart. The favorable influences of DITPA on LV remodeling after large infarction are principally due to border zone preservation.
Timing of cardiac contraction in humans mapped by high-temporal-resolution MRI tagging: early onset and late peak of shortening in lateral wall
Authors: Zwanenburg J. J. M. , Götte M. J. W. , Kuijer J. P. A. , Heethaar R. M. , van Rossum A. C. , Marcus J. T.
Published: April 2004

Mechanical asynchrony is an important parameter in predicting the response to cardiac resynchronization therapy, but detailed knowledge of cardiac contraction timing in healthy persons is scarce. In this work, timing of cardiac contraction was mapped in 17 healthy subjects with high-temporal-resolution (14 ms) MRI myocardial tagging and strain analysis. Both the onset time of circumferential shortening ( Tonset) in early systole and the time of peak circumferential shortening ( Tpeak) at end systole were determined. The onset of shortening width (time needed for 20–90% of the left ventricle to start shortening) was small (35 ± 9 ms). A distinct spatial pattern for Tonsetwas found, with earliest onset in the lateral wall and latest onset in the septum ( P = 0.001). Compared with Tonset, Tpeakhad a larger width (121 ± 22 ms) and an opposite spatial pattern, with peak shortening occurring earlier in the septum than in the lateral wall ( P < 0.001). Postsystolic shortening ( Tpeaklater than aortic valve closure; P < 0.05) was observed in 13 of the 30 cardiac segments, mainly in the lateral and basal segments. Shortening in these segments continued 58 ± 14 ms after aortic valve closure, during which circumferential shortening increased from 16.9 ± 1.2% to 20.0 ± 1.5%. Maps of the timing of contraction in normal subjects may serve as a reference in detecting mechanical asynchrony due to intraventricular conduction defects or ischemia.
Endothelial cell P-selectin mediates a proinflammatory and prothrombogenic phenotype in cerebral venules of sickle cell transgenic mice
Authors: Wood Katherine C. , Hebbel Robert P. , Granger D. Neil
Published: April 2004

Whereas the adhesion of leukocytes and erythrocytes to vascular endothelium has been implicated in the vasooclusive events associated with sickle cell disease, the role of platelet-vessel wall interactions in this process remains undefined. The objectives of this study were to: 1) determine whether the adhesion of platelets and leukocytes in cerebral venules differs between sickle cell transgenic (βS) mice and their wild-type (WT) counterparts (C57Bl/6) under both resting and posthypoxic conditions, and 2) define the contributions of P-selectin to these adhesion processes. Animals were anesthetized, and platelet and leukocyte interactions with endothelial cells of cerebral postcapillary venules were monitored and quantified using intravital fluorescence microscopy in WT, βS, and chimeric mice produced by transplanting bone marrow from WT or βSmice into WT or P-selectin-deficient (P-sel–/–) mice. Platelet and leukocyte adhesion to endothelial cells in both unstimulated and posthypoxic βSmice were significantly elevated over WT levels. Chimeric mice involving bone marrow transfer from βSmice to P-sel–/–mice exhibited a profound attenuation of both platelet and leukocyte adhesion compared with βSbone marrow transfer to WT mice. These findings indicate that βSmice assume both an inflammatory and prothrombogenic phenotype, with endothelial cell P-selectin playing a major role in mediating these microvascular responses.
Onset of pulsatile pressure causes transiently increased filtration through artery wall
Authors: Alberding Jonathan P. , Baldwin Ann L. , Barton Jennifer K. , Wiley Elizabeth
Published: April 2004

Convective fluid motion through artery walls aids in the transvascular transport of macromolecules. Although many measurements of convective filtration have been reported, they were all obtained under constant transmural pressure. However, arterial pressure in vivo is pulsatile. Therefore, experiments were designed to compare filtration under steady and pulsatile pressure conditions. Rabbit carotid arteries were cannulated and excised from male New Zealand White rabbits anesthetized with pentobarbitol sodium (30 mg/kg iv administered). Hydraulic conductance was measured in cannulated excised rabbit carotid arteries at steady pressure. Next, pulsatile pressure trains were applied within the same vessels, and, simultaneously, arterial distension was monitored using Optical coherence tomography (OCT). For each pulse train, the volume of fluid lost through filtration was measured (subtracting volume change due to residual distension) and compared with that predicted from steady pressure measurements. At 60- and 80-mmHg baseline pressures, the experimental filtration volumes were significantly increased compared with those predicted for steady pressure ( P < 0.05). OCT demonstrated that the excess fluid volume loss was significantly greater than the volume that would be lost through residual distension ( P < 0.05). After 30 s, the magnitude of the excess of fluid loss was reduced. These results suggest that sudden onset of pulsatile pressure may cause changes in arterial interstitial hydration.
Cardiac sympathetic afferent stimulation impairs baroreflex control of renal sympathetic nerve activity in rats
Authors: Gao Lie , Zhu Zhen , Zucker Irving H. , Wang Wei
Published: April 2004

It is well known that cardiac sympathetic afferent reflexes contribute to increases in sympathetic outflow and that sympathetic activity can antagonize arterial baroreflex function. In this study, we tested the hypothesis that in normal rats, chemical and electrical stimulation of cardiac sympathetic afferents results in a decrease in the arterial baroreflex function by increasing sympathetic nerve activity. Under α-chloralose (40 mg/kg) and urethane (800 mg/kg ip) anesthesia, renal sympathetic nerve activity, mean arterial pressure, and heart rate were recorded. The arterial baroreceptor reflex was evaluated by infusion of nitroglycerin (25 μg iv) and phenylephrine (10 μg iv). Left ventricular epicardial application of capsaicin (0.4 μg in 2 μl) blunted arterial baroreflex function by 46% (maximum slope 3.5 ± 0.3 to 1.9 ± 0.2%/mmHg, P < 0.01). When the central end of the left cardiac sympathetic nerve was electrically stimulated (7 V, 1 ms, 20 Hz), the sensitivity of the arterial baroreflex was similarly decreased by 42% (maximum slope 3.2 ± 0.3 to 1.9 ± 0.4%/mmHg; P < 0.05). Pretreatment with intracerebroventricular injection of losartan (500 nmol in 1 μl of artificial cerebrospinal fluid) completely prevented the impairment of arterial baroreflex function induced by electrical stimulation of the central end of the left cardiac sympathetic nerve (maximum slope 3.6 ± 0.4 to 3.1 ± 0.5%/mmHg). These results suggest that the both chemical and electrical stimulation of the cardiac sympathetic afferents reduces arterial baroreflex sensitivity and the impairment of arterial baroreflex function induced by cardiac sympathetic afferent stimulation is mediated by central angiotensin type 1 receptors.
On defining total lung capacity in the mouse
Authors: Soutiere Shawn E. , Mitzner Wayne
Published: April 2004

Maximal lung volume or total lung capacity in experimental animals is dependent on the pressure to which the lungs are inflated. Although 25-30 cmH2O are nominally used for such inflations, mouse pressure-volume (P-V) curves show little flattening on inflation to those pressures. In the present study, we examined P-V relations and mean alveolar chord length in three strains (C3H/HeJ, A/J, and C57BL/6J) at multiple inflation pressures. Mice were anesthetized, and their lungs were degassed in vivo by absorption of 100% O2. P-V curves were then recorded in situ with increasing peak inflation pressure in 10-cmH2O increments up to 90 cmH2O. Lungs were quickly frozen at specific pressures for morphometric analysis. The inflation limbs never showed the appearance of a plateau, with lung volume increasing 40-60% as inflation pressure was increased from 30 to 60 cmH2O. In contrast, parallel flat deflation limbs were always observed, regardless of the inflation pressure, indicating that the presence of a flat deflation curve cannot be used to justify measurement of total lung capacity in mice. Alveolar size increased monotonically with increasing pressure in all strains, and there was no evidence of irreversible lung damage from these inflations to high pressures. These results suggest that the mouse lung never reaches a maximal volume, even up to nonphysiological pressures >80 cmH2O.