bluuebunny/crossref_metadata_2025 huggingface dataset:
Gene Products of the
hupGHIJ
Operon Are Involved in Maturation of the Iron-Sulfur Subunit of the [NiFe] Hydrogenase from
Rhizobium leguminosarum
bv. viciae
Authors: Manyani Hamid , Rey Luis , Palacios José M. , Imperial Juan , Ruiz-Argüeso Tomás
Published: September 2005

In the present study, we investigate the functions of the
hupGHIJ
operon in the synthesis of an active [NiFe] hydrogenase in the legume endosymbiont
Rhizobium leguminosarum
bv. viciae. These genes are clustered with 14 other genes including the hydrogenase structural genes
hupSL
. A set of isogenic mutants with in-frame deletions (Δ
hupG
, Δ
hupH
, Δ
hupI
, and Δ
hupJ
) was generated and tested for hydrogenase activity in cultures grown at different oxygen concentrations (0.2 to 2.0%) and in symbiosis with peas. In free-living cultures, deletions in these genes severely reduced hydrogenase activity. The Δ
hupH
mutant was totally devoid of hydrogenase activity at any of the O
2
concentration tested, whereas the requirement of
hupGIJ
for hydrogenase activity varied with the O
2
concentration, being more crucial at higher pO
2
. Pea bacteroids from the mutant strains affected in
hupH, hupI
, and
hupJ
exhibited reduced (20 to 50%) rates of hydrogenase activity compared to the wild type, whereas rates were not affected in the
ΔhupG
mutant. Immunoblot experiments with HupL- and HupS-specific antisera showed that free-living cultures from
ΔhupH, ΔhupI
, and
ΔhupJ
mutants synthesized a fully processed mature HupL protein and accumulated an unprocessed form of HupS (pre-HupS). Both the mature HupL and the pre-HupS forms were located in the cytoplasmic fraction of cultures from the
ΔhupH
mutant. Affinity chromatography experiments revealed that cytoplasmic pre-HupS binds to the HupH protein before the pre-HupS-HupL complex is formed. From these results we propose that
hupGHIJ
gene products are involved in the maturation of the HupS hydrogenase subunit.
The
Mycobacterium tuberculosis
Extracytoplasmic-Function Sigma Factor SigL Regulates Polyketide Synthases and Secreted or Membrane Proteins and Is Required for Virulence
Authors: Hahn Mi-Young , Raman Sahadevan , Anaya Mauricio , Husson Robert N.
Published: September 2005

Mycobacterium tuberculosis sigL
encodes an extracytoplasmic function (ECF) sigma factor and is adjacent to a gene for a membrane protein (Rv0736) that contains a conserved HXXXCXXC sequence. This motif is found in anti-sigma factors that regulate several ECF sigma factors, including those that control oxidative stress responses. In this work, SigL and Rv0736 were found to be cotranscribed, and the intracellular domain of Rv0736 was shown to interact specifically with SigL, suggesting that Rv0736 may encode an anti-sigma factor of SigL. An
M. tuberculosis sigL
mutant was not more susceptible than the parental strain to several oxidative and nitrosative stresses, and
sigL
expression was not increased in response to these stresses. In vivo,
sigL
is expressed from a weak SigL-independent promoter and also from a second SigL-dependent promoter. To identify SigL-regulated genes,
sigL
was overexpressed and microarray analysis of global transcription was performed. Four small operons,
sigL
(Rv0735)-Rv0736,
mpt53
(Rv2878c)-Rv2877c,
pks10
(Rv1660)-
pks7
(Rv1661), and Rv1139c-Rv1138c, were among the most highly upregulated genes in the
sigL
-overexpressing strain. SigL-dependent transcription start sites of these operons were mapped, and the consensus promoter sequences TGAACC in the −35 region and CGTgtc in the −10 region were identified. In vitro, purified SigL specifically initiated transcription from the promoters of
sigL, mpt53
, and
pks10
. Additional genes, including four PE_PGRS genes, appear to be regulated indirectly by SigL. In an in vivo murine infection model, the
sigL
mutant strain showed marked attenuation, indicating that the
sigL
regulon is important in
M. tuberculosis
pathogenesis.
Biosynthesis of Active
Bacillus subtilis
Urease in the Absence of Known Urease Accessory Proteins
Authors: Kim Jong Kyong , Mulrooney Scott B. , Hausinger Robert P.
Published: September 2005

Bacillus subtilis
contains urease structural genes but lacks the accessory genes typically required for GTP-dependent incorporation of nickel. Nevertheless,
B. subtilis
was shown to possess a functional urease, and the recombinant enzyme conferred low levels of nickel-dependent activity to
Escherichia coli
. Additional investigations of the system lead to the suggestion that
B. subtilis
may use unidentified accessory proteins for in vivo urease activation.
YrxA Is the Transcriptional Regulator That Represses De Novo NAD Biosynthesis inBacillus subtilis
Authors: Rossolillo Paola , Marinoni Ilaria , Galli Elisa , Colosimo Anna , Albertini Alessandra M.
Published: September 2005

The first genetic, in vivo, and in vitro evidences that YrxA is the regulator of NAD de novo biosynthesis inBacillus subtilisare hereby reported. The protein is essential to the transcription repression of the divergent operonsnadBCAandnifS-yrxAin the presence of nicotinic acid and binds to their shared operator-promoter region.
The Recombinant Phage Lysin LysK Has a Broad Spectrum of Lytic Activity against Clinically Relevant Staphylococci, Including Methicillin-Resistant
Staphylococcus aureus
Authors: O'Flaherty S. , Coffey A. , Meaney W. , Fitzgerald G. F. , Ross R. P.
Published: September 2005

This study concerns the cloning, characterization, and expression of the lysin (LysK) from staphylococcal phage K in
Lactococcus lactis
. Lactococcal lysates containing recombinant LysK were found to inhibit a range of different species of staphylococci isolated from bovine and human infection sources, including methicillin-resistant
Staphylococcus aureus
. LysK thus has potential as an antimicrobial for applications in the prevention and/or treatment of infections caused by staphylococci.
Electric Properties of Cyanoborane Isomers
Authors: Medveď Miroslav , Černušák Ivan , Kedžuch Stanislav , Noga Jozef
Published: September 2005

Cyanoborane isomers and their acyclic and cyclic oligomers serve as useful models for studying properties of molecules with alternating electron-rich and electron-deficient groups. Static electric properties including electronic dipole moment, polarizability, first and second hyperpolarizabilities of three stable isomeric monomers - boranylmethanenitrile, borazirene and 1-(methanylidyne)borazan-1-ium-2-ide - have been calculated at the MP2, CCSD and CCSD(T) levels using various basis sets. In addition, frequency-dependent (hyper)- polarizabilities of the most stable isomer have been evaluated via the CCSD response theory.
Practical virtue ethics: healthcare whistleblowing and portable digital technology
Authors: Bolsin S , Faunce T , Oakley J
Published: September 2005

Medical school curricula and postgraduate education programmes expend considerable resources teaching medical ethics. Simultaneously, whistleblowers’ agitation continues, at great personal cost, to prompt major intrainstitutional and public inquiries that reveal problems with the application of medical ethics at particular clinical “coalfaces”.

Virtue ethics, emphasising techniques promoting an agent’s character and instructing their conscience, has become a significant mode of discourse in modern medical ethics. Healthcare whistleblowers, whose complaints are reasonable, made in good faith, in the public interest, and not vexatious, we argue, are practising those obligations of professional conscience foundational to virtue based medical ethics. Yet, little extant virtue ethics scholarship seriously considers the theoretical foundations of healthcare whistleblowing.

The authors examine whether healthcare whistleblowing should be considered central to any medical ethics emphasising professional virtues and conscience. They consider possible causes for the paucity of professional or academic interest in this area and examine the counterinfluence of a continuing historical tradition of guild mentality professionalism that routinely places relationships with colleagues ahead of patient safety.

Finally, it is proposed that a virtue based ethos of medical professionalism, exhibiting transparency and sincerity with regard to achieving uniform quality and safety of health care, may be facilitated by introducing a technological imperative using portable computing devices. Their use by trainees, focused on ethical competence, provides the practical face of virtue ethics in medical education and practice. Indeed, it assists in transforming the professional conscience of whistleblowing into a practical, virtue based culture of self reporting and personal development.
ROBUST HIGH ORDER NON-CONFORMING FINITE ELEMENT FORMULATION FOR TIME DOMAIN FLUID-STRUCTURE INTERACTION
Authors: DIAZ JULIEN , JOLY PATRICK
Published: September 2005

In this paper we present various numerical methods for solving time-dependent fluid-structure interaction problem in two or three dimensions that we claim to be efficient, robust and highly accurate. These methods, based on mixed variational formulations, are explicit and conservative and can be of arbitrary high order in space. Their accuracy will be illustrated via a comparison with analytical solutions in simple configuration.
ANALYTIC PRECONDITIONERS FOR THE BOUNDARY INTEGRAL SOLUTION OF THE SCATTERING OF ACOUSTIC WAVES BY OPEN SURFACES
Authors: ANTOINE XAVIER , BENDALI ABDERRAHMANE , DARBAS MARION
Published: September 2005

This study is devoted to some numerical issues in the boundary integral solution of the scattering of an acoustic wave by an open surface. More precisely, it deals with the construction of a cheap analytical preconditioner to enhance the iterative solving of this kind of equation. Detailed attention is paid to bring out the reasons that make this construction much more difficult than for closed surfaces. This preconditioner is carefully tested and compared to two more usual ones for two and three dimensional problems. It is shown that this preconditioner provides a cheap and efficient tool making reliable the iterative solving. The discussion also precisely brings out the issues where further studies are still needed to improve its efficiency.
ALGEBRAIC WAY TO DERIVE ABSORBING BOUNDARY CONDITIONS FOR THE HELMHOLTZ EQUATION
Authors: MAGOULÈS FRÉDÉRIC , ROUX FRANÇOIS-XAVIER , SERIES LAURENT
Published: September 2005

This paper is dedicated to the optimal convergence properties of a domain decomposition method involving two-Lagrange multipliers at the interface between the subdomains and additional augmented interface operators. Most methods for optimizing these augmented interface operators are based on the discretization of continuous approximations of the optimal transparent operators.1–5 Such approach is strongly linked to the continuous equation, and to the discretization scheme. At the discrete level, the optimal transparent operator can be proved to be equal to the Schur complement of the outer subdomain. Our idea consists of approximating directly the Schur complement matrix with purely algebraic techniques involving local condensation of the subdomain degree of freedom on small patch defined on the interface between the subdomains. The main advantage of such approach is that it is much more easy to implement in existing code without any information on the geometry of the interface and of the finite element formulation used. Such technique leads to a so-called "black box" for the users. Convergence results and parallel efficiency of this new and original algebraic optimization technique of the interface operators are presented for acoustics applications.
ROLE OF ABCG2/BCRP IN BIOLOGY AND MEDICINE
Authors: Krishnamurthy P. , Schuetz J.D.
Published: September 2005

▪ Abstract  The protein variously named ABCG2/BCRP/MXR/ABCP is a recently described ATP-binding cassette (ABC) transporter originally identified by its ability to confer drug resistance that is independent of Mrp1 (multidrug-resistance protein 1) and Pgp (P-glycoprotein). Unlike Mrp1 and Pgp, ABCG2 is a half-transporter that must homodimerize to acquire transport activity. ABCG2 is found in a variety of stem cells and may protect them from exogenous and endogenous toxins. ABCG2 expression is upregulated under low-oxygen conditions, consistent with its high expression in tissues exposed to low-oxygen environments. ABCG2 interacts with heme and other porphyrins and protects cells and/or tissues from protoporphyrin accumulation under hypoxic conditions. Individuals who carry ABCG2 alleles that have impaired function may be more susceptible to porphyrin-induced toxicity. Abcg2 knock-out models have allowed in vivo studies of Abcg2 function in host and cellular defense. In combination with immunohistochemical analyses, these studies have revealed how ABCG2 influences the absorption, distribution, and excretion of drugs and cytotoxins.
ENDOTHELIAL-CARDIOMYOCYTE INTERACTIONS IN CARDIAC DEVELOPMENT AND REPAIR
Authors: Hsieh Patrick C.H. , Davis Michael E. , Lisowski Laura K. , Lee Richard T.
Published: September 2005

▪ Abstract  Communication between endothelial cells and cardiomyocytes regulates not only early cardiac development but also adult cardiomyocyte function, including the contractile state. In the normal mammalian myocardium, each cardiomyocyte is surrounded by an intricate network of capillaries and is next to endothelial cells. Cardiomyocytes depend on endothelial cells not only for oxygenated blood supply but also for local protective signals that promote cardiomyocyte organization and survival. While endothelial cells direct cardiomyocytes, cardiomyocytes reciprocally secrete factors that impact endothelial cell function. Understanding how endothelial cells communicate with cardiomyocytes will be critical for cardiac regeneration, in which the ultimate goal is not simply to improve systolic function transiently but to establish new myocardium that is both structurally and functionally normal in the long term.
SGK KINASES AND THEIR ROLE IN EPITHELIAL TRANSPORT
Authors: Loffing Johannes , Flores Sandra Y. , Staub Olivier
Published: September 2005

▪ Abstract  The serum/glucocorticoid-induced kinase Sgk1 plays an important role in the regulation of epithelial ion transport. This kinase is very rapidly regulated at the transcriptional level as well as via posttranslational modifications involving phosphorylation by the MAP or PI-3 kinase pathways and/or ubiquitylation. Although Sgk1 is a cell survival kinase, its primary role likely concerns the regulation of epithelial ion transport, as suggested by the phenotype of Sgk1-null mice, which display a defect in Na+ homeostasis owing to disturbed renal tubular Na+ handling. In this review we first discuss the molecular, cellular, and regulatory aspects of Sgk1 and its paralogs. We then discuss its roles in the physiology and pathophysiology of epithelial ion transport.
Hexosamines regulate sensitivity of glucose-stimulated insulin secretion in β-cells
Authors: Cooksey Robert C. , Pusuluri Sumitha , Hazel Mark , McClain Donald A.
Published: September 2005

Hexosamines serve a nutrient-sensing function through enzymatic O-glycosylation of proteins. We previously characterized transgenic (Tg) mice with overexpression of the rate-limiting enzyme in hexosamine production, glutamine:fructose-6-phosphate amidotransferase, in β-cells. Animals were hyperinsulinemic, resulting in peripheral insulin resistance. Glucose tolerance deteriorated with age, and males developed diabetes. We therefore examined islet function in these mice by perifusion in vitro. Young (2-mo-old) Tg animals had enhanced sensitivity to glucose of insulin secretion. Insulin secretion was maximal at 20 mM and half maximal at 9.9 ± 0.5 mM glucose in Tg islets compared with maximal at 30 mM and half maximal at 13.5 ± 0.7 mM glucose in wild type (WT; P < 0.005). Young Tg animals secreted more insulin in response to 20 mM glucose (Tg, 1,254 ± 311; WT, 425 ± 231 pg·islet−1·35 min−1; P < 0.01). Islets from older (8-mo-old) Tg mice became desensitized to glucose, with half-maximal secretion at 16.1 ± 0.8 mM glucose, compared with 11.8 ± 0.7 mM in WT ( P < 0.05). Older Tg mice secreted less insulin in response to 20 mM glucose (Tg, 2,256 ± 342; WT, 3,493 ± 367 pg·islet−1·35 min−1; P < 0.05). Secretion in response to carbachol was similar in WT and Tg at both ages. Glucose oxidation was blunted in older Tg islets. At 5 mM glucose, islet CO2production was comparable between Tg and WT. However, WT mice increased islet CO2production 2.7 ± 0.4-fold in 20 mM glucose, compared with only 1.4 ± 0.1-fold in Tg ( P < 0.02). Results demonstrate that hexosamines are involved in nutrient sensing for insulin secretion, acting at least in part by modulating glucose oxidation pathways. Prolonged excess hexosamine flux results in glucose desensitization and mimics glucose toxicity.
Decreased PDH activation and glycogenolysis during exercise following fat adaptation with carbohydrate restoration
Authors: Stellingwerff Trent , Spriet Lawrence L. , Watt Matthew J. , Kimber Nicholas E. , Hargreaves Mark , Hawley John A. , Burke Louise M.
Published: September 2005

Five days of a high-fat diet while training, followed by 1 day of carbohydrate (CHO) restoration, increases rates of whole body fat oxidation and decreases CHO oxidation during aerobic cycling. The mechanisms responsible for these shifts in fuel oxidation are unknown but involve up- and downregulation of key regulatory enzymes in the pathways of skeletal muscle fat and CHO metabolism, respectively. This study measured muscle PDH and HSL activities before and after 20 min of cycling at 70% V̇o2 peakand 1 min of sprinting at 150% peak power output (PPO). Estimations of muscle glycogenolysis were made during the initial minute of exercise at 70% V̇o2 peakand during the 1-min sprint. Seven male cyclists undertook this exercise protocol on two occasions. For 5 days, subjects consumed in random order either a high-CHO (HCHO) diet (10.3 g·kg−1·day−1CHO, or ∼70% of total energy intake) or an isoenergetic high-fat (FAT-adapt) diet (4.6 g·kg−1·day−1FAT, or 67% of total energy) while undertaking supervised aerobic endurance training. On day 6 for both treatments, subjects ingested an HCHO diet and rested before their experimental trials on day 7. This CHO restoration resulted in similar resting glycogen contents (FAT-adapt 873 ± 121 vs. HCHO 868 ± 120 μmol glucosyl units/g dry wt). However, the respiratory exchange ratio was lower during cycling at 70% V̇o2 peakin the FAT-adapt trial, which resulted in an ∼45% increase and an ∼30% decrease in fat and CHO oxidation, respectively. PDH activity was lower at rest and throughout exercise at 70% V̇o2 peak(1.69 ± 0.25 vs. 2.39 ± 0.19 mmol·kg wet wt−1·min−1) and the 1-min sprint in the FAT-adapt vs. the HCHO trial. Estimates of glycogenolysis during the 1st min of exercise at 70% V̇o2 peakand the 1-min sprint were also lower after FAT-adapt (9.1 ± 1.1 vs. 13.4 ± 2.1 and 37.3 ± 5.1 vs. 50.5 ± 2.7 glucosyl units·kg dry wt−1·min−1). HSL activity was ∼20% higher ( P = 0.12) during exercise at 70% V̇o2 peakafter FAT-adapt. Results indicate that previously reported decreases in whole body CHO oxidation and increases in fat oxidation after the FAT-adapt protocol are a function of metabolic changes within skeletal muscle. The metabolic signals responsible for the shift in muscle substrate use during cycling at 70% V̇o2 peakremain unclear, but lower accumulation of free ADP and AMP after the FAT-adapt trial may be responsible for the decreased glycogenolysis and PDH activation during sprinting.
Regulation of HSL serine phosphorylation in skeletal muscle and adipose tissue
Authors: Watt Matthew J. , Holmes Anna G. , Pinnamaneni Srijan K. , Garnham Andrew P. , Steinberg Gregory R. , Kemp Bruce E. , Febbraio Mark A.
Published: September 2005

Hormone-sensitive lipase (HSL) is important for the degradation of triacylglycerol in adipose and muscle tissue, but the tissue-specific regulation of this enzyme is not fully understood. We investigated the effects of adrenergic stimulation and AMPK activation in vitro and in circumstances where AMPK activity and catecholamines are physiologically elevated in humans in vivo (during physical exercise) on HSL activity and phosphorylation at Ser563and Ser660, the PKA regulatory sites, and Ser565, the AMPK regulatory site. In human experiments, skeletal muscle, subcutaneous adipose and venous blood samples were obtained before, at 15 and 90 min during, and 120 min after exercise. Skeletal muscle HSL activity was increased by ∼80% at 15 min compared with rest and returned to resting rates at the cessation of and 120 min after exercise. Consistent with changes in plasma epinephrine, skeletal muscle HSL Ser563and Ser660phosphorylation were increased by 27% at 15 min ( P < 0.05), remained elevated at 90 min, and returned to preexercise values postexercise. Skeletal muscle HSL Ser565phosphorylation and AMPK signaling were increased at 90 min during, and after, exercise. Phosphorylation of adipose tissue HSL paralleled changes in skeletal muscle in vivo, except HSL Ser660was elevated 80% in adipose compared with 35% in skeletal muscle during exercise. Studies in L6 myotubes and 3T3-L1 adipocytes revealed important tissue differences in the regulation of HSL. AMPK inhibited epinephrine-induced HSL activity in L6 myotubes and was associated with reduced HSL Ser660but not Ser563phosphorylation. HSL activity was reduced in L6 myotubes expressing constitutively active AMPK, confirming the inhibitory effects of AMPK on HSL activity. Conversely, in 3T3-L1 adipocytes, AMPK activation after epinephrine stimulation did not prevent HSL activity or glycerol release, which coincided with maintenance of HSL Ser660phosphorylation. Taken together, these data indicate that HSL activity is maintained in the face of AMPK activation as a result of elevated HSL Ser660phosphorylation in adipose tissue but not skeletal muscle.
Occupation of αvβ3-integrin by endogenous ligands modulates IGF-I receptor activation and proliferation of human intestinal smooth muscle
Authors: Kuemmerle John F.
Published: September 2005

We have previously shown that endogenous IGF-I regulates growth of human intestinal smooth muscle cells by stimulating proliferation and inhibiting apoptosis. In active Crohn's disease, expression of IGF-I and the αvβ3-integrin receptor ligands fibronectin and vitronectin is increased. The aim of the present study was to determine whether occupation of the αvβ3-receptor influences IGF-I receptor tyrosine kinase activation and function in human intestinal smooth muscle cells. In untreated cells, IGF-I elicited time-dependent tyrosine phosphorylation of its cognate receptor that was maximal within 2 min and sustained for 30 min. In the presence of the αvβ3-ligand fibronectin, IGF-I-stimulated IGF-I receptor activation was augmented. Conversely, in the presence of the αvβ3-specific disintegrin echistatin, IGF-I-stimulated IGF-I receptor tyrosine kinase phosphorylation was inhibited. IGF-I-stimulated IGF-I receptor activation was accompanied by recruitment of the adapter protein IRS-1, activation of Erk1/2, p70S6 kinase, and proliferation. These effects were augmented by fibronectin and attenuated by echistatin. IGF-I also elicited time-dependent recruitment of protein tyrosine phosphatase SHP-2 that coincided with dephosphorylation of the tyrosine phosphorylated IGF-I receptor tyrosine kinase. The αvβ3-disintegrin echistatin accelerated the rate of SHP-2 recruitment and deactivation of the IGF-I receptor tyrosine kinase. The results show that occupancy of the αvβ3-integrin receptor modulates IGF-I-induced IGF-I receptor activation and function in human intestinal muscle cells. We hypothesize that the concomitant increases in the expression of αvβ3-ligands and of IGF-I in active Crohn's disease may contribute to muscle hyperplasia and stricture formation by acting in concert to augment IGF-I-stimulated IGF-I receptor tyrosine kinase activity and IGF-I-mediated muscle cell growth.
Sympathetic and parasympathetic component of bradycardia triggered by stimulation of NTS P2X receptors
Authors: Kitchen Amy M. , O'Leary Donal S. , Scislo Tadeusz J.
Published: September 2005

We have previously shown that activation of P2X purinoceptors in the subpostremal nucleus tractus solitarius (NTS) produces a rapid bradycardia and hypotension. This bradycardia could occur via sympathetic withdrawal, parasympathetic activation, or a combination of both mechanisms. Thus we investigated the relative roles of parasympathetic activation and sympathetic withdrawal in mediating this bradycardia in chloralose-urethane anesthetized male Sprague-Dawley rats. Microinjections of the selective P2X purinoceptor agonist α,β-methylene ATP (25 pmol/50 nl and 100 pmol/50 nl) were made into the subpostremal NTS in control animals, after atenolol (2 mg/kg iv), a β1-selective antagonist, and after atropine methyl bromide (2 mg/kg iv), a muscarinic receptor antagonist. The bradycardia observed with activation of P2X receptors at the low dose of the agonist is mediated almost entirely by sympathetic withdrawal. After β1-adrenergic blockade, the bradycardia was reduced to just −5.1 ± 0.5 versus −28.8 ± 5.1 beats/min in intact animals. Muscarinic blockade did not produce any significant change in the bradycardic response at the low dose. At the high dose, both β1-adrenergic blockade and muscarinic blockade attenuated the bradycardia similarly, −37.4 ± 6.4 and −40.6 ± 3.7 beats/min, respectively, compared with −88.0 ± 11 beats/min in control animals. Double blockade of both β1-adrenergic and muscarinic receptors virtually abolished the response (−2.5 ± 0.8 beats/min). We conclude that the relative contributions of parasympathetic activation and sympathetic withdrawal are dependent on the extent of P2X receptor activation.
Effect of anti-NGF on ovarian expression of α1- and β2-adrenoceptors, TrkA, p75NTR, and tyrosine hydroxylase in rats with steroid-induced polycystic ovaries
Authors: Manni Luigi , Holmäng Agneta , Cajander Stefan , Lundeberg Thomas , Aloe Luigi , Stener-Victorin Elisabet
Published: September 2005

Estradiol valerate (EV)-induced polycystic ovaries (PCO) in rats are associated with higher ovarian release and content of norepinephrine, decreased β2-adrenoceptors (ARs), and dysregulated expression of α1-AR subtypes, all preceded by an increase in the production of ovarian NGF. The aim of this study was to further elucidate the role of NGF in the ovaries by blocking the action of NGF during development of EV-induced PCO in rats. Control and EV-injected rats were treated with intraperitoneal injections of IgG (control and PCO groups) or with anti-NGF antibodies (anti-NGF and PCO anti-NGF groups) every third day for 5 wk starting from the day of PCO induction. Rat weight, estrous cyclicity, ovarian morphology, ovarian mRNA, and protein expression of α1-AR subtypes, β2-AR, the NGF receptor tyrosine kinase A (TrkA), p75 neurotrophin receptor (p75NTR), and tyrosine hydroxylase (TH) were analyzed. Ovaries in both PCO and PCO anti-NGF groups decreased in size as well as in number and size of corpora lutea. mRNA expression of α1a-AR and TrkA in the ovaries was lower, whereas expression of α1b- and α1d-AR and TH was higher, in the PCO group than in controls. Protein quantities of α1-ARs, TrkA, p75NTR, and TH were higher in the PCO group compared with controls, whereas the protein content of β2-AR was lower. Anti-NGF treatment in the PCO group restored all changes in mRNA and protein content, except that of α1b-AR and TrkA mRNAs, to control levels. The results indicate that the NGF/NGF receptor system plays a role in the pathogenesis of EV-induced PCO in rats.
Modulation by dietary sodium intake of melanocortin 3 receptor mRNA and protein abundance in the rat kidney
Authors: Ni Xi-Ping , Bhargava Aditi , Pearce David , Humphreys Michael H.
Published: September 2005

γ-Melanocyte stimulating hormone (γ-MSH) is a circulating natriuretic peptide hormone derived from proopiomelanocortin (POMC); its concentration in plasma and pituitary POMC mRNA abundance, increase in rats ingesting a high-sodium diet (HSD, 8% NaCl) compared with a low-sodium diet (LSD, 0.07% NaCl). RT-PCR of rat kidney RNA demonstrated reaction products of the expected size in both cortex and medulla for MC3-R, MC4-R, and MC5-R mRNA; no signal for MC1-R or MC2-R was detected. Relative to β-actin or cyclophilin, abundance of the three receptor transcripts after 1 wk of the LSD was approximately equal in both cortex and medulla. After 1 wk of the HSD, mRNA abundance of MC4-R and MC5-R was unchanged, whereas that of MC3-R in medulla more than doubled, the ratio of MC3-R/β-actin signal increasing from 0.38 ± 0.04 on LSD to 0.84 ± 0.04 on HSD ( P < 0.001). No significant increase occurred in the cortex. The increase in MC3-R expression induced by dietary sodium was observed in inner medullary collecting duct (IMCD) cells isolated from the kidneys of HSD rats, suggesting that these cells were the major site of receptor expression in the medulla. Immunoblots of whole medullary and IMCD cell homogenates detected MC3-R immunoreactive protein; its expression was twice as great in samples from HSD vs. LSD rat kidneys, paralleling the increase in MC3-R mRNA abundance on the HSD. No changes in MC4-R or MC5-R protein expression were observed. Incubation of IMCD cell suspensions with increasing concentrations of γ2-MSH led to increased cAMP accumulation, with values from rats on the HSD being roughly double the values from LSD rats. Intrarenal infusion of γ2-MSH (500 fmol/min) increased sodium and cAMP excretion from the infused but not contralateral kidney of HSD rats, while having no effect in LSD rats. These data show that MC3-R is expressed in rat IMCD cells in a manner modulated by dietary sodium intake. Because MC3-R is the receptor with which γ-MSH interacts, our findings suggest the existence of a sodium-regulating system, activated in response to a HSD, which increases urinary sodium excretion to balance the high-sodium intake.
Type 1 neuropeptide Y receptors and α1-adrenoceptors in the neural control of regional renal perfusion
Authors: Eppel Gabriela A. , Luff Susan E. , Denton Kate M. , Evans Roger G.
Published: September 2005

The aim of this study was to determine the contribution of neuropeptide Y (NPY) Y1 receptors in neurally mediated reductions in renal medullary perfusion. In pentobarbital sodium-anesthetized rabbits, electrical stimulation of the renal nerves (RNS, 0.5–16 Hz) decreased renal perfusion in a frequency-dependent manner. Under control conditions, 4 Hz reduced cortical and medullary perfusion by −85 ± 3% and −43 ± 7%, whereas 8 Hz reduced them by −93 ± 2% and −73 ± 4%, respectively. After Y1 receptor antagonism with BIBO3304TF (0.1 mg/kg plus 0.2 mg·kg·−1·h−1), RNS reduced perfusion less (by −65 ± 9% and −12 ± 8% at 4 Hz). α1-Adrenoceptor antagonism with prazosin (0.2 mg/kg plus 0.2 mg kg−1h−1) also inhibited RNS-induced reductions in renal perfusion (−80 ± 4% and −37 ± 10% reductions in the cortex and medulla, respectively, at 8 Hz). When given after BIBO3304TF treatment, prazosin inhibited RNS-induced reductions in cortical and medullary perfusion more profoundly (−57 ± 12% and −25 ± 9% reductions, respectively, at 8 Hz). Y1 receptor- and α1-adrenoceptor-blockade were confirmed by testing vascular responses to renal arterial NPY and phenylephrine boluses. NPY-positive immunolabeling was observed around interlobular arteries, afferent and efferent arterioles, and in the outer medulla. In conclusion, Y1 receptors and α1-adrenoceptors contribute to RNS-induced vasoconstriction in the vessels that control both cortical and medullary perfusion. Consistent with this, NPY immunostaining was associated with blood vessels that control perfusion in both regions. There also seems to be an interaction between Y1 receptors and α1-adrenoceptor-mediated neurotransmission in the control of renal perfusion.
Increased apical targeting of renal ENaC subunits and decreased expression of 11βHSD2 in HgCl2-induced nephrotic syndrome in rats
Authors: Kim Soo Wan , de Seigneux Sophie , Sassen Martin C. , Lee JongUn , Kim Jin , Knepper Mark A. , Frøkiær Jørgen , Nielsen Søren
Published: September 2005

Nephrotic syndrome is often accompanied by sodium retention and generalized edema. We hypothesize that dysregulation of the epithelial sodium channel (ENaC) and/or of sodium (co)transporters may be responsible for the increased sodium retention associated with HgCl2-induced nephropathy. In addition, we examined the hypothesis that the expression of type 2 11β-hydroxysteroid dehydrogenase (11βHSD2) is reduced, contributing to the enhanced mineralocorticoid activity. Membranous nephropathy was induced in Brown Norway rats by repeated injections of HgCl2(1 mg/kg sc), whereas the control group received only vehicle. After 13 days of treatment, the abundance of ENaC subunits, sodium (co)transporters, and 11βHSD2 in the kidney was examined by immunoblotting and immunohistochemistry. HgCl2treatment induced marked proteinuria, hypoalbuminemia, decreased urinary sodium excretion, and ascites. The protein abundance of α-ENaC was increased in the cortex/outer stripe of outer medulla (OSOM) and inner stripe of the outer medulla (ISOM). The protein abundances of β-ENaC and γ-ENaC were decreased in the cortex/OSOM while increased in the ISOM. Immunoperoxidase microscopy demonstrated increased targeting of ENaC subunits to the apical plasma membrane in the distal convoluted tubule, connecting tubule, and cortical and medullary collecting duct segments. Moreover, 11βHSD2 abundance was decreased in cortex/OSOM and ISOM. The protein abundances of type 3 Na/H exchanger (NHE3), Na-K-2Cl cotransporter (NKCC2), and thiazide-sensitive Na-Cl cotransporter (NCC) were decreased. Moreover, the abundance of the α-1 subunit of the Na-K-ATPase was decreased in the cortex/OSOM and ISOM but remained unchanged in the inner medulla. These results suggest that increased apical targeting of ENaC subunits combined with diminished abundance of 11βHSD2 may contribute to sodium retention associated with HgCl2-induced nephrotic syndrome. The decreased abundance of NHE3, NKCC2, NCC, and Na-K-ATPase may play a compensatory role in promoting sodium excretion.
Exogenous 5′-nucleotidase improves glomerular autoregulation in Thy-1 nephritic rats
Authors: Takenaka Tsuneo , Okada Hirokazu , Kanno Yoshihiko , Inoue Tsutomu , Ryuzaki Munekazu , Nakamoto Hidetomo , Kawachi Hiroshi , Shimizu Fujio , Suzuki Hiromichi
Published: September 2005

Experiments were performed to characterize renal hemodynamics in Thy-1 nephritic rats. A monoclonal antibody against Thy-1 was intravenously injected to induce mesangiolysis in rats, and 2 days later renal hemodynamic responses to variations in blood pressure were determined. In the first series of experiments, autoregulation of renal plasma flow (RPF) or glomerular filtration rate (GFR) was impaired in nephritic rats. In response to a reduction in blood pressure (98 ± 2 to 80 ± 1 mmHg), both RPF (4.17 ± 0.63 to 3.20 ± 0.45 ml·min−1·g kidney wt−1, P < 0.05, n = 6) and GFR (0.88 ± 0.05 to 0.75 ± 0.06 ml·min−1·g kidney wt−1, P < 0.05) were decreased in nephritic rats. Intravenous administration of furosemide and 30% albumin, both of which inhibit tubuloglomerular feedback, diminished renal autoregulation in control but not nephritic rats. In the second studies, the infusion of 5′-nucleotidase, an enzyme expressed on mesangial cells, into a renal artery ameliorated the magnitude of autoregulatory decrements in GFR in nephritic rats (−16 ± 5 to −6 ± 2%, P < 0.05, n = 6), but this enzyme failed to alter renal autoregulation in control rats. In the third studies, the effects of indomethacin were examined in nephritic rats. Inhibition of prostaglandin synthesis reduced RPF (4.07 ± 0.30 to 1.54 ± 0.22 ml·min−1·g kidney wt−1, P < 0.05, n = 5) and GFR (1.03 ± 0.18 to 0.69 ± 0.13 ml·min−1·g kidney wt−1, P < 0.05) in nephritic rats. However, cyclooxygenase inhibition failed to restore renal autoregulation in nephritic rats. Our results indicate that renal autoregulation is impaired in Thy-1 nephritis. Furthermore, the present data provide evidence that prostanoids contribute to maintain renal circulation in nephritic rats. Finally, our findings suggest that mesangial cells and/or 5′-nucleotidase plays an important role in mediating renal autoregulation.
Vasopressin-2-receptor antagonism augments water excretion without changes in renal hemodynamics or sodium and potassium excretion in human heart failure
Authors: Costello-Boerrigter Lisa C. , Smith William B. , Boerrigter Guido , Ouyang John , Zimmer Christopher A. , Orlandi Cesare , Burnett John C.
Published: September 2005

Diuretics are frequently required to treat fluid retention in patients with congestive heart failure (CHF). Unfortunately, they can lead to a decline in renal function, electrolyte depletion, and neurohumoral activation. Arginine vasopressin (AVP) promotes renal water reabsorption via the V2 receptor, and its levels are increased in CHF. This study was designed to assess the effects of a single oral dose of tolvaptan, a selective V2-receptor blocker, in the absence of other medications, on renal function in human CHF and to compare this to the effects of a single oral dose of furosemide. We hypothesized that V2-receptor antagonism would yield a diuresis comparable to furosemide but would not adversely affect renal hemodynamics, plasma electrolyte concentration, or neurohumoral activation in stable human CHF. Renal and neurohumoral effects of tolvaptan and furosemide were assessed in an open-label, randomized, placebo-controlled crossover study in 14 patients with NYHA II-III CHF. Patients received placebo or 30 mg of tolvaptan on day 1 and were crossed over to the other medication on day 3. On day 5, all subjects received 80 mg of furosemide. Tolvaptan and furosemide induced similar diuretic responses. Unlike tolvaptan, furosemide increased urinary sodium and potassium excretion and decreased renal blood flow. Tolvaptan, furosemide, and placebo did not differ with respect to mean arterial pressure, glomerular filtration rate, or serum sodium and potassium. We conclude that tolvaptan is an effective aquaretic with no adverse effects on renal hemodynamics or serum electrolytes in patients with mild to moderate heart failure.
Lower antioxidant capacity and elevated p53 and p21 may be a link between gender disparity in renal telomere shortening, albuminuria, and longevity
Authors: Tarry-Adkins Jane L. , Ozanne Susan E. , Norden Anthony , Cherif Hanane , Hales C. Nicholas
Published: September 2005

It is well documented that females live longer than males and more renal damage occurs in males. However, the underlying mechanisms are not fully understood. The aim of this study was to define aging effects on albuminuria and kidney telomere length from male and female rats and to determine mechanisms, which may explain any observed differences. Cellular senescence is known to play a major role in nephropathology, and as such, a range of senescence markers were compared in male and female renal tissue. Oxidative stress has been shown to accelerate telomere shortening and elicit cellular growth arrest. Thus major antioxidants, MnSOD, glutathione peroxidase I, and glutathione reductase, were also evaluated. Urinary albumin excretion increased with age in both sexes, but the increase was greater in males than females. In the cortex and medulla of both male and female rats, age-related telomere shortening occurred, the effect being more pronounced in males than in females. The cortical region had more short telomeres than the medulla in both genders. p53 And p21 expression over time significantly increased in males, but not in females. MnSOD expression was elevated in female vs. male cortex. Gxp1 and glutathione reductase levels were increased in the older female cortex compared with males. Our findings indicate that a reduction in oxidative damage protection may be responsible for accelerated telomere shortening over time, resulting in increased cellular senescence, loss of renal function, and death in male rats.
Expression and function of COX isoforms in renal medulla: evidence for regulation of salt sensitivity and blood pressure
Authors: Ye Wenling , Zhang Hui , Hillas Elaine , Kohan Donald E. , Miller R. Lance , Nelson Raoul D. , Honeggar Matthew , Yang Tianxin
Published: September 2005

Expression of cyclooxygenase (COX)-2, but not COX-1, in the renal medulla is stimulated by chronic salt loading; yet the functional implication of this phenomenon is incompletely understood. The present study examined the cellular localization and antihypertensive function of high-salt-induced COX-2 expression in the renal medulla, with a parallel assessment of the function of COX-1. COX-2 protein expression in response to high-salt loading, assessed by immunostaining, was found predominantly in inner medullary interstitial cells, whereas COX-1 protein was abundant in collecting duct (CD) and inner medullary interstitial cells and was not affected by high salt. We compared mRNA expressions of COX-1 and COX-2 in CD vs. non-CD cells isolated from aquaporin 2-green fluorescent protein transgenic mice. A low level of COX-2 mRNA, but a high level of COX-1 mRNA, as determined by real-time RT-PCR, was detected in CD compared with non-CD segments. During high-salt intake, chronic infusions of the COX-2 blocker NS-398 and the COX-1 blocker SC-560 into the renal medulla of Sprague-Dawley rats for 5 days induced ∼30- and 15-mmHg increases in mean arterial pressure, respectively. During similar high-salt intake, COX-1 knockout mice exhibited a gradual, but significant, increase in systolic blood pressure that was associated with a marked suppression of urinary PGE2excretion. Therefore, we conclude that the two COX isoforms in the renal medulla play a similar role in the stabilization of arterial blood pressure during salt loading.
Functional expression of the renin-angiotensin system in human podocytes
Authors: Liebau Max C. , Lang D. , Böhm J. , Endlich N. , Bek Martin J. , Witherden Ian , Mathieson Peter W. , Saleem Moin A. , Pavenstädt Hermann , Fischer Karl-Georg
Published: September 2005

Experimental and clinical studies impressively demonstrate that angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) significantly reduce proteinuria and retard progression of glomerular disease. The underlying intraglomerular mechanisms are not yet fully elucidated. As podocyte injury constitutes a critical step in the pathogenesis of glomerular proteinuria, beneficial effects of ACEI and ARB may partially result from interference with a local renin-angiotensin system (RAS) in podocytes. The knowledge of expression and function of a local RAS in podocytes is limited. In this study, we demonstrate functional expression of key components of the RAS in differentiated human podocytes: podocytes express mRNA for angiotensinogen, renin, ACE type 1, and the AT1and AT2angiotensin receptor subtypes. In Western blot experiments and immunostainings, expression of the AT1and AT2receptor was demonstrated both in differentiated human podocytes and in human kidney cortex. ANG II induced a concentration-dependent increase in cytosolic Ca2+concentration via AT1receptors in differentiated human podocytes, whereas it did not increase cAMP. Furthermore, ANG II secretion was detected, which was blocked by neither the ACEI captopril nor the renin inhibitor remikiren nor the chymase inhibitor chymostatin. ANG II secretion of podocytes was not increased by mechanical stress. Finally, ANG II was found to increase staurosporine-induced apoptosis in podocytes. We speculate that ACEI and ARB exert their beneficial effects, in part, by interfering with a local RAS in podocytes. Further experiments are required to identify the underlying molecular mechanism(s) of podocyte protection.
Assessment of left ventricular diastolic function by early diastolic mitral annulus peak acceleration rate: experimental studies and clinical application
Authors: Ruan Qinyun , Rao Liyun , Middleton Katherine J. , Khoury Dirar S. , Nagueh Sherif F.
Published: September 2005

We sought to examine the hemodynamic determinants and clinical application of the peak acceleration rate of early (Ea) diastolic velocity of the mitral annulus by tissue Doppler. Simultaneous left atrial and left ventricular (LV) catheterization and Doppler echocardiography were performed in 10 dogs. Preload was altered using volume infusion and caval occlusion, whereas myocardial lusitropic state was altered with dobutamine and esmolol. The clinical application was examined in 190 consecutive patients (55 control, 41 impaired relaxation, 46 pseudonormal, and 48 restrictive LV filling). In addition, in 60 consecutive patients, we examined the relation between it and mean wedge pressure with simultaneous Doppler echocardiography and right heart catheterization. In canine studies, a significant positive relation was present between peak acceleration rate of Ea and transmitral pressure gradient only in the stages with normal or enhanced LV relaxation, but with no relation in the stages where the time constant of LV relaxation (τ) was ≥50 ms. Its hemodynamic determinants were τ, LV minimal pressure, and transmitral pressure gradient. In clinical studies, peak acceleration rate of Ea was significantly lower in patients with impaired LV relaxation irrespective of filling pressures ( P < 0.001) and with similar accuracy to peak Ea velocity (area under the curve for septal and lateral peak acceleration rates: both 0.78) in identifying these patients. No significant relation was observed between peak acceleration rate and mean wedge pressure. Peak acceleration rate of Ea appears to be a useful index of LV relaxation but not of filling pressures and can be applied to identify patients with impaired LV relaxation irrespective of their filling pressures.
Direct method for variational problems via hybrid of block‐pulse and chebyshev functions
Authors: Razzaghi Mohsen , Marzban Hamid-Reza
Published: September 2005

A direct method for finding the solution of variational problems using a hybrid function is discussed. The hybrid functions which consist of block‐pulse functions plus Chebyshev polynomials are introduced. An operational matrix of integration and the integration of the cross product of two hybrid function vectors are presented and are utilized to reduce a variational problem to the solution of an algebraic equation. Illustrative examples are included to demonstrate the validity and applicability of the technique.
State‐feedback control of LPV sampled‐data systems
Authors: Tan K. , Grigoriadis K. M.
Published: September 2005

In this paper, we address the analysis and the state‐feedback synthesis problems for linear parameter‐varying (LPV) sampled‐data control systems. We assume that the state‐space data of the plant and the sampling interval depend on parameters that are measurable in real‐time and vary in a compact set with bounded variation rates. We explore criteria such as the stability, the energy‐to‐energy gain (induced L2 norm) and the energy‐to‐peak gain (induced L2 ‐to‐ L∞ norm) of such sampled‐data LPV systems using parameter‐dependent Lyapunov functions. Based on these analysis results, the sampled‐data state‐feedback control synthesis problems are examined. Both analysis and synthesis conditions are formulated in terms of linear matrix inequalities that can be solved via efficient interior‐point algorithms.