bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Culture and a Novel 5′
Taq
Nuclease Assay for Direct Detection of
Campylobacter fetus
subsp.
venerealis
in Clinical Specimens from Cattle
Authors: McMillen Lyle , Fordyce Geoffry , Doogan Vivienne J. , Lew Ala E.
Published: March 2006

A
Campylobacter fetus
subsp.
venerealis
-specific 5′
Taq
nuclease PCR assay using a 3′ minor groove binder-DNA probe (TaqMan MGB) was developed based on a subspecies-specific fragment of unknown identity (S. Hum, K. Quinn, J. Brunner, and S. L. On, Aust. Vet. J. 75:827-831, 1997). The assay specifically detected four
C. fetus
subsp.
venerealis
strains with no observed cross-reaction with
C. fetus
subsp.
fetus
-related
Campylobacter
species or other bovine venereal microflora. The 5′
Taq
nuclease assay detected approximately one single cell compared to 100 and 10 cells in the conventional PCR assay and 2,500 and 25,000 cells from selective culture from inoculated smegma and mucus, respectively. The respective detection limits following the enrichments from smegma and mucus were 5,000 and 50 cells/inoculum for the conventional PCR compared to 500 and 50 cells/inoculum for the 5′
Taq
nuclease assay. Field sampling confirmed the sensitivity and the specificity of the 5′
Taq
nuclease assay by detecting an additional 40 bulls that were not detected by culture. Urine-inoculated samples demonstrated comparable detection of
C. fetus
subsp.
venerealis
by both culture and the 5′
Taq
nuclease assay; however, urine was found to be less effective than smegma for bull sampling. Three infected bulls were tested repetitively to compare sampling tools, and the bull rasper proved to be the most suitable, as evidenced by the improved ease of specimen collection and the consistent detection of higher levels of
C. fetus
subsp.
venerealis
. The 5′
Taq
nuclease assay demonstrates a statistically significant association with culture (χ
2
= 29.8;
P
< 0.001) and significant improvements for the detection of
C. fetus
subsp.
venerealis
-infected animals from crude clinical extracts following prolonged transport.
Acute hepatitis B in the era of immunisation: pitfalls in the identification of high risk patients
Authors: Rosner G , Lurie Y , Blendis L , Halpern Z , Oren R
Published: March 2006

Background

Since the adoption of a universal hepatitis B immunisation strategy, the reported incidence of acute hepatitis B has declined dramatically worldwide including in Israel. However, new cases of acute hepatitis B still occur. The aim of this study was to describe the incidence of acute hepatitis B in a referral area, routes of transmission, and outcome.

Methods

The charts of all new hepatitis B patients, who visited the clinic in the years 2002 and 2003 (January 2002 to December 2003), were reviewed. The main criteria for a diagnosis of acute hepatitis B were transient increase of alanine transaminase activity, and hepatitis B surface antigen seroconversion.

Results

Twenty nine men and seven women were diagnosed with acute hepatitis B infection during the study period. Two patients were previously vaccinated with hepatitis B vaccine. One case of hepatitis D coinfection was reported. The incidence of acute hepatitis B in the referral area was estimated as 2.25 per 100 000 adult population. Mean age was 36 years (17–75). Twenty one patients (18 men and 3 women) acquired the virus through unprotected sexual contact, and seven patients through iatrogenic exposure. Thirty three patients underwent spontaneous seroconversion while three patients became chronic carriers.

Conclusions

Despite a universal immunisation policy, frequent cases of acute hepatitis B in Israel are still seen. High risk heterosexual activity and iatrogenic exposure seem to be the commonest routes of transmission. Further recommendations regarding vaccination policy are discussed.
Ageing and the auditory system
Authors: Howarth A , Shone G R
Published: March 2006

There are a number of pathophysiological processes underlying age related changes in the auditory system. The effects of hearing loss can have consequences beyond the immediate loss of hearing, and may have profound effects on the functioning of the person. While a deficit in hearing can be corrected to some degree by a hearing aid, auditory rehabilitation requires much more than simply amplifying external sound. It is important that those dealing with elderly people are aware of all the issues involved in age related hearing loss.
Is non-steroidal anti-inflammaory drug (NSAID) enteropathy clinically more important than NSAID gastropathy?
Authors: Adebayo D , Bjarnason I
Published: March 2006

The side effects of conventional non-steroidal anti-inflammatory drugs (NSAIDs) on the stomach is undoubtedly a serious public health problem contributing significantly to the morbidity and mortality of patients receiving these drugs. However, the damage of NSAIDs is not confined to the stomach. Indeed the short term and long term damage of NSAIDs on the small bowel (NSAID enteropathy) is more frequent than NSAID gastropathy. Furthermore, NSAID enteropathy is associated with complications (bleeding and protein loss). While many of these are mild, the serious events (significant bleeding, perforation, obstruction, and sudden death) are frequent as that reported for NSAID gastropathy. The diagnosis of NSAID enteropathy has been greatly aided by the introduction of wireless capsule enteroscopy.
ON THE NOTION OF CONDITIONAL SYMMETRY OF DIFFERENTIAL EQUATIONS
Authors: CICOGNA GIAMPAOLO , LAINO MICHELE
Published: March 2006

Symmetry properties of PDE's are considered within a systematic and unifying scheme: particular attention is devoted to the notion of conditional symmetry, leading to the distinction and a precise characterization of the notions of "true" and "weak" conditional symmetry. Their relationship with exact and partial symmetries is also discussed. An extensive use of "symmetry-adapted" variables is made; several clarifying examples, including the case of Boussinesq equation, are also provided.
INTEGRATED WIDE-BAND CMOS DUOBINARY TRANSMITTER FOR OPTICAL COMMUNICATION SYSTEMS
Authors: TAO RUI , BERROTH MANFRED
Published: March 2006

Inter symbol interference (ISI) caused by dispersion in optical fibers is the major limiting factor on the achievable data rate or transmission distance in high-speed fiber-optic interconnects1. Compared with optical-domain and other electrical-domain dispersion compensation methods, duobinary coding technology is used due to its higher spectral efficiency. In this paper, a monolithically integrated duobinary optical transmitter has be designed and fabricated in standard 0.18 μm CMOS technology. This transmitter consists of a duobinary encoder and a VCSEL driver. The master-slave D flip-flop structure is used to generate the wideband one bit delay which is important for the realization of duobinary signal. An open drain structure is used in VCSEL driver design to provide the higher current output in low supply voltage condition. This duobinary transmitter can operate up to 5 Gb/s with 20 mA current output. The current consumption is only 50 mA under 1.8 V supply voltage.
CHAOTIFICATION OF DISCRETE SYSTEMS BASED ON MODELS IDENTIFIED FROM DATA
Authors: AGUIRRE LUIS ANTONIO
Published: March 2006

This work discusses the chaotification of nonchaotic discrete systems based on a procedure that requires the jacobian matrix of the uncontrolled dynamics. The aim is to verify if chaotification is still effective when the jacobian is analytically obtained from identified models (data-driven models) rather than assumed known. This study, that includes two numerical examples, shows that chaotification can be achieved using nonlinear models. Several other issues concerning modeling and the control effort required for chaotification are briefly discussed.
A HYBRID IMPULSIVE AND SWITCHING CONTROL STRATEGY FOR SYNCHRONIZATION OF NONLINEAR SYSTEMS AND APPLICATION TO CHUA'S CHAOTIC CIRCUIT
Authors: GUAN ZHI-HONG , HILL DAVID J. , YAO JING
Published: March 2006

In this paper, a new hybrid impulsive and switching control strategy for synchronization of nonlinear systems is developed. Using switched Lyapunov functions, several new criteria for global exponential stability of hybrid impulsive and switching nonlinear systems are established and, particularly, some simple sufficient conditions for driving the synchronization error to zero exponentially are proposed. As an application, Chua's chaotic circuit is investigated.
NON-STATISTICAL FLUCTUATIONS IN THE ANGULAR DISTRIBUTION OF TARGET-ASSOCIATED PROTONS EMITTED IN 28Si-AgBr COLLISIONS AT 14.6 AGeV
Authors: HAQ M. MOHIB-UL , ISLAM SAIFUL , HASAN R.
Published: March 2006

This paper presents an analysis of medium energy target-associated protons emitted in 28 Si-AgBr collisions at 14.6 AGeV. Evidence of non-statistical fluctuations and multifractality in the data has been found. Values of the multifractal specific heat for our data have also been determined.
THE EFFECTS OF DEFORMATION AND PAIRING CORRELATIONS ON NUCLEAR CHARGE FORM FACTOR
Authors: MOUSTAKIDIS CH. C. , KOSMAS T. S. , ŠIMKOVIC F. , FAESSLER AMAND
Published: March 2006

A set of moderately deformed s–d shell nuclei is employed for testing the reliability of the nuclear ground state wave functions which are obtained in the context of a BCS approach and offer a simultaneous consideration of deformation and pairing correlations effects. In this method, the mean field is assumed to be an axially symmetric Woods-Saxon potential and the effective two-body interaction is a monopole pairing force. As quantities of main interest we have chosen the nuclear form factors, the occupancies of the active (surface) orbits and the Fermi sea depletion, which provide quite good tests for microscopic descriptions of nuclei within many body theories. For our comparisons with results emerging from other similar methods, an axially deformed harmonic oscillator field is also utilized.
REACTIVE RESONANCE AND FORMATION MECHANISM STUDIES OF THE H + NO → N + OH OR O + NH REACTION
Authors: WANG QIANG , CAI ZHENGTING , FENG DACHENG
Published: March 2006

The partial potential energy surface (PPES) of H + NO → N + OH or O + NH of 3A″ symmetry is first constructed using QCISD (T) method with 6-311++g** basis set, and then we speculate the existence of the scattering resonance states of these reactions. Finally, we estimate that the lifetime of scattering resonance state is about 1.5 ps, which is in agreement with Schatz's conclusion (~1.2 ps ). The scattering resonance states of the two reactions belong to the Feshbach type. The results are consistent with the probabilities calculations reported in the literatures.
ANAB INITIOSTUDY OF PROTON-TRANSFER REACTION INBe2+(H2O)nAND THE SPATIAL CHANGING FEATURE IN THE FORMATION PROCESS OF HYDROXIDE
Authors: LI XIN , YANG ZHONG-ZHI
Published: March 2006

The proton-transfer reaction in Be2+( H2O )nis investigated by an ab initio calculation. With an increasing number of water molecules, there are different formation processes of hydroxide, and the reaction barrier is dependent on the cluster size n. By MELD ab initio program and own-coding programs, we have calculated the potential acting on an electron within a molecule, and have investigated the changing of spatial appearance for the formation process of hydroxide, by the molecular intrinsic characteristic contour defined in terms of the classical turning point of electron movement.
A Knowledge-Based Framework to Manage Flexibility in ERP Systems
Authors: Palanisamy Ramaraj
Published: March 2006

The need for flexibility in organisations and information systems has long been recognised. Much research has been conducted to understand the flexibility concept in various types of information systems. Comparatively less research has been conducted to understand the process of managing flexibility in enterprise resource planning (ERP) systems. This paper focuses on developing a conceptual framework for managing flexibility in ERP systems emphasising the need for a match between external and internal flexibilities. The application of the framework is illustrated with a case example. The framework is intended to understand ERP systems' flexibility enabled organisational performance. The framework will provide a basis to assess the impact of ERP systems' flexibility on organisations, to measure the internal and external flexibilities of ERP systems and to develop guidelines to manage flexibilities for ERP systems.
Sulfide-detoxifying enzymes in the human colon are decreased in cancer and upregulated in differentiation
Authors: Ramasamy S. , Singh S. , Taniere P. , Langman M. J. S. , Eggo M. C.
Published: February 2006

H2S is highly toxic and selectively inhibits butyrate oxidation in colonocytes. Ineffective detoxification may result in mucosal insult, inflammation, and ultimately in colorectal cancer (CRC). Rhodanese can detoxify H2S and is comprised of two isoenzymes: thiosulfate sulfurtransferase (TST) and mercaptopyruvate sulfurtransferase (MST). Using specific antisera to discriminate TST from MST, we found that only TST could detoxify H2S. In sections of normal colon, both enzymes were located on the luminal mucosal surface, and they were expressed in the colonocytes but not in the mucin-secreting goblet cells. Expression of both enzymes was focally lost in ulcerative colitis and markedly reduced in advanced colon cancer, the disease progression correlating with the decreased expression of MST and TST. In HT-29 cells, a human colon cancer cell line, TST activity and expression were significantly increased by butyrate and by histone deacetylase inhibition, agents that promote HT-29 cell differentiation. Sulfide (0.1 mM) also increased TST activity, but higher sulfide concentrations (0.3–3 mM) were toxic. Preincubation in butyrate to increase TST expression, decreased sensitivity of the cells to sulfide toxicity. We conclude that decreased expression of TST (or MST) is a tumor marker for CRC. TST expression is increased in colonocyte differentiation. Dysregulation of TST expression and activity resulting in inability to effectively detoxify could be a factor in the cell loss and inflammation that accompany ulcerative colitis and ultimately then in CRC.
Shear stress induces hepatocytePAI-1gene expression through cooperative Sp1/Ets-1 activation of transcription
Authors: Nakatsuka Hideki , Sokabe Takaaki , Yamamoto Kimiko , Sato Yoshinobu , Hatakeyama Katsuyoshi , Kamiya Akira , Ando Joji
Published: February 2006

Partial hepatectomy causes hemodynamic changes that increase portal blood flow in the remaining lobe, where the expression of immediate-early genes, including plasminogen activator inhibitor-1 (PAI-1), is induced. We hypothesized that a hyperdynamic circulatory state occurring in the remaining lobe induces immediate-early gene expression. In this study, we investigated whether the mechanical force generated by flowing blood, shear stress, induces PAI-1 expression in hepatocytes. When cultured rat hepatocytes were exposed to flow, PAI-1 mRNA levels began to increase within 3 h, peaked at levels significantly higher than the static control levels, and then gradually decreased. The flow-induced PAI-1 expression was shear stress dependent rather than shear rate dependent and accompanied by increased hepatocyte production of PAI-1 protein. Shear stress increased PAI-1 transcription but did not affect PAI-1 mRNA stability. Functional analysis of the 2.1-kb PAI-1 5′-promoter indicated that a 278-bp segment containing transcription factor Sp1 and Ets-1 consensus sequences was critical to the shear stress-dependent increase of PAI-1 transcription. Mutations of both the Sp1 and Ets-1 consensus sequences, but not of either one alone, markedly prevented basal PAI-1 transcription and abolished the response of the PAI-1 promoter to shear stress. EMSA and chromatin immunoprecipitation assays showed binding of Sp1 and Ets-1 to each consensus sequence under static conditions, which increased in response to shear stress. In conclusion, hepatocyte PAI-1 expression is flow sensitive and transcriptionally regulated by shear stress via cooperative interactions between Sp1 and Ets-1.
Increased levels of mucins in the cystic fibrosis mouse small intestine, and modulator effects of the Muc1 mucin expression
Authors: Malmberg Emily K. , Noaksson Karin A. , Phillipson Mia , Johansson Malin E. V. , Hinojosa-Kurtzberg Marina , Holm Lena , Gendler Sandra J. , Hansson Gunnar C.
Published: February 2006

The mouse model (Cftrtm1UNC/Cftrtm1UNC) for cystic fibrosis (CF) shows mucus accumulation and increased Muc1 mucin mRNA levels due to altered splicing (Hinojosa-Kurtzberg AM, Johansson MEV, Madsen CS, Hansson GC, and Gendler SJ. Am J Physiol Gastrointest Liver Physiol 284: G853–G862, 2003). However, it is not known whether Muc1 is a major mucin contributing to the increased mucus and why CF/Muc1−/− mice show lower mucus accumulation. To address this, we have purified mucins from the small intestine of CF mice using guanidinium chloride extraction, ultracentrifugation, and gel filtration and analyzed them by slot blot, gel electrophoresis, proteomics, and immunoblotting. Normal and CF mice with wild-type (WT) Muc1 or Muc1−/− or that are transgenic for human MUC1 (MUC1.Tg, on a Muc1−/− background) were analyzed. The total amount of mucins, both soluble and insoluble in guanidinium chloride, increased up to 10-fold in the CF mice compared with non-CF animals, whereas the CF mice lacking Muc1 showed intermediate levels between the CF and non-CF mice. However, the levels of Muc3 (orthologue of human MUC17) were increased in the CF/Muc1−/− mice compared with the CF/MUC1.Tg animals. The amount of MUC1 mucin was increased several magnitudes in the CF mice, but MUC1 did still not appear to be a major mucin. The amount of insoluble mucus of the large intestine was also increased in the CF mice, an effect that was partially restored in the CF/Muc1−/− mice. The thickness of the firmly adherent mucus layer of colon in the Muc1−/− mice was significantly lower than that of WT mice. The results suggest that MUC1 is not a major component in the accumulated mucus of CF mice and that MUC1 can influence the amount of other mucins in a still unknown way.
Convergence of sensory pathways in the development of somatic and visceral hypersensitivity
Authors: Bielefeldt Klaus , Lamb Kenneth , Gebhart G. F.
Published: February 2006

Sensory neurons innervating different tissues converge onto second-order neurons in the spinal cord. We examined whether inflammation or transient overexpression of nerve growth factor (NGF) in one tissue triggers hypersensitivity in referral sites. Thresholds to mechanical and thermal stimulation of the hindpaw, visceromotor responses to colorectal distension, and cystometrograms were performed in appropriate controls and mice with experimentally induced cystitis, inflammation of the hindpaw or front paw, or injection of viral vectors encoding NGF or green fluorescent protein (GFP). Cystitis and NGF but not GFP overexpression in the bladder triggered bladder hyperactivity associated with mechanical and thermal hypersensitivity in cutaneous referral sites and enhanced responses to colorectal distension. Hindpaw inflammation and injection of the NGF- but not GFP-encoding viral vector or front paw inflammation induced mechanical and thermal hyperalgesia in the affected hindpaw and increased responses to colorectal distension without altering the micturition reflex. In conclusion, sensitization of sensory pathways by inflammation or NGF contributes to the development of hypersensitivity in neighboring organs and cutaneous referral sites and provides a potential mechanism underlying the coexistence of pain syndromes in patients with functional diseases.
Cardiac parasympathetic regulation: respective associations with cardiorespiratory fitness and training load
Authors: Buchheit Martin , Gindre Cyrille
Published: February 2006

The objective of this study was to establish the separate associations between parasympathetic modulations of the heart [evaluated through heart rate (HR) variability (HRV) indexes and postexercise HR recovery (HRR) indexes] with cardiorespiratory fitness and training load. We have measured cardiorespiratory fitness through peak oxygen consumption (V̇o2 max) and estimated weekly training load with the Baecke sport score in 55 middle-aged individuals (30.8 ± 1.8 yr, body mass index 24.5 ± 0.4 kg/m2). HRV indexes were analyzed at rest under controlled breathing, and HRR was estimated from HR curve fitting after maximal exercise or from measurements of the number of beats recovered at 60 s after exercise. Multiple linear regressions were used to investigate the separate relationships between vagal-related HRV indexes and V̇o2 max and Baecke scores. On the basis of their V̇o2 max and Baecke scores, subjects were classified as fit or unfit and as low trained (LT) or moderately trained (MT), which yielded four groups: UnfitLT, UnfitMT, FitLT, and FitMT. Vagal-related HRV indexes were positively correlated with V̇o2 max ( P < 0.05) but not with Baecke scores. In contrast, HRR indexes were related to Baecke scores ( P < 0.05) but not with V̇o2 max. FitLT and FitMT had significantly higher ( P < 0.05) normalized vagal-related HRV indexes than UnfitLT and UnfitMT, but HRR did not change. Moderate training was associated with significantly lower HRR indexes both in UnfitMT and FitMT compared with UnfitLT and FitLT, but there was no difference in vagal-related HRV indexes. These results indicate that vagal-related HRV indexes are related more to cardiorespiratory fitness, whereas HRR appears to be better associated with training load.
A β1-adrenergic receptor CaM kinase II-dependent pathway mediates cardiac myocyte fetal gene induction
Authors: Sucharov Carmen C. , Mariner Peter D. , Nunley Karin R. , Long Carlin , Leinwand Leslie , Bristow Michael R.
Published: February 2006

β-Adrenergic signaling plays an important role in the natural history of dilated cardiomyopathies. Chronic activation of β-adrenergic receptors (β1-AR and β2-AR) during periods of cardiac stress ultimately harms the failing heart by mechanisms that include alterations in gene expression. Here, we show that stimulation of β-ARs with isoproterenol in neonate rat ventricular myocytes causes a “fetal” response in the relative activities of the human cardiac fetal and/or adult gene promoters that includes repression of the human and rat α-myosin heavy chain (α-MyHC) promoters with simultaneous activation of the human atrial natriuretic peptide (ANP) and rat β-MyHC promoters. We also show that the promoter changes correlate with changes in endogenous gene expression as measured by mRNA expression. Furthermore, we show that these changes are specifically mediated by the β1-AR, but not the β2-AR, and are independent of α1-AR stimulation. We also demonstrate that the fetal gene response is independent of cAMP and protein kinase A, whereas inhibition of Ca2+/calmodulin-dependent protein kinase (CaMK) pathway blocks isoproterenol-mediated fetal gene program induction. Finally, we show that induction of the fetal program is dependent on activation of the L-type Ca2+channel. We conclude that in neonatal rat cardiac myocytes, agonist-occupied β1-AR mobilizes Ca2+stores to activate fetal gene induction through cAMP independent pathways that involve CaMK.
Heart rate response to onset of exercise: evidence for enhanced cardiac sympathetic activity in animals susceptible to ventricular fibrillation
Authors: Billman George E.
Published: February 2006

A large heart rate (HR) increase at the onset of exercise has been linked to an increased risk for adverse cardiovascular events, including cardiac death. However, the relationship between changes in cardiac autonomic regulation induced by exercise onset and the confirmed susceptibility to ventricular fibrillation (VF) has not been established. Therefore, a retrospective analysis of the HR response to exercise onset was made in mongrel dogs with healed myocardial infarctions that were either susceptible (S, n = 131) or resistant (R, n = 114) to VF (induced by a 2-min occlusion of the left circumflex artery during the last minute of exercise). The ECG was recorded, and time series analysis of HR variability (vagal activity index, the 0.24–1.04-Hz frequency component of R-R interval variability) was measured before and 30, 60, and 120 s after the onset of exercise (treadmill running). Exercise elicited significantly (ANOVA, P < 0.0001) greater increases in HR in susceptible dogs at all three times (e.g., at 60 s: R, 46.8 ± 2.3 vs. S, 57.1 ± 2.2 beats/min). However, the vagal activity index decreased to a similar extent in both groups of dogs (at 60 s: R, −2.8 ± 0.1 vs. S, −3.0 ± 0.2 ln ms2). β-Adrenoceptor blockade (BB, propranolol 1.0 mg/kg iv) reduced the HR increase and eliminated the differences noted between the groups [at 60 s: R ( n = 26), 40.4 ± 3.2 vs. S ( n = 31), 37.5 ± 2.4 beats/min]. After BB, exercise once again elicited similar declines in vagal activity in both groups (at 60 s: R, −3.6 ± 0.5 vs. S, −3.2 ± 0.4 ln ms2). When considered together, these data suggest that at the onset of exercise HR increases to a greater extent in animals prone to VF compared with dogs resistant to this malignant arrhythmia due to an enhanced cardiac sympathetic activation in the susceptible dogs.
Consequences of cardiac myocyte-specific ablation of KATPchannels in transgenic mice expressing dominant negative Kir6 subunits
Authors: Tong XiaoYong , Porter Lisa M. , Liu GongXin , Dhar-Chowdhury Piyali , Srivastava Shekhar , Pountney David J. , Yoshida Hidetada , Artman Michael , Fishman Glenn I. , Yu Cindy , Iyer Ramesh , Morley Gregory E. , Gutstein David E. , Coetzee William A.
Published: February 2006

Cardiac ATP-sensitive K+(KATP) channels are formed by Kir6.2 and SUR2A subunits. We produced transgenic mice that express dominant negative Kir6.x pore-forming subunits (Kir6.1-AAA or Kir6.2-AAA) in cardiac myocytes by driving their expression with the α-myosin heavy chain promoter. Weight gain and development after birth of these mice were similar to nontransgenic mice, but an increased mortality was noted after the age of 4–5 mo. Transgenic mice lacked cardiac KATPchannel activity as assessed with patch clamp techniques. Consistent with a decreased current density observed at positive voltages, the action potential duration was increased in these mice. Some myocytes developed EADs after isoproterenol treatment. Hemodynamic measurements revealed no significant effects on ventricular function (apart from a slightly elevated heart rate), whereas in vivo electrophysiological recordings revealed a prolonged ventricular effective refractory period in transgenic mice. The transgenic mice tolerated stress less well as evident from treadmill stress tests. The proarrhythmogenic features and lack of adaptation to a stress response in transgenic mice suggest that these features are intrinsic to the myocardium and that KATPchannels in the myocardium have an important role in protecting the heart from lethal arrhythmias and adaptation to stress situations.
The ubiquitin-proteasome system in cardiac physiology and pathology
Authors: Powell Saul R.
Published: February 2006

The ubiquitin-proteasome system (UPS) is the major nonlysosomal pathway for intracellular protein degradation, generally requiring a covalent linkage of one or more chains of polyubiquitins to the protein intended for degradation. It has become clear that the UPS plays major roles in regulating many cellular processes, including the cell cycle, immune responses, apoptosis, cell signaling, and protein turnover under normal and pathological conditions, as well as in protein quality control by removal of damaged, oxidized, and/or misfolded proteins. This review will present an overview of the structure, biochemistry, and physiology of the UPS with emphasis on its role in the heart, if known. In addition, evidence will be presented supporting the role of certain muscle-specific ubiquitin protein ligases, key regulatory components of the UPS, in regulation of sarcomere protein turnover and cardiomyocyte size and how this might play a role in induction of the hypertrophic phenotype. Moreover, this review will present the evidence suggesting that proteasomal dysfunction may play a role in cardiac pathologies such as myocardial ischemia, congestive heart failure, and myofilament-related and idiopathic-dilated cardiomyopathies, as well as cardiomyocyte loss in the aging heart. Finally, certain pitfalls of proteasome studies will be described with the intent of providing investigators with enough information to avoid these problems. This review should provide current investigators in the field with an up-to-date analysis of the literature and at the same time provide an impetus for new investigators to enter this important and rapidly changing area of research.
Regulation of baseline Ca2+sensitivity in permeabilized uterine arteries: effect of pregnancy
Authors: Xiao Daliao , Huang Xiaohui , Longo Lawrence D. , Pearce William J. , Zhang Lubo
Published: February 2006

The adaptation of contractile mechanisms of the uterine artery to pregnancy is not fully understood. The present study examined the effect of pregnancy on the uterine artery baseline Ca2+sensitivity. In β-escin-permeabilized arterial preparations, Ca2+-induced concentration-dependent contractions were significantly decreased in uterine arteries from pregnant animals compared with those of nonpregnant animals. Time-course studies showed that Ca2+increased phosphorylation of 20-kDa myosin light chain (MLC20), which preceded the tension development in vessels from both pregnant and nonpregnant animals. When compared with vessels from nonpregnant animals, there was a significant increase in the protein level of MLC20and an accordance increase in the level of Ca2+-induced phosphorylated MLC20(MLC20-P) in uterine arteries during pregnancy. Simultaneous measurements of MCL20-P levels and contractions stimulated with Ca2+in the same tissues demonstrated a significant attenuation in the tension-to-MLC20-P ratio in uterine arteries during pregnancy. Activation of PKC with phorbol 12,13-dibutyrate (PDBu) potentiated Ca2+-induced contractions in uterine arteries from nonpregnant but not pregnant animals. Accordingly, inhibition of PKC attenuated Ca2+-induced contractions in uterine arteries from nonpregnant but not pregnant animals. PDBu produced contractions in the presence or absence of Ca2+in the β-escin-permeabilized arteries, which were significantly decreased in uterine arteries from pregnant compared with nonpregnant animals. The results suggest that pregnancy upregulates the thick-filament regulatory pathway by increasing MLC20phosphorylation but downregulates the thin-filament regulatory pathway by decreasing the contractile sensitivity of MLC20-P, resulting in attenuated baseline Ca2+sensitivity in the uterine artery. In addition, PKC plays an important role in the regulation of basal Ca2+sensitivity, which is downregulated during pregnancy.
Changes in end-to-end interactions of tropomyosin affect mouse cardiac muscle dynamics
Authors: Gaffin Robert D. , Gokulan Kuppan , Sacchettini James C. , Hewett Timothy E. , Klevitsky Raisa , Robbins Jeffrey , Sarin Vandana , Zawieja David C. , Meininger Gerald A. , Muthuchamy Mariappan
Published: February 2006

The ends of striated muscle tropomyosin (TM) are integral for thin filament cooperativity, determining the cooperative unit size and regulating the affinity of TM for actin. We hypothesized that altering the α-TM carboxy terminal overlap end to the β-TM counterpart would affect the amino-terminal association, which would alter the end-to-end interactions of TM molecules in the thin filament regulatory strand and affect the mechanisms of cardiac muscle contraction. To test this hypothesis, we generated transgenic (TG) mouse lines that express a mutant form of α-TM in which the first 275 residues are from α-TM and the last nine amino acids are from β-TM (α-TM9aaΔβ). Molecular analyses show that endogenous α-TM mRNA and protein are nearly completely replaced with α-TM9aaΔβ. Working heart preparations data show that the rates of contraction and relaxation are reduced in α-TM9aaΔβ hearts. Left ventricular pressure and time to peak pressure are also reduced (−12% and −13%, respectively). The ratio of maximum to minimum first derivatives of change in left ventricular systolic pressure with respect to time (ratio of +dP/d t to −dP/d t, respectively) is increased, but τ is not changed significantly. Force-intracellular calcium concentration ([Ca2+]i) measurements from intact papillary fibers demonstrate that α-TM9aaΔβ TG fibers produce less force per given [Ca2+]icompared with nontransgenic fibers. Taken together, the data demonstrate that the rate of contraction is primarily affected in TM TG hearts. Protein docking studies show that in the mutant molecule, the overall carbon backbone is perturbed about 1.5 Å, indicating that end-to-end interactions are altered. These results demonstrate that the localized flexibility present in the coiled-coil structures of TM isoforms is different, and that plays an important role in interacting with neighboring thin filament regulatory proteins and with differentially modulating the myofilament activation processes.
Determinants of coronary flow velocity reserve in healthy young men
Authors: Kiviniemi Tuomas O. , Snapir Amir , Saraste Markku , Toikka Jyri O. , Raitakari Olli T. , Ahotupa Markku , Hartiala Jaakko J. , Scheinin Mika , Koskenvuo Juha W.
Published: February 2006

The objective of this study was to identify risk markers for attenuated coronary flow velocity reserve (CFVR) that exist in healthy young men without evident atherosclerotic risk factors. Coronary blood flow velocity was measured with transthoracic Doppler echocardiography at baseline and during adenosine infusion in 37 healthy nonsmoking men [mean age, 27 yr (SD 4.0)]. Body composition and distribution of fat tissue were assessed with anthropometric measures and regulation of fat metabolism by determination of adiponectin and leptin levels. Physical performance capacity was tested with ergospirometry. The mean body mass index was 23 kg/m2 (SD 1.9), waist-to-hip ratio was 0.84 (SD 0.04), and CFVR was 3.5 (SD 0.61). Obesity indexes at study outset, leptin, adiponectin, maximal load (Max load in W/kg) and maximal oxygen consumption (V̇o2 peak in ml·kg−1·min−1) in ergospirometry, rate-pressure product, and heart rate at rest were significantly associated with CFVR. In multivariate analysis, Max load (in W/kg) and waist-to-hip ratio were the only independent predictors of CFVR. We found no relationship between CFVR and serum lipids or body mass index. We conclude that abdominal fat accumulation and low aerobic fitness are independently associated with CFVR in men.
PPAR-α activator fenofibrate increases renal CYP-derived eicosanoid synthesis and improves endothelial dilator function in obese Zucker rats
Authors: Zhao Xueying , Quigley Jeffrey E. , Yuan Jianghe , Wang Mong-Heng , Zhou Yiqing , Imig John D.
Published: February 2006

Previous studies have shown that the synthesis of renal cytochrome P-450 (CYP)-derived eicosanoids is downregulated in genetic or high-fat diet-induced obese rats. Experiments were designed to determine whether fenofibrate, a peroxisome proliferator-activated receptor (PPAR)-α agonist, would induce renal eicosanoid synthesis and improve endothelial function in obese Zucker rats. Administration of fenofibrate (150 mg·kg−1·day−1for 4 wk) significantly reduced plasma insulin, triglyceride, and total cholesterol levels in obese Zucker rats. CYP2C11 and CYP2C23 proteins were downregulated in renal vessels of obese Zucker rats. Consequently, renal vascular epoxygenase activity decreased by 15% in obese Zucker rats compared with lean controls. Chronic fenofibrate treatment significantly increased renal cortical and vascular CYP2C11 and CYP2C23 protein levels in obese Zucker rats, whereas it had no effect on epoxygenase protein and activity in lean Zucker rats. Renal cortical and vascular epoxygenase activities were consequently increased by 54% and 18%, respectively, in fenofibrate-treated obese rats. In addition, acetylcholine (1 μM)-induced vasodilation was significantly reduced in obese Zucker kidneys (37% ± 11%) compared with lean controls (67% ± 9%). Chronic fenofibrate administration increased afferent arteriolar responses to 1 μM of acetylcholine in obese Zucker rats (69% ± 4%). Inhibition of the epoxygenase pathway with 6-(2-propargyloxyphenyl)hexanoic acid attenuated afferent arteriolar diameter responses to acetylcholine to a greater extent in lean compared with obese Zucker rats. These results demonstrate that the PPAR-α agonist fenofibrate increased renal CYP-derived eicosanoids and restored endothelial dilator function in obese Zucker rats.
Transit time dispersion in pulmonary and systemic circulation: effects of cardiac output and solute diffusivity
Authors: Weiss Michael , Krejcie Tom C. , Avram Michael J.
Published: February 2006

We present an in vivo method for analyzing the distribution kinetics of physiological markers into their respective distribution volumes utilizing information provided by the relative dispersion of transit times. Arterial concentration-time curves of markers of the vascular space [indocyanine green (ICG)], extracellular fluid (inulin), and total body water (antipyrine) measured in awake dogs under control conditions and during phenylephrine or isoproterenol infusion were analyzed by a recirculatory model to estimate the relative dispersions of transit times across the systemic and pulmonary circulation. The transit time dispersion in the systemic circulation was used to calculate the whole body distribution clearance, and an interpretation is given in terms of a lumped organ model of blood-tissue exchange. As predicted by theory, this relative dispersion increased linearly with cardiac output, with a slope that was inversely related to solute diffusivity. The relative dispersion of the flow-limited indicator antipyrine exceeded that of ICG (as a measure of intravascular mixing) only slightly and was consistent with a diffusional equilibration time in the extravascular space of ∼10 min, except during phenylephrine infusion, which led to an anomalously high relative dispersion. A change in cardiac output did not alter the heterogeneity of capillary transit times of ICG. The results support the view that the relative dispersions of transit times in the systemic and pulmonary circulation estimated from solute disposition data in vivo are useful measures of whole body distribution kinetics of indicators and endogenous substances. This is the first model that explains the effect of flow and capillary permeability on whole body distribution of solutes without assuming well-mixed compartments.
Myocyte apoptosis during acute myocardial infarction in rats is related to early sarcolemmal translocation of annexin A5 in border zone
Authors: Monceau Virginie , Belikova Yulia , Kratassiouk Gueorgui , Robidel Estelle , Russo-Marie Françoise , Charlemagne Daniele
Published: February 2006

Annexin A5 is a Ca2+-dependent phospholipid binding protein well known for its high phosphatidylserine affinity. In vitro, translocation to sarcolemma and externalization of endogenous annexin A5 in the cardiomyocyte has recently been demonstrated to exert a proapoptotic effect. To determine whether these in vitro findings occurred in vivo, we performed myocardial infarction (MI) and studied the time course of apoptosis and annexin A5 localization (0.5 to 8 h) in the border zone around the infarcted area. This zone that was defined as Evans blue unstained and triphenyltetrazolium chloride (TTC) stained, represented 42.3 ± 5.5% of the area at risk and showed apoptotic characteristics (significant increases in caspase 3 activity 2.3-fold at 0.5 h; P < 0.05), transferase-mediated dUTP nick-end labeling-positive cardiomyocytes (15.8 ± 0.8% at 8 h), and DNA ladder. When compared with sham-operated rats, we found that in this area, annexin A5 was translocated to the sarcolemma as early as 0.5 h after MI and that translocation increased with time. Moreover, the amount of annexin A5 was unchanged in the border zone and decreased in the infarcted area after 1 h (77.1 ± 4.8%; P < 0.01 vs. perfused area), suggesting a release in the latter but not in the former. In conclusion, we demonstrated that annexin A5 translocation is an early and rapid event of the whole border zone, likely due to Ca2+increase. Part of this translocation occurred in areas where apoptosis was later detected and suggests that in vivo as in vitro annexin A5 might be involved in the regulation of early apoptotic events during cardiac pathological situations.
Protection of adult rat cardiac myocytes from ischemic cell death: role of caveolar microdomains and δ-opioid receptors
Authors: Patel Hemal H. , Head Brian P. , Petersen Heidi N. , Niesman Ingrid R. , Huang Diane , Gross Garrett J. , Insel Paul A. , Roth David M.
Published: February 2006

The role of caveolae, membrane microenvironments enriched in signaling molecules, in myocardial ischemia is poorly defined. In the current study, we used cardiac myocytes prepared from adult rats to test the hypothesis that opioid receptors (OR), which are capable of producing cardiac protection in vivo, promote cardiac protection in cardiac myocytes in a caveolae-dependent manner. We determined protein expression and localization of δ-OR (DOR) using coimmunohistochemistry, caveolar fractionation, and immunoprecipitations. DOR colocalized in fractions with caveolin-3 (Cav-3), a structural component of caveolae in muscle cells, and could be immunoprecipitated by a Cav-3 antibody. Immunohistochemistry confirmed plasma membrane colocalization of DOR with Cav-3. Cardiac myocytes were subjected to simulated ischemia (2 h) or an ischemic preconditioning (IPC) protocol (10 min ischemia, 30 min recovery, 2 h ischemia) in the presence and absence of methyl-β-cyclodextrin (MβCD, 2 mM), which binds cholesterol and disrupts caveolae. We also assessed the cardiac protective effects of SNC-121 (SNC), a selective DOR agonist, on cardiac myocytes with or without MβCD and MβCD preloaded with cholesterol. Ischemia, simulated by mineral oil layering to inhibit gas exchange, promoted cardiac myocyte cell death (trypan blue staining), a response blunted by SNC (37 ± 3 vs. 59 ± 3% dead cells in the presence and absence of 1 μM SNC, respectively, P < 0.01) or by use of the IPC protocol (35 ± 4 vs. 62 ± 3% dead cells, P < 0.01). MβCD treatment, which disrupted caveolae (as detected by electron microscopy), fully attenuated the protective effects of IPC or SNC, resulting in cell death comparable to that of the ischemic group. By contrast, SNC-induced protection was not abrogated in cells incubated with cholesterol-saturated MβCD, which maintained caveolae structure and function. These findings suggest a key role for caveolae, perhaps through enrichment of signaling molecules, in contributing to protection of cardiac myocytes from ischemic damage.
Heart rate recovery after maximal exercise is associated with acetylcholine receptor M2 (CHRM2) gene polymorphism
Authors: Hautala Arto J. , Rankinen Tuomo , Kiviniemi Antti M. , Mäkikallio Timo H. , Huikuri Heikki V. , Bouchard Claude , Tulppo Mikko P.
Published: February 2006

The determinants of heart rate (HR) recovery after exercise are not well known, although attenuated HR recovery is associated with an increased risk of cardiovascular mortality. Because acetylcholine receptor subtype M2 (CHRM2) plays a key role in the cardiac chronotropic response, we tested the hypothesis that, in healthy individuals, the CHRM2 gene polymorphisms might be associated with HR recovery 1 min after the termination of a maximal exercise test, both before and after endurance training. The study population consisted of sedentary men and women ( n = 95, 42 ± 5 yr) assigned to a training ( n = 80) or control group ( n = 15). The study subjects underwent a 2-wk laboratory-controlled endurance training program, which included five 40-min sessions/wk at 70–80% of maximal HR. HR recovery differed between the intron 5 rs324640 genotypes at baseline (C/C, −33 ± 10; C/T, −33 ± 7; and T/T, −40 ± 11 beats/min, P = 0.008). Endurance training further strengthened the association: the less common C/C homozygotes showed 6 and 12 beats/min lower HR recovery than the C/T heterozygotes or the T/T homozygotes ( P = 0.001), respectively. A similar association was found between A/T transversion at the 3′-untranslated region of the CHRM2 gene and HR recovery at baseline ( P = 0.025) and after endurance training ( P = 0.005). These data suggest that DNA sequence variation at the CHRM2 locus is a potential modifier of HR recovery in the sedentary state and after short-term endurance training in healthy individuals.
Inhibition of phospholipase C-γ1augments the decrease in cardiomyocyte viability by H2O2
Authors: Mangat Rabban , Singal Tushi , Dhalla Naranjan S. , Tappia Paramjit S.
Published: February 2006

The present study was conducted to examine the role of a major cardiac phospholipase C (PLC) isozyme, PLC-γ1, in cardiomyocytes during oxidative stress. Left ventricular cardiomyocytes were isolated by collagenase digestion from adult male Sprague-Dawley rats (250–300 g) and treated with 20, 50, and 100 μM H2O2for 15 min. A concentration-dependent (up to 50 μM) increase in the mRNA level and membrane protein content of PLC-γ1was observed with H2O2treatment. Furthermore, PLC-γ1was activated in response to H2O2, as revealed by an increase in the phosphorylation of its tyrosine residues. There was a marked increase in the phosphorylation of the antiapoptotic protein Bcl-2 by H2O2; this change was attenuated by a PLC inhibitor, U-73122. Although both protein kinase C (PKC)-δ and -ε protein contents were increased in the cardiomyocyte membrane fraction in response to H2O2, PKC-ε activation, unlike PKC-δ, was attenuated by U-73122 (2 μM). Inhibition of PKC-ε with inhibitory peptide (0.1 μM) prevented Bcl-2 phosphorylation. Moreover, different concentrations (0.05, 0.1, and 0.2 μM) of this peptide augmented the decrease in cardiomyocyte viability in response to H2O2. In addition, a decrease in cardiomyocyte viability, as assessed by trypan blue exclusion, due to H2O2was also seen when cells were pretreated with U-73122 and was as a result of increased apoptosis. It is therefore suggested that PLC-γ1may play a role in cardiomyocyte survival during oxidative stress via PKC-ε and phosphorylation of Bcl-2.