bluuebunny/crossref_metadata_2025 huggingface dataset:
Sympathetic control after cardiac resynchronization therapy: responders versus nonresponders
Authors: Najem Boutaïna , Unger Philippe , Preumont Nicolas , Jansens Jean-Luc , Houssière Anne , Pathak Atul , Xhaet Olivier , Gabriel Laurence , Friart Alain , De Roy Luc , Vandenbossche Jean-Luc , van de Borne Philippe
Published: July 2006

Cardiac resynchronization therapy (CRT) decreases muscle sympathetic nerve activity (MSNA) in patients with severe congestive heart failure (CHF) and cardiac asynchrony. Whether this affects equally patients who clinically respond or not to CRT is unknown. We tested the hypothesis that the favorable effects of CRT on MSNA disappear on CRT interruption only in those who respond to CRT. Twenty-three consecutive CHF patients participated in the study, among whom 16 presented a symptomatic improvement by one or more New York Heart Association (NYHA) functional classes 15 ± 5 mo after CRT (responders), and seven had not improved after 12 ± 4 mo of CRT (nonresponders). MSNA and echocardiographic recordings were obtained in random order during atrio-right ventricular pacing (ARV), without stimulation in patients who were not pacemaker dependent (OFF, n = 17), and during atrio-biventricular pacing (BIV). Responders had a longer 6-min walking distance, a lower NYHA class and brain natriuretic peptide levels, and a better quality of life than did nonresponders (all P < 0.05). MSNA increased by 25 ± 7% in the responders, whereas it remained unchanged in the nonresponders, when shifting from the BIV mode to a nonsynchronous condition (ARV and OFF modes) ( P < 0.01). Cardiac output decreased by 0.7 ± 0.2 l/min in the responders but did not change when shifting from the BIV mode to the nonsynchronous pacing mode in the nonresponders ( P < 0.01). In conclusion, reversible sympathoinhibition is a marker of the clinical response to CRT.
Odor-specific effects on reentrainment following phase advances in the diurnal rodent, Octodon degus
Authors: Jechura Tammy J. , Mahoney Megan M. , Stimpson Cheryl D. , Lee Theresa M.
Published: July 2006

Reentrainment following phase shifts of the light-dark (LD) cycle is accelerated in Octodon degus in the presence of olfactory social cues (i.e., odors) produced by conspecifics. However, not all odors from conspecifics were effective in facilitating reentrainment after a phase advance. In the current experiments, we examined whether nonanimal odors, odors from another species, or conspecific odors, including those manipulated by steroid hormones, can cause the same increased reentrainment of wheel-running activity as odors from an intact, adult female degu. A variety of odors, each selected to probe a particular aspect of the reentrainment acceleration phenomenon, were presented to a group of phase-shifting female degus. The shifting females (test animals) responded to odors of intact, female degu donors with decreased reentrainment time, but odors of ovariectomized (OVX), OVX with a single hormone replacement capsule (estradiol or progesterone) or phase-shifting females had no effect. Multiple males were effective odor donors, whereas a single male was ineffective in earlier studies. Rats and cloves were not effective in accelerating reentrainment. Furthermore, odors from rats delayed reentrainment. We conclude that the odors that effectively accelerate degu reentrainment after a phase advance of the LD cycle are species specific. We also report that repeated phase shifts, followed by complete recovery of phase relationships, do not alter the rate of recovery from a phase shift over time. These data suggest that in O. degus, a social species, odors may reinforce and strengthen the salience of the photic zeitgeber and/or facilitate synchronization of rhythms between animals.
A metabolic basis for impaired muscle force production and neuromuscular compensation during sprint cycling
Authors: Bundle Matthew W. , Ernst Carrie L. , Bellizzi Matthew J. , Wright Seth , Weyand Peter G.
Published: July 2006

For both different individuals and modes of locomotion, the external forces determining all-out sprinting performances fall predictably with effort duration from the burst maximums attained for 3 s to those that can be supported aerobically as trial durations extend to roughly 300 s. The common time course of this relationship suggests a metabolic basis for the decrements in the force applied to the environment. However, the mechanical and neuromuscular responses to impaired force production (i.e., muscle fatigue) are generally considered in relation to fractions of the maximum force available, or the maximum voluntary contraction (MVC). We hypothesized that these duration-dependent decrements in external force application result from a reliance on anaerobic metabolism for force production rather than the absolute force produced. We tested this idea by examining neuromuscular activity during two modes of sprint cycling with similar external force requirements but differing aerobic and anaerobic contributions to force production: one- and two-legged cycling. In agreement with previous studies, we found greater peak per leg aerobic metabolic rates [59% (±6 SD)] and pedal forces at V̇o2 peak [30% (±9)] during one- vs. two-legged cycling. We also determined downstroke pedal forces and neuromuscular activity by surface electromyography during 15 to 19 all-out constant load sprints lasting from 12 to 400 s for both modes of cycling. In support of our hypothesis, we found that the greater reliance on anaerobic metabolism for force production induced compensatory muscle recruitment at lower pedal forces during two- vs. one-legged sprint cycling. We conclude that impaired muscle force production and compensatory neuromuscular activity during sprinting are triggered by a reliance on anaerobic metabolism for force production.
Renal NF-κB activation and TNF-α upregulation correlate with salt-sensitive hypertension in Dahl salt-sensitive rats
Authors: Gu Jian-Wei , Tian Niu , Shparago Megan , Tan Wei , Bailey Amelia P. , Manning R. Davis
Published: July 2006

Molecular mechanisms of salt-sensitive (SS) hypertension related to renal inflammation have not been defined. We seek to determine whether a high-salt (HS) diet induces renal activation of NF-κB and upregulation of TNF-α related to the development of hypertension in Dahl SS rats. Six 8-wk-old male Dahl SS rats received a HS diet (4%), and six Dahl SS rats received a low-sodium diet (LS, 0.3%) for 5 wk. In the end, mean arterial pressure was determined in conscious rats by continuous monitoring through a catheter placed in the carotid artery. Mean arterial pressure was significantly higher in the HS than the LS group (177.9 ± 3.7 vs. 109.4 ± 2.9 mmHg, P < 0.001). There was a significant increase in urinary albumin secretion in the HS group compared with the LS group (22.3 ± 2.6 vs. 6.1 ± 0.7 mg/day; P < 0.001). Electrophoretic mobility shift assay demonstrated that the binding activity of NF-κB p65 proteins in the kidneys of Dahl SS rats was significantly increased by 53% in the HS group compared with the LS group ( P = 0.007). ELISA indicated that renal protein levels of TNF-α, but not IL-6, interferon-γ, and CCL28, were significantly higher in the HS than the LS group (2.3 ± 0.8 vs. 0.7 ± 0.2 pg/mg; P = 0.036). We demonstrated that plasma levels of TNF-α were significantly increased by fivefold in Dahl SS rats on a HS diet compared with a LS diet. Also, we found that increased physiologically relevant sodium concentration (10 mmol/l) directly stimulated NF-κB activation in cultured human renal proximal tubular epithelial cells. These findings support the hypothesis that activation of NF-κB and upregulation of TNF-α are the important renal mechanisms linking proinflammatory response to SS hypertension.
Repeated exposures to daytime bright light increase nocturnal melatonin rise and maintain circadian phase in young subjects under fixed sleep schedule
Authors: Takasu Nana N. , Hashimoto Satoko , Yamanaka Yujiro , Tanahashi Yusuke , Yamazaki Ayano , Honma Sato , Honma Ken-ichi
Published: July 2006

Effects of two different light intensities during daytime were examined on human circadian rhythms in plasma melatonin, core body temperature, and wrist activity under a fixed sleep schedule. Sleep qualities as indicated by polysomnography and subjective sleepiness were also measured. In the first week, under dim light conditions (∼10 lx), the onset and peak of nocturnal melatonin rise were significantly delayed, whereas the end of melatonin rise was not changed. The peak level of melatonin rise was not affected. As a result, the width of nocturnal melatonin rise was significantly shortened. In the second week, under bright light conditions (∼5,000 lx), the phases of nocturnal melatonin rise were not changed further, but the peak level was significantly increased. Core body temperature at the initial sleep phase was progressively elevated during the course of dim light exposure and reached the maximum level at the first night of bright light conditions. Subjective sleepiness gradually declined in the course of dim light exposure and reached the minimum level at the first day of bright light. These findings indicate that repeated exposures to daytime bright light are effective in controlling the circadian phase and increasing the peak level of nocturnal melatonin rise in plasma and suggest a close correlation between phase-delay shifts of the onset of nocturnal melatonin rise or body temperature rhythm and daytime sleepiness.
Descending vasa recta endothelium is an electrical syncytium
Authors: Zhang Qingli , Cao Chunhua , Mangano Michael , Zhang Zhong , Silldorff Erik P. , Lee-Kwon Whaseon , Payne Kristie , Pallone Thomas L.
Published: July 2006

We examined gap junction coupling of descending vasa recta (DVR). DVR endothelial cells or pericytes were depolarized to record the associated capacitance transients. Virtually all endothelia and some pericytes exhibited prolonged transients lasting 10–30 ms. Carbenoxolone (100 μM) and 18β-glycyrrhetinic acid (18βGRA; 100 μM) markedly shortened the endothelial transients. Carbenoxolone and heptanol (2 mM) reduced the pericyte capacitance transients when they were prolonged. Lucifer yellow (LY; 2 mM) was dialyzed into the cytoplasm of endothelial cells and pericytes. LY spread diffusely along the endothelial monolayer, whereas in most pericytes, it was confined to a single cell. In some pericytes, complex patterns of LY spreading were observed. DVR cells were depolarized by voltage clamp as fluorescence of bis(1,3-dibarbituric acid)-trimethine oxanol [DiBAC4( 3 )] was monitored ∼200 μm away. A 40-mV endothelial depolarization was accompanied by a 26.1 ± 5.5-mV change in DiBAC4( 3 ) fluorescence. DiBAC4( 3 ) fluorescence did not change after 18βGRA or when pericytes were depolarized. Similarly, propagated cytoplasmic Ca2+responses arising from mechanical perturbation of the DVR wall were attenuated by 18βGRA or heptanol. Connexin (Cx) immunostaining showed predominant linear Cx40 and Cx43 in endothelia, whereas Cx37 stained smooth muscle actin-positive pericytes. We conclude that the DVR endothelium is an electrical syncytium and that gap junction coupling in DVR pericytes exists but is less pronounced.
Effects of central or peripheral leptin administration on norepinephrine turnover in defined fat depots
Authors: Penn Dawn M. , Jordan Lisa C. , Kelso Emily W. , Davenport Jessica E. , Harris Ruth B. S.
Published: July 2006

Leptin preserves lean tissue but decreases adipose tissue by increasing lipolysis and/or inhibiting lipogenesis. The sympathetic nervous system (SNS) is a primary regulator of lipolysis, but it is not known if leptin increases norepinephrine turnover (NETO) in white adipose tissue. In this study, we examined the effect of leptin administered either as a chronic physiological dose (40 μg/day for 4 days from ip miniosmotic pumps) or as an acute injection in the third ventricle (1.5 μg injected two times daily for 2 days) on NETO and the size of brown and white fat depots in male Sprague Dawley rats. NETO was determined from the decline in tissue norepinephrine (NE) during 4 h following administration of the NE synthesis inhibitor α-methyl-para-tryrosine. The centrally injected leptin-treated animals demonstrated more dramatic reductions in food intake, body weight, and fat pad size and an increase in NETO compared with the peripherally infused animals. Neither route of leptin administration caused a uniform increase in NETO across all fat pads tested, and in both treatment conditions leptin decreased the size of certain fat pads independent of an increase in NETO. Similar discrepancies in white fat NETO were found for rats pair fed to leptin-treated animals. These results demonstrate that leptin acting either centrally or peripherally selectively increases sympathetic outflow to white fat depots and that a leptin-induced change in fat pad weight does not require an increase in NETO.
The median preoptic nucleus is involved in the facilitation of heat-escape/cold-seeking behavior during systemic salt loading in rats
Authors: Konishi Masahiro , Kanosue Kazuyuki , Kano Masumi , Kobayashi Akiko , Nagashima Kei
Published: July 2006

Systemic salt loading has been reported to facilitate operant heat-escape/cold-seeking behavior. In the present study, we hypothesized that the median preoptic nucleus (MnPO) would be involved in this mechanism. Rats were divided into two groups ( n = 6 each): one group had the MnPO lesion with ibotenic acid (4.0 μg) and the other was the vehicle control. After subcutaneous injection (10 ml/kg) of either isotonic- (154 mM) or hypertonic-saline (2,500 mM), each rat was placed in a behavior box, where the ambient temperature was changed to 26°C, 35°C, and 40°C every 1 h. The position of a rat in the box and the body core temperature (Tcore) were monitored. A rat could trigger 0°C air for 45 s in the 35°C and 40°C heat when moved in a specific area in the box (operant behavior). In the control group, counts of the operant behavior were greater ( P < 0.05) in the hypertonic- than in the isotonic-saline injection (17 ± 2 and 10 ± 2 at 35°C, 24 ± 2 and 18 ± 1 at 40°C). Tcore remained unchanged throughout the exposure, although the level was lower ( P < 0.05) in the hypertonic- than in the isotonic-saline trial (36.6 ± 0.2°C and 37.4 ± 0.1°C at 26°C and 36.9 ± 0.2°C and 37.4 ± 0.1°C at 40°C, respectively). However, in the MnPO-lesion group, counts of the behavior were similar between the hypertonic- and isotonic-saline injection trials (10 ± 2 and 8 ± 1 at 35°C, and 17 ± 1 and 16 ± 1 at 40°C, respectively). Tcore increased ( P < 0.05) in the heat in both trials (36.8 ± 0.1°C and 37.4 ± 0.1°C at 26°C and 37.4 ± 0.2°C and 37.8 ± 0.2°C at 40°C in the hypertonic- and isotonic-saline injection trials, respectively). These results may suggest that, at least in part, the MnPO is involved in the facilitation of heat-escape/cold-seeking behavior during osmotic stimulation.
Nocturnal growth hormone secretory dynamics are altered after resistance exercise: deconvolution analysis of 12-hour immunofunctional and immunoreactive isoforms
Authors: Tuckow Alexander P. , Rarick Kevin R. , Kraemer William J. , Marx James O. , Hymer Wesley C. , Nindl Bradley C.
Published: July 2006

To characterize the effects of daytime exercise on subsequent overnight growth hormone (GH) secretion and elimination dynamics, serum was sampled, and GH was measured every 10 min for 12 h (1800 to 0600) in a control (CON) condition and after a 50-set resistance exercise protocol (EX) from 1500 to 1700. GH was measured with a conventional immunoreactive (IR) and an immunofunctional (IF) assay, and values were analyzed via a multi-parameter deconvolution analysis. EX resulted in a higher overnight secretory burst frequency [CON: 7.6 (SD 2.4) < EX: 9.4 (2.2) bursts per 12 h, P = 0.005] but lower mean burst mass [CON: 9.2 (4.7) > EX: 6.0 (2.9) μg/l, P = 0.019] and secretory rate [CON: 0.68 (0.29) > EX: 0.48 (0.23) μg/l/min; P = 0.015; ANOVA main effect means presented]. Approximate entropy (ApEn) was greater after EX, indicating a less orderly GH release process than CON. The estimated half-life of IF GH was significantly lower than IR GH [IF: 15.3 (1.1) < IR 19.8 (1.6) min, P < 0.001] but similar between the CON and EX conditions (∼17 min). Despite the changes in secretory dynamics, 12-h mean and integrated GH concentrations were similar between conditions. The results suggest that although quantitatively similar total amounts of GH are secreted overnight in CON and EX conditions, resistance exercise alters the dynamics of secretion by attenuating burst mass and amplitude yet increasing burst frequency.
Role of nitrogen in transmucosal gas exchange rate in the rat middle ear
Authors: Kania Romain E. , Herman Philippe , Huy Patrice Tran Ba , Ar Amos
Published: July 2006

This study investigates the role of nitrogen (N2) in transmucosal gas exchange of the middle ear (ME). We used an experimental rat model to measure gas volume variations in the ME cavity at constant pressure. We disturbed the steady-state gas composition with either air or N2 to measure resulting changes in volume at ambient pressure. Changes in gas volume over time could be characterized by three phases: a primary transient increase with time (phase I), followed by a linear decrease (phase II), and then a gradual decrease (phase III). The mean slope of phase II was −0.128 μl/min (SD 0.023) in the air group ( n = 10) and −0.105 μl/min (SD 0.032) in the N2 group ( n = 10), but the difference was not significant ( P = 0.13), which suggests that the rate of gas loss can be attributed mainly to the same steady-state partial pressure gradient of N2 reached in this phase. Furthermore, a mathematical model was developed analyzing the transmucosal N2 exchange in phase II. The model takes gas diffusion into account, predicting that, in the absence of change in mucosal blood flow rate, gas volume in the ME should show a linear decrease with time after steady-state conditions and gas composition are established. In accordance with the experimental results, the mathematical model also suggested that transmucosal gas absorption of the rat ME during steady-state conditions is governed mainly by diffusive N2 exchange between the ME gas and its mucosal blood circulation.
How the body controls brain temperature: the temperature shielding effect of cerebral blood flow
Authors: Zhu Mingming , Ackerman Joseph J. H. , Sukstanskii Alexander L. , Yablonskiy Dmitriy A.
Published: July 2006

Normal brain functioning largely depends on maintaining brain temperature. However, the mechanisms protecting brain against a cooler environment are poorly understood. Reported herein is the first detailed measurement of the brain-temperature profile. It is found to be exponential, defined by a characteristic temperature shielding length, with cooler peripheral areas and a warmer brain core approaching body temperature. Direct cerebral blood flow (CBF) measurements with microspheres show that the characteristic temperature shielding length is inversely proportional to the square root of CBF in excellent agreement with a theoretical model. This “temperature shielding effect” quantifies the means by which CBF prevents “extracranial cold” from penetrating deep brain structures. The effect is crucial for research and clinical applications; the relationship between brain, body, and extracranial temperatures can now be quantitatively predicted.
Proteolytic mRNA expression in response to acute resistance exercise in human single skeletal muscle fibers
Authors: Yang Yifan , Jemiolo Bozena , Trappe Scott
Published: July 2006

The purpose of this study was to characterize changes in mRNA expression of select proteolytic markers in human slow-twitch [myosin heavy chain (MHC) I] and fast-twitch (MHC IIa) single skeletal muscle fibers following a bout of resistance exercise (RE). Muscle biopsies were obtained from the vastus lateralis of eight young healthy sedentary men [23 ± 2 yr (mean ± SD), 93 ± 17 kg, 183 ± 6 cm] before and 4 and 24 h after 3 × 10 repetitions of bilateral knee extensions at 65% of one repetition maximum. The mRNA levels of TNF-α, calpains 1 and 2, muscle RING (really interesting novel gene) finger-1 (MuRF-1), atrogin-1, caspase-3, B-cell leukemia/lymphoma (Bcl)-2, and Bcl-2-associated X protein (Bax) were quantified using real-time RT-PCR. Generally, MHC I fibers had higher (1.6- to 5.0-fold, P < 0.05) mRNA expression pre- and post-RE. One exception was a higher (1.6- to 3.9-fold, P < 0.05) Bax-to-Bcl-2 mRNA ratio in MHC IIa fibers pre- and post-RE. RE increased (1.4- to 4.8-fold, P < 0.05) MuRF-1 and caspase-3 mRNA levels 4–24 h post-RE in both fiber types, whereas Bax-to-Bcl-2 mRNA ratio increased 2.2-fold ( P < 0.05) at 4 h post-RE only in MHC I fibers. These results suggest that MHC I fibers have a greater proteolytic mRNA expression pre- and post-RE compared with MHC IIa fibers. The greatest mRNA induction following RE was in MuRF-1 and caspase-3 in both fiber types. This altered and specific proteolytic mRNA expression among slow- and fast-twitch muscle fibers indicates that the ubiquitin/proteasomal and caspase pathways may play an important role in muscle remodeling with RE.
Venous smooth muscle tone and responsiveness in older adults
Authors: Young Colin N. , Stillabower Michael E. , DiSabatino Angela , Farquhar William B.
Published: July 2006

Venous compliance is lower in older adults compared with younger adults. It is possible that alterations in venous smooth muscle tone and responsiveness may contribute to the age-related differences in venous compliance. To determine the effects of sympathetic activation [cold pressor test (cold pressor test); rhythmic ischemic handgrip (rhythmic ischemic handgrip)] and endothelium-independent decreases in smooth muscle tone [sublingual nitroglycerin (nitroglycerin)] on venous compliance in young and older adults, forearm and calf venous compliance was measured in 12 young (22 ± 1 yr) and 12 old (65 ± 1 yr) supine subjects using venous occlusion plethysmography. Venous compliance was assessed at baseline, during the cold pressor test and rhythmic ischemic handgrip tests, and after nitroglycerin administration. All pressure-volume relationships were modeled with a quadratic regression equation, and β1and β2were used as indexes of venous compliance. A repeated-measures ANOVA was used to determine the effect of the age and trial on venous compliance. Calf regression parameters β1(0.0639 ± 0.0126 vs. 0.0503 ± 0.0059, young vs. older; P < 0.05) and β2(−0.00054 ± 0.00011 vs. −0.00041 ± 0.00005, young vs. older; P < 0.05) were significantly less in older adults at baseline. Similarly, forearm regression parameters, β1and β2were lower in older adults at baseline. Venous compliance was not effected by the cold pressor test test, rhythmic ischemic handgrip, or sublingual nitroglycerin in either group. Data suggest that forearm and calf venous compliance is lower in older adults compared with young. However, this difference probably cannot be explained by alterations in smooth muscle tone or responsiveness.
Tumor necrosis factor-α promotes the accumulation of neutrophils and macrophages in skeletal muscle
Authors: Peterson Jennifer M. , Feeback Kevin D. , Baas Joel H. , Pizza Francis X.
Published: July 2006

Tumor necrosis factor-α (TNF-α) has been associated with cachexia and is known to regulate multiple inflammatory cell (neutrophil and macrophage) responses. We tested the hypothesis that neutrophils and macrophages accumulate in the extensor digitorum longus (EDL) and soleus muscles of mice after chronic TNF-α administration. Murine recombinant TNF-α (∼100 μg·kg−1·day−1) in vehicle solution or vehicle solution alone (sham) was administered to C57BL/6 mice for 7 days via osmotic minipumps. In EDL muscles from TNF-α-treated mice, neutrophil and macrophage concentrations were elevated seven- and threefold, respectively, compared with sham mice. Neutrophil and macrophage concentrations were also elevated five- and twofold, respectively, in solei of TNF-α- relative to sham-treated mice. Treatment with TNF-α elevated ubiquitin content by ∼25% relative to sham values for both the EDL and soleus muscles; however, these elevations were not statistically significant. No differences were observed between TNF-α- and sham-treated mice in body weight, food consumption, muscle mass, myofiber cross-sectional area, carbonyl groups, total protein content, or relative abundance of myosin heavy chain protein. Furthermore, no overt signs of muscle injury or regeneration were observed in muscles from TNF-α-treated mice in either the EDL or soleus muscles. These observations suggest that 7 days of TNF-α administration promote muscle inflammation as indicated by the accumulation of neutrophils and macrophages without overt signs of atrophy, injury, or regeneration.
Passive properties of the diaphragm in COPD
Authors: Moore Alastair J. , Stubbings Alison , Swallow Elisabeth B. , Dusmet Michael , Goldstraw Peter , Porcher Raphaël , Moxham John , Polkey Michael I. , Ferenczi Michael A.
Published: July 2006

Structural adaptations that occur in the diaphragm muscle of patients with chronic obstructive pulmonary disease (COPD), namely an increase in type I fibers and a decrease in type II fibers, have been explored in terms of the active contractile properties of the diaphragm. The aim of this study was to test the passive properties of the diaphragm by measuring the force response of relaxed diaphragm muscle fibers to stretching to determine the effect of COPD on these properties. Costal diaphragm biopsies were taken from patients with COPD and from controls with normal pulmonary function. From these biopsies, titin expression was assessed in diaphragm homogenates by gel electrophoresis, and the restoring force was measured by incremental stretching of single fibers in the relaxed state and measuring the force response to stretching. A quadratic model was used to illustrate the relationship between restoring force and muscle fiber length, and it revealed that COPD fibers generate significantly lower restoring forces than control fibers as judged by the area under the force-length curve. Furthermore, this finding applies to both type I and type II fibers. Gel electrophoresis revealed different titin isoforms in COPD and controls, consistent with the conclusion that COPD results not only in a change in muscle fiber-type distribution but in a structural change in the titin molecule in all muscle fiber types within the diaphragm. This may assist the muscle with the energetic changes in the length of the diaphragm required during breathing in COPD.
High-Resolution X-Ray Microtomography Is a Sensitive Method to Detect Vascular Calcification in Living Rats With Chronic Renal Failure
Authors: Persy Veerle , Postnov Andrei , Neven Ellen , Dams Geert , De Broe Marc , D’Haese Patrick , De Clerck Nora
Published: July 2006

Objective—

Chronic renal failure (CRF) is associated with a 10- to 20-fold increase in cardiovascular risk. Vascular calcification is a prominent feature of cardiovascular disease in patients with end-stage renal failure and contributes to the excess mortality in this population. In this study, we explored in vivo X-ray microtomography (micro-CT) as a tool to detect and follow-up vascular calcifications in the aorta of living rats with adenine-induced CRF.

Methods and Results—

With in vivo micro-CT, calcification of the aorta in uremic rats was clearly discernible on transversal virtual cross-sections. Micro-CT findings correlated well with tissue calcium content and histology. Repetitive scans in animals with light, moderate, and severe vascular calcification showed good reproducibility with minimal interference of motion artifacts. Moreover, both calcified volume and area could be quantified with this method.

Conclusions—

In vivo micro-CT scanning is a sensitive method to detect vascular calcifications in CRF rats, allowing follow-up and quantification of the development, and potential reversal during treatment, of vascular calcifications in living animals.
Interleukin-6 Induction of Protein S Is Regulated Through Signal Transducer and Activator of Transcription 3
Authors: de Wolf Cornelia J.F. , Cupers Rosemiek M.J. , Bertina Rogier M. , Vos Hans L.
Published: July 2006

Objective—The protein C anticoagulant pathway is an essential process for attenuating thrombin generation by the membrane-bound procoagulant complexes tenase and prothrombinase. In this pathway, protein S (PS) serves as a cofactor for activated protein C. PS circulates in plasma both in a free form and in complex with complement component 4b-binding protein (C4BP). C4BP is a known acute phase reactant, thereby suggesting a relation between PS and the acute phase response. Interleukin (IL)-6 has been shown to increase both PS and C4BP gene expression. Our objective was to study the regulation of PS gene expression by IL-6 in detail.

Methods and Results—IL-6 upregulates both PS mRNA and protein levels in liver-derived HepG2 cells. The promoter of the PS gene (PROS1) was cloned upstream from a luciferase reporter gene. After transfection in HepG2 cells, the luciferase activity was shown to be stimulated by the addition of IL-6. IL-6 exerts its effect through Signal Transducer and Activator of Transcription 3 (STAT3) that interacts with thePROS1promoter at a binding site in between nucleotides 229 to 207 upstream from the translational start.

Conclusion—IL-6 induces PS expression via STAT3. A possible function for IL-6–induced PS expression in cell survival is discussed.
ADAM17 Mediates Epidermal Growth Factor Receptor Transactivation and Vascular Smooth Muscle Cell Hypertrophy Induced by Angiotensin II
Authors: Ohtsu Haruhiko , Dempsey Peter J. , Frank Gerald D. , Brailoiu Eugen , Higuchi Sadaharu , Suzuki Hiroyuki , Nakashima Hidekatsu , Eguchi Kunie , Eguchi Satoru
Published: July 2006

Background—Angiotensin II (Ang II) promotes growth of vascular smooth muscle cells (VSMCs) via epidermal growth factor (EGF) receptor (EGFR) transactivation mediated through a metalloprotease-dependent shedding of heparin-binding EGF-like growth factor (HB-EGF). However, the identity of the metalloprotease responsible for this process remains unknown.

Methods and Results—To identify the metalloprotease required for Ang II-induced EGFR transactivation, primary cultured aortic VSMCs were infected with retrovirus encoding dominant negative (dn) mutant of ADAM10 or ADAM17. EGFR transactivation induced by Ang II was inhibited in VSMCs infected with dnADAM17 retrovirus but not with dnADAM10 retrovirus. However, Ang II comparably stimulated intracellular Ca2+elevation and JAK2 tyrosine phosphorylation in these VSMCs. In addition, dnADAM17 inhibited HB-EGF shedding induced by Ang II in A10 VSMCs expressing the AT1receptor. Moreover, Ang II enhanced protein synthesis and cell volume in VSMCs infected with control retrovirus, but not in VSMCs infected with dnADAM17 retrovirus.

Conclusion—ADAM17 activated by the AT1receptor is responsible for EGFR transactivation and subsequent protein synthesis in VSMCs. These findings demonstrate a previously missing molecular mechanism by which Ang II promotes vascular remodeling.
Protection of Human Vascular Smooth Muscle Cells From H
2
O
2
-Induced Apoptosis Through Functional Codependence Between HO-1 and AKT
Authors: Brunt Keith R. , Fenrich Keith K. , Kiani Gholam , Yat Tse M. , Pang Stephen C. , Ward Christopher A. , Melo Luis G.
Published: July 2006

Objective—

Oxidative stress (OS) induces smooth muscle cell apoptosis in the atherosclerotic plaque, leading to plaque instability and rupture. Heme oxygenase-1 (HO-1) exerts cytoprotective effects in the vessel wall. Recent evidence suggests that PKB/Akt may modulate HO-1 activity. This study examined the role of Akt in mediating the cytoprotective effects of HO-1 in OS-induced apoptosis of human aortic smooth muscle cells (HASMCs).

Methods and Results—

HASMCs were transduced with retroviral vectors expressing HO-1, Akt, or GFP and exposed to H
2
O
2
. Cell viability was assessed by MTT assay. OS was determined by CM-H2DCFDA fluorescence, and apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), caspase-3 activity, and Bcl-2/Bad levels. Mitochondrial membrane potential (ΔΨ
m
) was assessed by fluorescence-activated cell sorter (FACS) using JC-1. HO-1 reduced H
2
O
2
-induced OS and apoptosis. Akt knockdown removed the protective effect of HO-1 on ΔΨ
m
during exposure to H
2
O
2
. Conversely, HO-1 knockdown removed the protective effect of Akt on ΔΨ
m
. Inhibition of PI3K-Akt reduced induction of HO-1 protein expression by H
2
O
2
and blocked its anti-apoptotic effects. The Akt-mediated upregulation of HO-1 was dependent on activation of HO-1 promoter by Nrf2.

Conclusion—

HO-1 and Akt exert codependent cytoprotective effects against OS-induced apoptosis in HASMCs. These findings may have implications for the design of novel therapeutic strategies for plaque stabilization.
Osteoprotegerin Inactivation Accelerates Advanced Atherosclerotic Lesion Progression and Calcification in Older ApoE
−/−
Mice
Authors: Bennett Brian J. , Scatena Marta , Kirk Elizabeth A. , Rattazzi Marcello , Varon Rebecca M. , Averill Michelle , Schwartz Stephen M. , Giachelli Cecilia M. , Rosenfeld Michael E.
Published: July 2006

Objective—

Osteoprotegerin (OPG), a member of the tumor necrosis factor (TNF) superfamily of proteins, plays an important role in bone remodeling and is expressed in both mouse and human atherosclerotic lesions. The current study was designed to assess whether OPG plays a role in the progression and calcification of advanced atherosclerotic lesions in apoE
−/−
mice.

Methods and Results—

Atherosclerotic lesion area and composition and aortic calcium content were examined in mice deficient in both OPG and apolipoprotein E (
OPG
−/−
.apoE
−/−
mice) at 20, 40, and 60 weeks of age. Littermate
OPG
+/+
.apoE
−/−
mice were used as controls. The average cross-sectional area of lesions in the innominate arteries was increased in OPG
−/−
.apoE
−/−
mice at 40 and 60 weeks of age. The increase in lesion area was coupled with a reduced cellularity and an increase in connective tissue including laminated layers of elastin. Sixty-week-old OPG
−/−
.apoE
−/−
mice also had an increase in the area of calcification of the lesions. There were no differences in markers of plaque stability. In vitro, OPG induced matrix metalloproteinase-9 (MMP-9) activity in macrophages and smooth muscle cells and acted as a survival factor for serum-deprived smooth muscle cells.

Conclusion—

OPG inhibits advanced plaque progression by preventing an increase in lesion size and lesion calcification. OPG may act as a survival factor and may modulate MMP9 production in vascular cells.
Akt Promotes Increased Cardiomyocyte Cycling and Expansion of the Cardiac Progenitor Cell Population
Authors: Gude Natalie , Muraski John , Rubio Marta , Kajstura Jan , Schaefer Erik , Anversa Piero , Sussman Mark A.
Published: July 2006

Activation of Akt is associated with enhanced cell cycling and cellular proliferation in nonmyocytes, but this effect of nuclear Akt accumulation has not been explored in the context of the myocardium. Cardiac-specific expression of nuclear-targeted Akt (Akt/nuc) in transgenics prolongs postnatal cell cycling as evidenced by increased numbers of Ki67
+
cardiomyocytes at 2 to 3 weeks after birth. Similarly, nuclear-targeting of Akt promotes expansion of the presumptive cardiac progenitor cell population as assessed by immunolabeling for c-kit in combination with myocyte-specific markers Nkx 2.5 or MEF 2C. Increases in pro-proliferative cytokines, including tumor-necrosis superfamily 8, interleukin-17e, and hepatocyte growth factor, were found in nuclear-targeted Akt myocardial samples. Concurrent signaling mediated by paracrine factors downstream of Akt/nuc expression may be responsible for phenotypic effects of nuclear-targeted Akt in the myocardium, including enhanced cell proliferation and expansion of the stem cell population.
Endoglin Regulates Cyclooxygenase-2 Expression and Activity
Authors: Jerkic Mirjana , Rivas-Elena Juan V. , Santibanez Juan F. , Prieto Marta , Rodríguez-Barbero Alicia , Perez-Barriocanal Fernando , Pericacho Miguel , Arévalo Miguel , Vary Calvin P.H. , Letarte Michelle , Bernabeu Carmelo , López-Novoa Jose M.
Published: July 2006

The endoglin heterozygous (
Eng
+/−
) mouse, which serves as a model of hereditary hemorrhagic telangiectasia (HHT), was shown to express reduced levels of endothelial NO synthase (eNOS) with impaired activity. Because of intricate changes in vasomotor function in the
Eng
+/−
mice and the potential interactions between the NO- and prostaglandin-producing pathways, we assessed the expression and function of cyclooxygenase (COX) isoforms. A specific upregulation of COX-2 in the vascular endothelium and increased urinary excretion of prostaglandin E
2
were observed in the
Eng
+/−
mice. Specific COX-2 inhibition with parecoxib transiently increased arterial pressure in
Eng
+/−
but not in
Eng
+/+
mice. Transfection of endoglin in L6E9 myoblasts, shown previously to stimulate eNOS expression, led to downregulation of COX-2 with no change in COX-1. In addition, COX-2 promoter activity and protein levels were inversely correlated with endoglin levels, in doxycyclin-inducible endothelial cells. Chronic NO synthesis inhibition with
N
ω
-nitro-
l
-arginine methyl ester induced a marked increase in COX-2 only in the normal
Eng
+/+
mice.
N
ω
-nitro-
l
-arginine methyl ester also increased COX-2 expression and promoter activity in doxycyclin-inducible endoglin expressing endothelial cells, but not in control cells. The level of COX-2 expression following transforming growth factor-β1 treatment was less in endoglin than in mock transfected L6E9 myoblasts and was higher in human endothelial cells silenced for endoglin expression. Our results indicate that endoglin is involved in the regulation of COX-2 activity. Furthermore, reduced endoglin levels and associated impaired NO production may be responsible, at least in part, for augmented COX-2 expression and activity in the
Eng
+/−
mice.
Hypoxia Regulates Bone Morphogenetic Protein Signaling Through C-Terminal–Binding Protein 1
Authors: Wu Xinqi , Chang Mun Seog , Mitsialis S. Alex , Kourembanas Stella
Published: July 2006

Bone morphogenetic protein receptor 2 (BMPR2) mutations have been linked to familial pulmonary arterial hypertension (PAH), but the molecular pathways leading to this severe pathology remain poorly characterized. We report that hypoxia, a paramount stimulus for the development of pulmonary hypertension, suppresses the expression of inhibitor of differentiation 1 (Id1), a downstream target of the BMPR2 pathway, in human pulmonary artery smooth muscle cells (HPASMC). This attenuation of BMP signaling by hypoxia is conveyed through a repression of the transcriptional activity of the BMP responsive element (BRE) through mechanisms involving the transcriptional corepressor C-terminal–binding protein 1 (CtBP-1) and histone deacetylases (HDACs). Concordantly, overexpression of CtBP-1 suppressed BMP signaling, whereas small interfering RNA against CtBP-1 efficiently enhanced BMP stimulation of Id1 gene expression. Scavengers of reactive oxygen species had no effect on the hypoxic regulation of Id1, but, significantly, enhancement of the intracellular NADH/NAD
+
ratio mimicked the effects of hypoxia. These results indicate that attenuation of BMP signaling can occur through modulation of CtBP-1 activity by hypoxia-induced changes in the NADH/NAD
+
ratio. Our findings, taken in context with the observed prevalence of pulmonary arterial hypertension associated with BMPR2 mutations, define converging molecular pathways that lead to the development of pulmonary hypertension, through either genetic or epigenetic loss of function of components of the BMP signaling pathway.
Novel Role for Integrin-Linked Kinase in Modulation of Coxsackievirus B3 Replication and Virus-Induced Cardiomyocyte Injury
Authors: Esfandiarei Mitra , Suarez Agripina , Amaral Ansel , Si Xiaoning , Rahmani Maziar , Dedhar Shoukat , McManus Bruce M.
Published: July 2006

Viral myocarditis is a major cause of sudden cardiac death in children and young adults. Among viruses, coxsackievirus B3 (CVB3) is the most common agent for myocarditis. Recently, more consideration has been given to the role of signaling pathways in pathogenesis of enteroviral myocarditis, providing new platform for identifying a new potential therapeutic target for this, so far, incurable disease. Previously, we reported on the role of the protein kinase-B/Akt in CVB3 replication and virus-induced cell injury. Here, we report on regulation of virus-induced Akt activation by the integrin-linked kinase in infected mouse cardiomyocytes and HeLa cells. This study also presents the first observation that inhibition of ILK in CVB3-infected cells significantly improves the viability of infected cells, while blocking viral replication and virus release. Complementary experiments using a constitutively active form of Akt1 revealed that the observed protective effect of ILK inhibition is dependent on the associated downregulation of virus-induced Akt activation. To our knowledge, this is the first report of such beneficial effects of ILK inhibition in a viral infection model and conveys new insights in our efforts to characterize a novel therapeutic target for treatment of enteroviral myocarditis.
An fMRI Analysis of the Human Hippocampus: Inference, Context, and Task Awareness
Authors: Greene Anthony J. , Gross William L. , Elsinger Catherine L. , Rao Stephen M.
Published: July 2006

The hippocampus is critical for encoding and retrieving semantic and episodic memories. Animal studies indicate that the hippocampus is also required for relational learning tasks. A prototypical relational learning task, and the one investigated in this experiment, using event-related functional magnetic resonance imaging, is the transitive inference (TI) task. In the TI task, participants were to choose between A and B (A?B) and learned by trial and error to choose A (A > B). There were four such premise pairs during a training (A > B, B > C, C > D, D > E). These can be acquired distinctly or can be organized into a superordinate hierarchy (A > B > C > D > E), which would efficiently represent all the learned relations and allow inferences (e.g., B > D). At test there was no reinforcement: In addition to premise pairs, untrained pairings were introduced (e.g., A?E, B?D). Correctly inferring that B > D is taken as evidence for the formation of a superordinate hierarchy; several alternatives to the superordinate hierarchy hypothesis are considered. Awareness of the formation of this hierarchy was measured by a postscan questionnaire. Four main findings are reported: (1) Inferential performance and task awareness dissociated behaviorally and at the level of hemodynamic response; (2) As expected, performance on the inferred relation, B > D, corresponded to the ability to simultaneously acquire B > C and C > D premise pairs during training; (3) Interestingly, acquiring these “inner pairs” corresponded to greater hippocampal activation than the “outer pairs” (A > B, D > E) for all participants. However, a distinct pattern of hippocampal activity for these inner pairs differentiated those able to perform the inferential discrimination, B > D, at test. Because these inner premise pairs require contextual discrimination (e.g., C is incorrect in the context of B but correct in the context of D), we argue that the TI task is hippocampal-dependent because the premise pair acquisition necessary for inference is hippocampal-dependent; (4) We found B > D related hippocampal activity at test that is anatomically consistent with preconsolidation recall effects shown in other studies.
Hurricane Juan (2003). Part I: A Diagnostic and Compositing Life Cycle Study
Authors: McTaggart-Cowan Ron , Atallah Eyad H. , Gyakum John R. , Bosart Lance F.
Published: July 2006

A detailed analysis of the complex life cycle of Hurricane Juan (in 2003) is undertaken to elucidate the structures and forcings that prevailed over the period leading up to the hurricane’s landfall in Halifax, Nova Scotia, Canada. Despite the presence of easterly wave precursors, Hurricane Juan’s initial development is shown to occur in a baroclinic environment beneath a low-latitude potential vorticity streamer. This feature interacts with a lower-level shear line as the incipient vortex begins to effectively focus ascent and convection. The system undergoes a slow tropical transition over a period of several days as the deep-layer shear over the developing storm decreases. The hurricane is repeatedly perturbed by subsynoptic-scale waves traveling along the leading edge of a large upstream trough. However, Hurricane Juan maintains its tropical structure despite its relatively high formation latitude (28°N) and its northward trajectory. The unusual persistence of the storm’s tropical nature as it propagates northward is of primary interest in this study. In particular, the role of persistent ridging along the east coast of North America is investigated both in high-resolution analyses for Hurricane Juan and in a compositing framework. Dynamic tropopause, quasigeostrophic, and modified Eady model diagnostics are used to elucidate the interactions between Hurricane Juan and this amplified midlatitude flow. Given the strength and persistence of the anomalous ridge–trough couplet both in the case diagnosis and in the composite fields, the study concludes that the presence of prestorm, high-amplitude ridging along the east coast likely reinforced by diabatic ridging downshear of the storm itself produces an environment both dynamically and thermodynamically conducive to the high-latitude landfall of hurricanes still in the tropical phase.
Object-Based Verification of Precipitation Forecasts. Part I: Methodology and Application to Mesoscale Rain Areas
Authors: Davis Christopher , Brown Barbara , Bullock Randy
Published: July 2006

A recently developed method of defining rain areas for the purpose of verifying precipitation produced by numerical weather prediction models is described. Precipitation objects are defined in both forecasts and observations based on a convolution (smoothing) and thresholding procedure. In an application of the new verification approach, the forecasts produced by the Weather Research and Forecasting (WRF) model are evaluated on a 22-km grid covering the continental United States during July–August 2001. Observed rainfall is derived from the stage-IV product from NCEP on a 4-km grid (averaged to a 22-km grid). It is found that the WRF produces too many large rain areas, and the spatial and temporal distribution of the rain areas reveals regional underestimates of the diurnal cycle in rain-area occurrence frequency. Objects in the two datasets are then matched according to the separation distance of their centroids. Overall, WRF rain errors exhibit no large biases in location, but do suffer from a positive size bias that maximizes during the later afternoon. This coincides with an excessive narrowing of the rainfall intensity range, consistent with the dominance of parameterized convection. Finally, matching ability has a strong dependence on object size and is interpreted as the influence of relatively predictable synoptic-scale systems on the larger areas.