bluuebunny/crossref_metadata_2025 huggingface dataset:
Estradiol-induced expression of Na+-K+-ATPase catalytic isoforms in rat arteries: gender differences in activity mediated by nitric oxide donors
Authors: Palacios Javier , Marusic Elisa T. , Lopez Nandy C. , Gonzalez Magdalena , Michea Luis
Published: April 2004

We tested the hypothesis that previously demonstrated gender differences in ACh-induced vascular relaxation could involve diverse Na+-K+-ATPase functions. We determined Na+-K+-ATPase by measuring arterial ouabain-sensitive86Rb uptake in response to ACh. We found a significant increase of Na+pump activity only in aortic rings from female rats (control 206 ± 11 vs. 367 ± 29 nmol86Rb/K·min–1·g wt tissue–1; P < 0.01). Ovariectomy eliminated sex differences in Na+-K+-ATPase function, and chronic in vivo hormone replacement with 17β-estradiol restored the ACh effect on Na+-K+-ATPase. Because ACh acts by enhancing production of NO, we examined whether the NO donor sodium nitroprusside (SNP) mimics the action of ACh on Na+-K+-ATPase activity. SNP increased ouabain-sensitive86Rb uptake in denuded female arteries (control 123 ± 7 vs. 197 ± 12 nmol86Rb/K·min–1·g wt tissue–1; P < 0.05). Methylene blue (an inhibitor of guanylate cyclase) and KT-5823 (a cGMP-dependent kinase inhibitor) blocked the stimulatory action of SNP. Exposure of female thoracic aorta to the Na+/K+pump inhibitor ouabain significantly decreased SNP-induced and ACh-mediated relaxation of aortic rings. At the molecular level, Western blot analysis of arterial tissue revealed significant gender differences in the relative abundance of catalytic isoforms of Na+-K+-ATPase. Female-derived aortas exhibited a greater proportion of α2-isoform (44%) compared with male-derived aortas. Furthermore, estradiol upregulated the expression of α2mRNA in male arterial explants. Our results demonstrate that enhancement of ACh-induced relaxation observed in female rats may be in part explained by 1) NO-dependent increased Na+-K+-ATPase activity in female vascular tissue and 2) greater abundance of Na+-K+-ATPase α2-isoform in females.
Leukocyte dependence of platelet adhesion in postcapillary venules
Authors: Cooper Dianne , Russell Janice , Chitman Keith D. , Williams Matthew C. , Wolf Robert E. , Granger D. Neil
Published: April 2004

Reperfusion of ischemic tissues results in development of a proinflammatory, prothrombogenic phenotype, culminating in the recruitment of leukocytes and platelets within postcapillary venules. Recent studies have indicated an interdependence of platelet and leukocyte adhesion, suggesting that heterotypic blood cell interactions may account for postischemic platelet recruitment. The objectives of this study were to 1) determine whether ischemia-reperfusion (I/R)-induced platelet recruitment is leukocyte dependent and 2) quantify the contributions of leukocytes and endothelial cells in this platelet recruitment. Intravital microscopy was used to monitor the recruitment of fluorescently labeled platelets in postcapillary venules of the small intestine after 45-min ischemia and 4-h reperfusion. To assess the leukocyte dependence of platelet adhesion, platelets from wild-type mice were infused into mice deficient in neutrophils and/or lymphocytes and mice deficient in key leukocyte adhesion molecules (CD18 and ICAM-1). These antileukocyte strategies resulted in significantly reduced platelet recruitment. Simultaneous visualization of platelets and leukocytes enabled quantification of leukocyte-dependent and endothelium-dependent platelet adhesion. It was observed that in wild-type animals 74% of I/R-induced platelet adhesion was a result of platelet-leukocyte interactions. Although the majority of adherent platelets were associated with leukocytes, <50% of adherent leukocytes were platelet bearing, suggesting that not all adherent leukocytes support platelet adhesion. These results are consistent with leukocytes playing a major role in supporting I/R-induced platelet adhesion.
Effect of fitness on arm vascular and metabolic responses to upper body exercise
Authors: Volianitis S. , Yoshiga C. C. , Nissen P. , Secher N. H.
Published: April 2004

We investigated arm perfusion and metabolism during upper body exercise. Eight average, fit subjects and seven rowers, mean ± SE maximal oxygen uptake (V̇o2 max) 157 ± 7 and 223 ± 14 ml O2· kg–0.73·min–1, respectively, performed incremental arm cranking to exhaustion. Arm blood flow (ABF) was measured with thermodilution and arm muscle mass was estimated by dual-energy X-ray absorptiometry. During maximal arm cranking, pulmonary V̇o2 was ∼45% higher in the rowers compared with the untrained subjects and peak ABF was 6.44 ± 0.40 and 4.55 ± 0.26 l/min, respectively ( P < 0.05). The arm muscle mass for the rowers and the untrained subjects was 3.5 ± 0.4 and 3.3 ± 0.1 kg, i.e., arm perfusion was 1.9 ± 0.2 and 1.4 ± 0.1 l blood·kg–1·min–1, respectively ( P < 0.05). The arteriovenous O2 difference was 156 ± 7 and 120 ± 8 ml/l, respectively, and arm V̇o2 was 0.98 ± 0.08 and 0.60 ± 0.04 l/min corresponding with 281 ± 22 and 181 ± 12 ml/kg, while arm O2 diffusional conductance was 49.9 ± 4.3 and 18.6 ± 3.2 ml·min–1·mmHg–1, respectively ( P < 0.05). Also, lactate release in the rowers was almost three times higher than in the untrained subjects (26.4 ± 1.1 vs. 9.5 ± 0.4 mmol/min, P < 0.05). The energy requirement of an ∼50% larger arm work capacity after long-term arm endurance training is covered by an ∼60% increase in aerobic metabolism and an almost tripling of the anaerobic capacity.
Excitatory amino acids in rostral ventrolateral medulla support blood pressure during water deprivation in rats
Authors: Brooks Virginia L. , Freeman Korrina L. , Clow Kathy A.
Published: April 2004

Water deprivation is associated with regional increases in sympathetic tone, but whether this is mediated by changes in brain stem regulation of sympathetic activity is unknown. Therefore, this study tested the hypothesis that water deprivation increases excitatory amino acid (EAA) drive of the rostral ventrolateral medulla (RVLM), by determining whether bilateral microinjection of kynurenate (Kyn; 2.7 nmol) into the RVLM decreases arterial pressure more in water-deprived than water-replete rats. Plasma osmolality was increased in 48-h water-deprived rats (313 ± 1 mosmol/kgH2O; P < 0.05) compared with 24-h water-deprived rats (306 ± 2 mosmol/kgH2O) and water-replete animals (300 ± 2 mosmol/kgH2O). Kyn decreased arterial pressure by 28.1 ± 5.2 mmHg ( P < 0.01) in 48-h water-deprived rats but had no effect in water-replete rats (–5.9 ± 1.3 mmHg). Variable depressor effects were observed in 24-h water-deprived animals (–12.5 ± 2.4 mmHg, not significant); however, in all rats the Kyn depressor response was strongly correlated to the osmolality level ( P < 0.01; r2 = 0.47). The pressor responses to unilateral microinjection of increasing doses (0.1, 0.5, 1.0, and 5.0 nmol) of glutamate were enhanced ( P < 0.05) during water deprivation, but the pressor responses to intravenous phenylephrine injection were smaller ( P < 0.05). These data suggest that water deprivation increases EAA drive to the RVLM, in part by increasing responsiveness of the RVLM to EAA such as glutamate.
Developmental differences in L-type calcium current of human atrial myocytes
Authors: Tipparaju Srinivas M. , Kumar Rajiv , Wang Yanggan , Joyner Ronald W. , Wagner Mary B.
Published: April 2004

We investigated differences in L-type Ca2+ current ( ICa) between infant (INF, 1–12 mo old), young adult (YAD, 14–18 yr old), and older adult (AD) myocytes from biopsies of right atrial appendages. Basal ICa was smaller in INF myocytes (1.2 ± 0.1 pA/pF, n = 29, 6 ± 1 mo old, 11 patients) than in YAD (2.5 ± 0.2 pA/pF, n = 20, 16 ± 1 yr old, 5 patients) or AD (2.6 ± 0.3 pA/pF, n = 19, 66 ± 3 yr old, 9 patients) myocytes ( P < 0.05). Maximal ICa produced by isoproterenol (Iso) was similar in INF, YAD, and AD cells: 8.4 ± 1.1, 9.6 ± 1.0, and 9.2 ± 1.3 pA/pF, respectively. Efficacy (Emax) was larger in INF (607 ± 50%) than for YAD (371 ± 29%) or AD (455 ± 12%) myocytes. Potency (EC50) was 8- to 10-fold higher in AD (0.82 ± 0.09 nM) or YAD (0.41 ± 0.14 nM) than in INF (7.6 ± 3.5 nM) myocytes. Protein levels were similar for Giα2 but much greater for Giα3 in INF than in AD or YAD atrial tissue. When Giα3 activity was inhibited by inclusion of a Giα3 COOH-terminal decapeptide in the pipette, basal ICa and the response to 10 nM Iso were increased in INF, but not in YAD, cells. We propose that basal ICa and the response to low-dose β-adrenergic stimulation are inhibited in INF (but not YAD or AD) cells as a result of constitutive inhibitory effects of Giα3.
Myocardial ischemia-reperfusion injury is enhanced in a model of systemic allergy and asthma
Authors: Hazarika Surovi , Van Scott Michael R. , Lust Robert M.
Published: April 2004

Despite epidemiological evidence of cardiovascular complications in asthmatics, the direct contribution of asthmatic pathophysiology to cardiovascular effects is unknown. Considering parallels in underlying pathophysiology, we tested the hypothesis that presence of systemic allergy and asthma worsens the outcome of myocardial ischemia-reperfusion injury. Systemic allergy and asthma were created in rabbits by repeated intraperitoneal injections of allergen with adjuvant, followed by an airway challenge in two groups. Nonsensitized animals served as controls. In situ myocardial ischemia-reperfusion was induced in anesthetized animals by a 30-min ligation of a coronary artery, followed by 3 h of reperfusion. Ischemia-reperfusion was done at 24 h after intraperitoneal boost (1 DB) and 7 days (7 DB) after the last intraperitoneal injection and at 24 h (1DAWCH) and 7 days (7DAWCH) after airway challenge. The infarct size (determined by 2,3,5-triphenyltetrazolium chloride staining, normalized to area at risk) was significantly higher in all sensitized groups compared with control (1DB, 31 ± 4; 7DB, 28.9 ± 2.6; 1DAWCH, 66.1 ± 4.1; 7DAWCH, 28.9 ± 9.2; control, 16.7 ± 3.2; means ± SE; P < 0.01 by ANOVA; n = 6). The 1DAWCH group showed significantly greater infarct than all other groups ( P < 0.05). Myocardial neutrophil infiltration was significantly higher in the sensitized groups compared with control ( P < 0.01). Tissue neutrophil counts showed a strong positive correlation to infarct sizes ( r2= 0.9). These observations indicate that the presence of systemic allergy and asthma is associated with increased myocardial neutrophil infiltration during acute ischemia-reperfusion and increased size of the resulting infarct.
Regulation of rat pial arteriolar smooth muscle relaxation in vivo through multidrug resistance protein 5-mediated cGMP efflux
Authors: Xu Hao-Liang , Gavrilyuk Vitaliy , Wolde Hailemariam M. , Baughman Verna L. , Pelligrino Dale A.
Published: April 2004

Multidrug resistance protein 5 (MRP5) has been linked to cGMP cellular export in peripheral vascular smooth muscle cells (VSMCs) and is widely expressed in brain vascular tissue. In the present study, we examined whether knockdown of MRP5 in pial arterioles [via antisense oligodeoxynucleotide (ODN) applications] affected nitric oxide (NO)/cGMP-induced dilations. The antisense or (as a control) missense ODN was applied to the cortical surface ∼24 h before study via closed cranial windows. The efficacy of the antisense vs. missense ODN in eliciting selective reductions in MRP5 expression was confirmed by analysis of MRP5 mRNA in pial tissue. Unexpectedly, in initial studies, a significantly lower maximal pial arteriolar diameter increase in the presence of the NO donor S-nitrosoacetylpenicillamine (SNAP) was seen in the antisense vs. missense ODN-treated rats (35 vs. 48% diameter increase, respectively). It was suspected that this related to a reduced vascular smooth muscle cell sensitivity to cGMP due to prolonged exposure to increased intracellular cGMP levels elevated by overnight restriction of cGMP efflux. That postulate was supported by a finding of a diminished vasodilating response to the cGMP-dependent protein kinase-activating cGMP analog 8- p-chlorophenylthio-cGMP in antisense vs. missense ODN-treated rats. To prevent desensitization, additional rats were studied in the presence of chronic NOS inhibition via Nω-nitro-l-arginine. In the NO synthase (NOS)-inhibited rats, the maximal SNAP response was much higher in the antisense (62% increase) vs. the missense ODN (40% increase) group. A similar result was obtained when monitoring responses to the soluble guanylyl cyclase-activating drugs YC-1 and BAY 41–2272. Moreover, in the presence of NOS inhibition, the normal SNAP-induced rise in periarachnoid cerebrospinal fluid cGMP levels, which reflects cGMP efflux, was absent in the antisense ODN-treated rats, a finding consistent with loss of MRP5 function. In conclusion, if one minimizes the confounding effects of basal cGMP production, a clearer picture emerges, one that indicates an important role for MRP5-mediated cGMP efflux in the regulation of NO-induced cerebral arteriolar relaxation.
Endothelium-derived microparticles impair endothelial function in vitro
Authors: Brodsky Sergey V. , Zhang Fan , Nasjletti Alberto , Goligorsky Michael S.
Published: April 2004

Endothelial cell dysfunction (ECD) is emerging as the common denominator for diverse and highly prevalent cardiovascular diseases. Recently, an increased number of procoagulant circulating endothelial microparticles (EMPs) has been identified in patients with acute myocardial ischemia, preeclampsia, and diabetes, which suggests that these particles represent a surrogate marker of ECD. Our previous studies showed procoagulant potential of endothelial microparticles and mobilization of microparticles by PAI-1. The aim of this study was to test the effects of isolated EMPs on the vascular endothelium. EMPs impaired ACh-induced vasorelaxation and nitric oxide production by aortic rings obtained from Sprague-Dawley rats in a concentration-dependent manner. This effect was accompanied by increased superoxide production by aortic rings and cultured endothelial cells that were coincubated with EMPs and was inhibited by a SOD mimetic and blunted by an endothelial nitric oxide synthase inhibitor. Superoxide was also produced by isolated EMP. In addition, p22(phox) subunit of NADPH-oxidase was detected in EMP. Our data strongly suggest that circulating EMPs directly affect the endothelium and thus not only act as a marker for ECD but also aggravate preexisting ECD.
The AV junction region of the heart: a comprehensive study correlating gross anatomy and direct three-dimensional analysis. Part II. Morphology and cytoarchitecture
Authors: Racker Darlene K.
Published: April 2004

This “Part II morphology and cytoarchitecture” study is based on paraffin-embedded specimens in which the extracellular and intracellular matrix are preserved; single parallel, perpendicular, and transverse serial sections of the entire atrioventricular (AV) junction region (AVJR) and their correlation with photographs of the tissue blocks. As in Part I, the same major new findings are: 1) a coronary sinus fossa is formed by the superoposterior right medial atria wall (MAW), the left atrium, and the coronary sinus roof; 2) the posterior MAW forms two myocardial bridges and is isolated from the sinus venarum by the floor of the inferior vena cava; 3) the tendon of Todaro terminates in the superior lip of the coronary sinus ostium; 4) only ordinary myocardium contacts the annulus fibrosus, and there is little to no collagen separating its myofibers and tissues; 5) the ventricular septum shoulder is humped shaped, completely overlaid by annular myocardium, and joined by struts of papillary muscle; 6) the membranous septum joining the ventricular septum shoulder to the crista supraventricularis forms part of the aortic valve sinus walls; and 7) myocardium of the atrionodal bundles is aggregated into numerous small fascicles encased by collagen and is outside of the MAW as are the other specialized tissues. The proximal AV bundle and medial atrionodal bundle are aligned to the medial leg of Koch's triangle and the tendon of Todaro. These data show, therefore, that the AVJR contains two overlapping atrial circuits. In the MAW, acivation of the posterior region is delayed because of the two myocardial bridges. Puncture of the AVJR can produce communication with an extracardiac space, posteriorly and medially, and with the aorta, anteriorly.
Dihydropyridine and ryanodine receptor binding after eccentric contractions in mouse skeletal muscle
Authors: Ingalls Christopher P. , Warren Gordon L. , Zhang Jia-Zheng , Hamilton Susan L. , Armstrong R. B.
Published: April 2004

The purpose of this study was to determine whether there are alterations in the dihydropyridine and/or ryanodine receptors that might explain the excitation-contraction uncoupling associated with eccentric contraction-induced skeletal muscle injury. The left anterior crural muscles (i.e., tibialis anterior, extensor digitorum longus, and extensor hallucis longus) of mice were injured in vivo by 150 eccentric contractions. Peak isometric tetanic torque of the anterior crural muscles was reduced ∼45% immediately and 3 days after the eccentric contractions. Partial restoration of peak isometric tetanic and subtetanic forces of injured extensor digitorum longus muscles by 10 mM caffeine indicated the presence of excitation-contraction uncoupling. Scatchard analysis of [3H]ryanodine binding indicated that the number of ryanodine receptor binding sites was not altered immediately postinjury but decreased 16% 3 days later. Dihydropyridine receptor binding sites increased ∼20% immediately after and were elevated to the same extent 3 days after the injury protocol. Muscle injury did not alter the sensitivity of either receptor. These data suggest that a loss or altered sensitivity of the dihydropyridine and ryanodine receptors does not contribute to the excitation-contraction uncoupling immediately after contraction-induced muscle injury. We also concluded that the loss in ryanodine receptors 3 days after injury is not the primary cause of excitation-contraction uncoupling at that time.
Optimal hemoglobin concentration and high altitude: a theoretical approach for Andean men at rest
Authors: Villafuerte Francisco C. , Cárdenas Rosa , Monge-C Carlos
Published: April 2004

The beneficial role of erythrocytosis for O2 transport has been questioned by evidence from bloodletting and hemodilution research as well as by studies suggesting the existence of an “optimal” hematocrit (Hct) or hemoglobin concentration ([Hb]) value. To assess to what extent erythrocytosis is beneficial in Andean men at high altitude, we examined and discussed optimal [Hb] using a mathematical approach by modeling the mixed (mean) venous Po2 (Pv̄O2) and arterial O2 content, considering for both the relation between [Hb] and arterial Po2. Relations of [Hb] to other physiological variables such as cardiac output and convective arterial O2 transport were also discussed, revealing the importance of Pv̄O2 in this model. Our theoretical analysis suggests that increasing [Hb] allows increase and maintenance of Pv̄O2 with only moderate declines in arterial Po2 as a consequence of moderate increases in altitude, reaching its maximum at the optimal [Hb] of 14.7 g/dl. Our analysis also shows that [Hb] corresponding to high arterial O2 content and O2 transport values is apparently not quite advantageous for improvement of oxygenation. Furthermore, chronic mountain sickness is discussed as an insightful example of the effects of excessive erythrocytosis at high altitude.
Fluorescent microsphere method is suitable for chronic bone blood flow measurement: a long-term study after meniscectomy in rabbits
Authors: Anetzberger H. , Thein E. , Löffler G. , Messmer K.
Published: April 2004

The fluorescent microsphere (FM) method is considered a reliable technique to determine regional bone blood flow (RBBF) in acute experiments. In this study, we verified the accuracy and validity of this technique for measurement of RBBF in a long-term experiment and examined RBBF after meniscectomy. Twenty-four anesthetized female New Zealand white rabbits (3 groups, each n = 8) received consecutive left ventricular injections of FM in defined time intervals after meniscectomy: group 1 from preoperation to 3 wk postoperation; group 2 from 3 to 7 wk postoperation; and group 3 from 7 to 11 wk postoperation. To test the precision of the FM method, two FM species were injected simultaneously at the first and last measurement. After the experiment, humeri, femora, tibiae, and reference organs (kidney, lung, brain) were removed and dissected according to standardized protocols. Fluorescence was determined in each reference blood and tissue sample, and blood flow values were calculated. Blood flow in kidney, lung, and brain revealed no significant difference between right and left side and remained unchanged during the observation period, thus excluding errors due to shunting and dislodging of spheres in our experiments. Comparison of relative bone blood flow values obtained by simultaneously injected FM showed an excellent correlation at the first and last injection, indicating valid RBBF measurements in long-term experiments. We found a significant increase in RBBF 3 wk after meniscectomy in the right tibial condyles compared with the nonoperated left side. Similar changes were found in the femoral condyles. RBBF in other regions of tibia, femur, and humerus revealed no significant differences between right- and left-sided bone samples of the same region. Our results demonstrate that the FM method is valid for measuring RBBF in long-term experiments. In addition, we were able to demonstrate that meniscectomy leads to an increase in RBBF in the tibial condyles at a very early stage. This increase might be caused by stress-induced alterations of the subchondral bone.
Resistance training enhances components of the insulin signaling cascade in normal and high-fat-fed rodent skeletal muscle
Authors: Krisan Adam D. , Collins Dale E. , Crain Andrew M. , Kwong Connie C. , Singh Mohenish K. , Bernard Jeffrey R. , Yaspelkis Ben B.
Published: April 2004

Our laboratory recently reported that chronic resistance training (RT) improved insulin-stimulated glucose transport in normal rodent skeletal muscle, owing, in part, to increased GLUT-4 protein concentration (Yaspelkis BB III, Singh MK, Trevino B, Krisan AD, and Collins DE. Acta Physiol Scand 175: 315-323, 2002). However, it remained to be determined whether these improvements resulted from alterations in the insulin signaling cascade as well. In addition, the possibility existed that RT might improve skeletal muscle insulin resistance. Thirty-two male Sprague-Dawley rats were assigned to four groups: control diet (Con)-sedentary (Sed); Con-RT; high-fat diet (HF)-Sed; and HF-RT. Animals consumed their respective diets for 9 wk; then RT animals performed 12 wk of training (3 sets, 10 repetitions at 75% one-repetition maximum, 3×/wk). Animals remained on their dietary treatments over the 12-wk period. After the training period, animals were subjected to hindlimb perfusions. Insulin-stimulated insulin receptor substrate-1-associated phosphatidylinositol-3 kinase activity was enhanced in the red gastrocnemius and quadriceps of Con-RT and HF-RT animals. Atypical PKC-ζ/λ and Akt activities were reduced in HF-Sed and normalized in HF-RT animals. Resistance training increased GLUT-4 protein concentration in red gastrocnemius and quadriceps of Con-RT and HF-RT animals. No differences were observed in total protein concentrations of insulin receptor substrate-1, Akt, atypical PKC-ζ/λ, or phosphorylation of Akt. Collectively, these findings suggest that resistance training increases insulin-stimulated carbohydrate metabolism in normal skeletal muscle and reverses high-fat diet-induced skeletal muscle insulin resistance by altering components of both the insulin signaling cascade and glucose transporter effector system.
Spinal reciprocal inhibition in human locomotion
Authors: Kido Aiko , Tanaka Naofumi , Stein Richard B.
Published: April 2004

The purpose of this paper was to study spinal inhibition during several different motor tasks in healthy human subjects. The short-latency, reciprocal inhibitory pathways from the common peroneal (CP) nerve to the soleus muscle and from the tibial nerve to the tibialis anterior muscle were studied as a depression of ongoing voluntary electromyograph (EMG) activity. First, the effect of stimulus intensity on the amount of inhibition was examined to decide an appropriate stimulation to study the task-dependent modulation of inhibition. Then, the inhibition at one level of stimulation (1.5 × motor threshold) was investigated during standing, walking, and running. The change in slope of inhibition vs. EMG level, which approximates the fraction of ongoing activity that is inhibited, decreased with CP stimulation from 0.52 during standing to 0.30 during fast walking (6 km/h) to 0.17 during running at 9 km/h. Similarly, the slope decreased with tibial nerve stimulation from 0.68 (standing) to 0.42 (fast walking) to 0.35 (running at 9 km/h). All differences, except the last one, were highly significant ( P < 0.01, Student's t-test). However, the difference between walking (0.42) and running (0.36) at the same speed (6 km/h) was not significant with tibial nerve stimulation and only significant at P < 0.05 with CP nerve stimulation (0.30, 0.20). Also, the difference between standing (0.52) and slow walking (3 km/h; 0.41) with CP stimulation was not significant, but it was significant ( P < 0.01) with tibial nerve stimulation (0.68, 0.49). In conclusion, our findings indicate that spinal reciprocal inhibition decreases substantially with increasing speed and only changes to a lesser extent with task.
Ionotropic excitatory amino acid receptors in pre-Bötzinger complex play a modulatory role in hypoxia-induced gasping in vivo
Authors: Solomon Irene C.
Published: April 2004

Activation of ionotropic excitatory amino acid (EAA) receptors in pre-Bötzinger complex (pre-BötC) not only influences the eupneic pattern of phrenic motor output but also modifies hypoxia-induced gasping in vivo by increasing gasp frequency. Although ionotropic EAA receptor activation in this region appears to be required for the generation of eupneic breathing, it remains to be determined whether similar activation is necessary for the production and/or expression of hypoxia-induced gasping. Therefore, we examined the effects of severe brain hypoxia before and after blockade of ionotropic EAA receptors in the pre-BötC in eight chloralose-anesthetized, deafferented, mechanically ventilated cats. In each experiment, before blockade of ionotropic EAA receptors in the pre-BötC, severe brain hypoxia (6% O2 in a balance of N2 for 3-6 min) produced gasping. Although bilateral microinjection of the broad-spectrum ionotropic EAA receptor antagonist kynurenic acid (20-100 mM; 40 nl) into the pre-BötC eliminated basal phrenic nerve discharge, severe brain hypoxia still produced gasping. Under these conditions, however, the onset latency to gasping was increased ( P < 0.05), the number of gasps was reduced for the same duration of hypoxic gas exposure ( P < 0.05), the duration of gasps was prolonged ( P < 0.05), and the duration between gasps was increased ( P < 0.05). These findings demonstrate that hypoxia-induced gasping in vivo does not require activation of ionotropic EAA receptors in the pre-BötC, but ionotropic EAA receptor activation in this region may modify the expression of the hypoxia-induced response. The present findings also provide additional support for the pre-BötC as the primary locus of respiratory rhythm generation.
Influence of exercise on dilatation of the basilar artery during diabetes mellitus
Authors: Mayhan William G. , Sun Hong , Mayhan Jill F. , Patel Kaushik P.
Published: April 2004

Our goal was to examine whether exercise training alleviates impaired nitric oxide synthase (NOS)-dependent dilatation of the basilar artery in Type 1 diabetic rats. To test this hypothesis, we measured in vivo diameter of the basilar artery in sedentary and exercised nondiabetic and diabetic rats in response to NOS-dependent (acetylcholine) and -independent (nitroglycerin) agonists. To determine the potential role for nitric oxide in vasodilatation in sedentary and exercised nondiabetic and diabetic rats, we examined responses after NG-monomethyl-l-arginine (l-NMMA). We found that acetylcholine produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic rats. Acetylcholine produced only minimal vasodilatation in sedentary diabetic rats. However, exercise alleviated impaired acetylcholine-induced vasodilatation in diabetic rats. Nitroglycerin produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic and diabetic rats. l-NMMA produced similar inhibition of acetylcholine-induced dilatation of the basilar artery in sedentary and exercised nondiabetic and diabetic rats. Finally, we found that endothelial NOS (eNOS) protein in the basilar artery was higher in diabetic compared with nondiabetic rats and that exercise increased eNOS protein in the basilar artery of nondiabetic and diabetic rats. We conclude that 1) exercise can alleviate impaired NOS-dependent dilatation of the basilar artery during diabetes mellitus, 2) the synthesis and release of nitric oxide accounts for dilatation of the basilar artery to acetylcholine in sedentary and exercised nondiabetic and diabetic rats, and 3) exercise may exert its affect on cerebrovascular reactivity during diabetes by altering levels of eNOS protein in the basilar artery.
Cardioprotective effects of exercise training on myofilament calcium activation in ovariectomized rats
Authors: Bupha-Intr Tepmanas , Wattanapermpool Jonggonnee
Published: April 2004

The risks associated with hormone replacement therapy, especially cardiac diseases in postmenopausal women, have prompted extensive studies for other preventive or therapeutic alternatives. We investigated the cardioprotective effects of exercise training on the changes in cardiac myofilament Ca2+ activation in 10-wk-old ovariectomized rats. The exercise groups were subjected to a 9-wk running program on a motor-driven treadmill 1 wk after surgery. The relationship between pCa (-log molar free Ca2+ concentration) and myofibrillar MgATPase activity of exercise-sham myofibrils or exercise-ovariectomized myofibrils was the same and could not be distinguished from that of sedentary-sham control hearts. In contrast, a significant suppression in maximum MgATPase activity and a leftward shift of pCa50 (half-maximally activating pCa) in the pCa-ATPase activity relationship were detected in sedentary-ovariectomized rats. Exercise training also prevented the shift in myosin heavy chain (MHC) isoforms toward β-MHC in ovariectomized hearts. The upregulation of β1-adrenergic receptors in the left ventricular membranes of ovariectomized rat hearts, as measured by receptor binding and immunoblot analyses, was no longer observed in exercise-ovariectomized hearts. Immunoblot analyses of heat shock protein (HSP) 72, an inducible form of HSP70, demonstrated a significant downregulation in ovariectomized hearts. Exercise training in ovariectomized rats completely reversed the expression of HSP72 to the same level as sham controls. Our results clearly indicate the cardioprotective effects of exercise training on changes in cardiac myofilament Ca2+ activation in ovariectomized rats. Alterations in expression of β1-adrenergic receptors and HSP72 may, in part, play a mechanistic role in the cardioprotective effects.
II. Caspian Energy: Oil and Gas Resources and the Global Market
Authors: Amineh Mehdi Parvizi , Houweling Henk
Published: April 2004

This article develops several concepts of critical geopolitics and relates them to the energy resources of the Caspian Region. Energy resources beyond borders may be accessed by trade, respectively by conquest, domination and changing property rights. These are the survival strategies of human groups in the international system. The article differentiates between demand-induced scarcity, supply-induced scarcity, structural scarcity and the creation, respectively, transfer of property rights. Together, the behaviors referred to by these concepts create a field of social forces that cross state borders involving state and a variety of non-state actors. During World War II, the US began to separate the military borders of the country from its legal-territorial borders. By dominating the world's oceans, the Anglo-Saxon power presided over the capacity to induce scarcity by interdicting maritime supplies to allies and enemies alike. Today, overland transport increasingly connects economies and energy supplies on the Eurasian continent. The US has therefore to go on land in order to pre-empt the land-based powers from unifying their economies and energy supplies.
III. Nation-State Building in Central Asia: A lost Case?
Authors: Akçali Pinar
Published: April 2004

With the collapse of the Soviet Union in 1991, the five Central Asian republics of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan have entered a period of nationstate building, which had been started to a large extend by the political elites of the former Soviet Union. These republics were not prepared for independence that came to the region suddenly. The former communist leaders of the Soviet era became the new national elites to take their countries by publicly declared goals and policies through the path of independent nationhood and independent statehood. However, it remains unclear whether this top-to-bottom approach will prove successful in the long run. This article discusses nationstate building in the region by first looking at problems of external sovereignty. Second, domestic state building policies and structures, more specifically, the newly formulated official discourse on-building nation- and the political-legal framework to develop that discourse, are analyzed. Then, the limitations of this process with specific emphasis on supranational identities (basically religious identity of Islam), subnational identities (local and/or tribal identities), and ethnic minorities (with a specific on the Russians in these five countries) are examined. It is concluded that the process of nation-state building in Central Asia is not complete yet and that each republic has unique problems that may challenge this process. For the time being, there exist certain frictions between the goals of the official discourse and nonofficial levels of identity that may hinder the success of the nation building process in the region.
IV. Political Processes in Post-Soviet Central Asia
Authors: Akiner Shirin
Published: April 2004

The Central Asian republics inherited a high degree of civic order. The challenge that confronts these republics today is whether or not, as independent states, they will be able to maintain order and stability; and if so, by what means will they achieve this. It is unlikely that in the near future these newly independent states will be able to mobilize sufficient resources to sustain the level of development achieved under Soviet rule. Standards in health care and education are showing signs of severe erosion; the general social and technical infrastructure, especially in rural areas, is deteriorating owing to inadequate maintenance and investment. If this regression continues, it is likely to have potentially disastrous political consequences. Pauperization, frustrated hopes, bitter competition for scarce resources, as well as the increasing gap between aspirations and the ability to satisfy them, could provide a fertile breeding ground for intercommunal violence, as has already occurred in Tajikistan. In some areas, particularly in the south, this is finding expression in a militant form of Islam. When the Soviet Union collapsed in 1991, there were many who cherished the same hopes for the Central Asian republics that had previously been held for the newly decolonized world of the 1950s, namely, that it would be possible to launch these states on a smooth process of cultural change, economic growth, and stable democracy. The reality here, as in other parts of the developing world, has already proved to be far more complex. To consolidate genuine political and economic reform will require a fundamental shift in social and cultural attitudes.
V. The Economic and Social Impact of Systemic Transition in Central Asia and Azerbaijan
Authors: Kaser Michael
Published: April 2004

The economies of Azerbaijan, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan differ from the other states that quit the Soviet Union in 1991 by their inheritance of poor productivity growth and high demographic pressure for job creation. Moreover, since their incorporation into the Russian Empire during the nineteenth century, their production has been geared to primary goods - cotton and hydrocarbons - that in the 1930s Stalin's policy towards autarky was directed to Soviet domestic consumption. The six countries hence gained independence, but with high export dependency on markets that all suffered severe demand recessions. The corresponding production decline in the six states was modified during the 1990s by diversifying the direction of trade and was not as deep as indicated by the official GDP data by reason of the substantial growth of unmeasured production. That 'shadow economy' goes untaxed and all six states show government revenue inadequate for the social expenditure required to maintain the stock of human capital inherited from Soviet planning priorities and to reverse the widening of income differentials, as well as for capital formation to employ the expanding labor force. Some improvement has resulted from emigration and foreign investment by Kazakhstan, and from foreign investment by Azerbaijan. But that inflow has enhanced those states' dependence on hydrocarbons and the danger of a "Dutch disease." In all six states, authoritarian and corruption-prone governance inhibit foreign investment, though in two, Azerbaijan and Kazakhstan, state funds have been established so that eventual income from fixed assets replace that from depleting hydrocarbon deposits.
VI. Gendered Transitions: The Impact of the Post-Soviet Transition on Women in Central Asia and the Caucasus
Authors: Ishkanian Armine
Published: April 2004

In this chapter, I explore the impact of the post-Soviet political and socioeconomic transitions on women in the former Soviet republics of Central Asia and the Caucasus. I review the impact of Soviet policies on gender roles and relations in order to contextualize post-Soviet developments. The central segment, which examines gender roles and relations after socialism, is divided into two sections. In the first section, I examine the impact of local political and socioeconomic transitions on gender relations and local responses to those transitions. In the second section, I discuss the impact of regional/global events and interactions on gender roles and relations. Throughout the chapter, I consider the similarities and differences of the transitions and the responses to those transitions in the post-Soviet republics of Central Asia and the Caucasus.
VII. Sino-Indian Relations: Security Dilemma, Ideological Polarization, or Cooperation Based on 'Comprehensive Security'?
Authors: Radtke Kurt
Published: April 2004

Geopolitics in Central Asia are not wholly determined by its giant neighbors China, India, and Russia, but the strategic approaches adopted by these three countries have a major impact on the dynamics of Central Asia. This contribution aims to throw more light on the nature of the strategic and security discourse between China and India as one way to increase our understanding of the context in which Central Asian states operate. Despite globalization, Asian governments tend to cling to static approaches. China in particular emphasizes the role of "large powers" (daguo) in determining the global structure, and regards itself as one of those large powers. Cooperation with other powers demands a minimum level of agreement on common goals for the future global system, but recent emphasis on moral, and thus ideological elements in US global strategies has the potential to reimpose ideological polarization on the global system. Countries in Southeast or Central Asia tend to adopt policies of diversification by strengthening their links with all major global powers, including the United States, hoping to avoid polarization while at the same time staying clear of bandwagoning. This is one of the reasons why the New Great Game cannot simply be described in terms of Great Powers that engage among themselves in maneuvers of bandwagoning and balancing. Sharing concepts such as "comprehensive security" may provide greater leeway for policymakers who do not wish to become prisoners of man-made dilemmas. Nineteenth-century concepts of balance of power seem no shining beacon for policymakers of Eurasia and the United States in the twenty-first century.
VIII. The US and the EU in CEA Relations with Regional Powers
Authors: Amineh Mehdi Parvizi , Houweling Henk
Published: April 2004

The US and the EU are important external actors in the post-Soviet CEA region. One challenge confronting US policymakers is balancing commercial interests in the region with security interests and foreign policy goals. These include a desire to contain Iran, partly because of its support for radical Islamic forces in the Middle East, to prevent regional conflicts, assist NATO-member Turkey—a critical ally in an area that is of top US-security interest, and to normalize its relations with China, whose military potential and alliance with Russia is perceived as a threat to its own security interests. Commercially, the EU is not as involved in CEA as the US. The main powers in the EU—Britain, France and Germany— give priority to other regions over CEA. Britain puts emphasis on the Baltic States, France focuses on North Africa, and Germany has been more preoccupied with the development of Eastern Europe. As a group, the member countries of the EU act mostly in the context of economic assistance and diplomatic contacts. Military agreements have been signed on a bilateral basis mostly with Georgia.
XII. A Transnational Policy for Conflict Reduction and Prevention in the South Caucasus
Authors: Cutler Robert
Published: April 2004

This article examines conflicts in the South Caucasus with a view towards means for their interdependent resolution. It begins by reviewing briefly in succession situations in Georgia: Abkhazia, Ajaria, Javakhetia, and Tskhinvali (South Ossetia). A comparative qualitative analysis then follows that is heuristic rather than definitive. The situation in Mountainous Karabagh is juxtaposed to this, and complicating factors are identified. On that basis, a policy initiative for the South Caucasus is described, building upon the extensive considerations previously elaborated on in a report by the Centre for European Policy Studies. A focus on nongovernmental actors in particular leads to reflections on how to create potential transgovernmental and transsocietal sociopolitical coalitions for conflict reduction and prevention. Specifically, possibilities are considered for moving toward an institution such as a transnational Assembly for Regions and Peoples of the South Caucasus. Issues of institutional design are considered and assessed on the basis of existing comparative work on international parliamentary formations.
Modelling and experimental study on bending vibration of a diesel engine crankshaft
Authors: Lü Xing-Cai , Huang Zhen , Shu Ge-Qun
Published: April 2004

In recent years, a considerable amount of research effort has gone into the investigation of free and/or forced vibration characteristics of a spinning shaft with attached discs, but there has been less research on the transverse vibration of a high-speed diesel engine crankshaft system under firing conditions. This paper presents a new exact general approach based on a distributed continuous model to study the free and forced bending vibrations of an engine crankshaft. Distributed continuous models of the crankshafts for a four-cylinder (with a capacity of 3.8 l) and an in-line six-cylinder (with a capacity of 5.8 l) direct-injection diesel engine were constructed. The general frequency equation and mode shapes for the bending vibration of the total crankshaft under operating conditions were obtained using the coefficients transfer matrix method. Modelling and analysis procedures were applied to the crankshaft systems of two diesel engines, and the inherent frequencies of the crankshaft within overall engine speeds were calculated. Then, equations to simulate the steady state vibration amplitudes when the gas forces, rotating masses and reciprocating masses exerted at the crankshaft were deduced. The bending amplitudes at the front free end of the crankshaft were calculated using this method. To verify the modelling and the results of the calculations, the bending vibrations were measured at the front end of the crankshaft using a newly designed device. It is found that there was good agreement between the analytical results and the experimental results.
A thermomechanical model of a direct injection diesel engine piston
Authors: Abbes M Tahar , Maspeyrot P , Bouif A , Frene J
Published: April 2004

This article presents a three-dimensional finite element full analysis, which describes the thermomechanical behaviour of a direct injection diesel engine piston. The piston moving in a complex environment is exposed to several interactions during engine operation. The thermomechanical model takes in account the most important load. The piston is subjected to the coupled action of the thermal loads due to the transfer of heat from the head to the body and the mechanical load represented by the combustion pressure and the inertial load due to the important change of direction of the piston in the cylinder bore.

The response of the simulated model by critical loads makes it possible to know and to analyse the operating temperatures, the corresponding thermal expansion and the thermomechanical deformations and stresses. The results obtained will be the source data for the development of a global elastohydrodynamic model and will provide a good tool for piston design.