Min Of Occlusion Research Articles

Evidence from functional ultrasound imaging of enhanced contralesional microvascular response to somatosensory stimulation in acute middle cerebral artery occlusion/reperfusion in rats: A marker of ultra-early network reorganization?

Following middle cerebral artery (MCA) stroke, enhanced contralesional evoked responses have been consistently reported both in man and rodents as part of plastic processes thought to influence motor recovery. How early this marker of large-scale network reorganization develops has however been little addressed, yet has clinical relevance for rehabilitation strategies targeting plasticity. Previous work in mice has reported enhanced contralesional responses to unaffected-side forepaw stimulation as early as 45 min after MCA small branch occlusion. Using functional ultrasound imaging (fUSi) in anesthetized rats subjected to distal temporary MCA occlusion (MCAo), we assessed here (i) whether enhanced contralesional responses also occurred with unaffected-side whisker pad stimulation, and if so, how early after MCAo; and (ii) the time course of this abnormal response during occlusion and after reperfusion. We replicate in a more proximal MCA occlusion model the earlier findings of ultra-early enhanced contralesional evoked responses. In addition, we document this phenomenon within minutes after MCAo, and its persistence throughout the entire 90-min occlusion as well as 90-min reperfusion periods studied. These findings suggest that plastic processes may start within minutes following MCAo in rodents. If replicated in man, they might have implications regarding how early plasticity-enhancing therapies can be initiated after stroke.

The role of nitric oxide in the protective action of remote ischemic per-conditioning against ischemia/reperfusion-induced acute renal failure in rat.

Objective(s):We investigated the role of nitric oxide (NO) in the protective effects of remote ischemic per-conditioning (rIPerC) on renal ischemia/reperfusion (I/R) injury in male rats.Materials and Methods:I/R treatment consisted of 45 min bilateral renal artery ischemia and 24 hr reperfusion interval. rIPerC was performed using four cycles of 2 min occlusions of the left femoral artery and 3 min reperfusion at the beginning of renal ischemia. The animals were given normal saline (vehicle), NG-nitro-L-arginine methyl ester (L-NAME) or L-arginine. Following the reperfusion period, renal functional- and oxidative stress- parameters, as well as histopathological changes were assessed.Results:In comparison with the sham group, I/R resulted in renal dysfunction, as indicated by significantly lower creatinine clearance and higher fractional excretion of sodium. This went along with decreased glutathione peroxidase (GPX) and catalase (CAT) activity in the I/R group, increased malondialdehyde (MDA) contents and histological damages. In comparison with the I/R group, the rIPerC group displayed improved renal function, increased activity of GPX and CAT enzymes, and decreased MDA level. However, these effects were abrogated by L-NAME injection and augmented by L-arginine treatment.Conclusion:According to the results, the functional and structural consequences of rIPerC against I/R-induced kidney dysfunction, which is associated with reduction of lipid peroxidation and intensification of anti-oxidant systems, is partially dependent on NO production.

Knockdown of TNF‑α alleviates acute lung injury in rats with intestinal ischemia and reperfusion injury by upregulating IL‑10 expression.

Intestinal ischemia and reperfusion (II/R) injury often triggers severe injury in remote organs, with the lungs being considered the main target. Excessive elevation of proinflammatory cytokines is a major contributor in the occurrence and development of II/R-induced acute lung injury (ALI). Therefore, the present study aimed to investigate whether blocking tumor necrosis factor-α (TNF-α) expression could protect the lungs from injury following II/R, and to explore the possible underlying mechanism involving interleukin-10 (IL-10). Briefly, II/R was induced in rats by 40 min occlusion of the superior mesenteric artery and celiac artery, followed by 8, 16 or 24 h of reperfusion. Subsequently, lentiviral vectors containing TNF-α short hairpin (sh)RNA were injected into the right lung tissues, in order to induce TNF-α knockdown. The severity of ALI was determined according to lung injury scores and lung edema (lung wet/dry weight ratio). The expression levels of TNF-α were analyzed by quantitative polymerase chain reaction (qPCR), western blotting and immunofluorescence (IF) staining. IL-10 expression, in response to TNF-α knockdown, was detected in lung tissues by qPCR and IF. The results detected marked inflammatory responses, and increased levels of lung wet/dry weight ratio and TNF-α expression, in the lungs of II/R rats. Conversely, treatment with TNF-α shRNA significantly alleviated the severity of ALI and upregulated the expression levels of IL-10 in lung tissues. These findings suggested that TNF-α RNA interference may exert a protective effect on II/R-induced ALI via the upregulation of IL-10. Therefore, TNF-α knockdown may be considered a potential strategy for the prevention or treatment of ALI induced by II/R in future clinical trials.

Modification of gene expression profiling related to renin-angiotensin system in an ischemia/reperfusion rat model after T3 infusion.

Triiodothyronine (T3) and renin-angiotensin system (RAS) are functionally related in cardiovascular system. Recently, in an in vivo myocardial ischemia/reperfusion (I/R) model in rats, we showed that T3 treatment improved the post-ischemic recovery of cardiac function. In the present study, we used the same experimental model of regional I/R, obtained by 30min occlusion of the left descending coronary artery, followed by 3-days of reperfusion, to investigate the effect of 48-h treatment (started 1day after ischemia) with 6µg/kg/day T3 or vehicle. T3 was delivered by constant subcutaneous infusion via miniosmotic pump. In particular, aim of this work is to evaluate the effects of T3 on the gene expression of the main receptors and enzymes involved in the two cardiac arms of RAS in an in vivo rat model of I/R: AT1R-ACE (detrimental arm) and AT2R/MAS1-ACE2 (protective arm). Gene expression was evaluated by Real-Time PCR in infarct zone (Area-At-Risk: AAR) and in tissues distant from ischemic wound (Remote Zone: RZ). Three different rat groups were used: sham-operated; I/R and I/R + T3. Main result of the study is the opposite response of AT1R and AT2R/MAS1 expression to I/R procedure and to T3 administration after I/R in both AAR and RZ. Moreover, T3 significantly increased ACE and ACE2 enzyme expression in AAR and RZ. This study reveals that T3 stimulates the expression of protective genes related to RAS such as AT2R/MAS1-ACE2 mainly in BZ, suggesting that, at least in part, T3 could be involved in the local cardiac ameliorative response to I/R procedure.

Acute Resistance Exercise Effects on Blood Flow in Resistance-Trained Versus Untrained Individuals

Data suggests that an acute bout of resistance exercise (ARE) increases forearm blood flow (FBF) and vasodilatory capacity compared to rest. However, the effects of training status on FBF and vasodilatory capacity at rest and during recovery from ARE are uncertain. PURPOSE: To compare the effects of resistance exercise training status on measures of vascular function at rest and recovery from ARE. METHODS: Fifteen resistance-trained (RT) individuals, and seven untrained (UT) individuals volunteered to participate. Measurements were taken after a 10min supine rest and 20min after ARE, or a control. Venous occlusion plethysmography was used to measure FBF and vasodilatory capacity, with 5min of occlusion (220mmHg) to induce reactive hyperemia. Area under the curve (AUC) was utilized to determine differences in blood flow. The ARE consisted of 3 sets of 10 repetitions at 75% 1-repetition maximum (1RM) on the leg press, leg curl, leg extension, lat pulldown, and chest press, with 2min of rest between sets and exercises. A 2x2x2 repeated measures ANOVA was used to evaluate group (RT, UT) across condition (ARE, control) and time (rest, recovery). If the ANOVA was significant, t-tests were used for post-hoc comparisons. RESULTS: Groups were similar (p>0.05) for age, height, and BMI, but not for weight (RT: 74.5±13.0kg; UT: 61.9±10.8kg, p=0.04). The 1RMs for chest press, leg curl, leg press, and lat pulldown were significantly different between groups (p<0.05), but not for leg extension (p=0.26). The total volume of exercise for the ARE was similar between groups (p=0.10). There were no significant (p>0.05) group differences at rest for FBF or vasodilatory capacity. There were no significant (p>0.05) 3-way interactions for FBF or vasodilatory capacity. There was a significant condition by time interaction for FBF (RT: rest: 2.9±1.1ml/100ml of tissue/min, recovery: 8.9±4.0ml/100ml of tissue/min; UT: rest: 3.1±1.1ml/100ml of tissue/min, recovery: 8.9±2.9ml/100ml of tissue/min; p<0.001) and AUC (RT: rest: 56.8±20.2units, recovery: 139.0±66.5units; UT: rest: 53.8±20.2units, recovery: 116.6±25.1units; p<0.001). CONCLUSION: These data demonstrate that acute resistance exercise significantly increases forearm blood flow and vasodilatory capacity regardless of training status.

Efficacy of Novel Carbon Nanoparticle Antioxidant Therapy in a Severe Model of Reversible Middle Cerebral Artery Stroke in Acutely Hyperglycemic Rats.

While oxidative stress can be measured during transient cerebral ischemia, antioxidant therapies for ischemic stroke have been clinically unsuccessful. Many antioxidants are limited in their range and/or capacity for quenching radicals and can generate toxic intermediates overwhelming depleted endogenous protection. We developed a new antioxidant class, 40 nm × 2 nm carbon nanoparticles, hydrophilic carbon clusters, conjugated to poly(ethylene glycol) termed PEG-HCCs. These particles are high-capacity superoxide dismutase mimics, are effective against hydroxyl radical, and restore the balance between nitric oxide and superoxide in the vasculature. Here, we report the effects of PEG-HCCs administered during reperfusion after transient middle cerebral artery occlusion (tMCAO) by suture in the rat under hyperglycemic conditions. Hyperglycemia occurs in one-third of stroke patients and worsens clinical outcome. In animal models, this worsening occurs largely by accelerating elaboration of reactive oxygen species (ROS) during reperfusion. PEG-HCCs were studied for their protective ability against hydrogen peroxide in b.End3 brain endothelial cell line and E17 primary cortical neuron cultures. In vivo, hyperglycemia was induced by streptozotocin injection 2 days before tMCAO. 58 Male Sprague-Dawley rats were analyzed. They were injected IV with PBS or PEG-HCCs (4 mg/kg 2×) at the time of recanalization after either 90- or 120-min occlusion. Rats were survived for up to 3 days, and infarct volume characteristics and neurological functional outcome (modified Bederson Score) were assessed. PEG-HCCs were protective against hydrogen peroxide in both culture models. In vivo improvement was found after PEG-HCCs with 90-min ischemia with reduction in infarct size (42%), hemisphere swelling (46%), hemorrhage score (53%), and improvement in Bederson score (70%) (p = 0.068-0.001). Early high mortality in the 2-h in the PBS control group precluded detailed analysis, but a trend was found in improvement in all factors, e.g., reduction in infarct volume (48%; p = 0.034) and a 56% improvement in Bederson score (p = 0.055) with PEG-HCCs. This nano-antioxidant showed some improvement in several outcome measures in a severe model of tMCAO when administered at a clinically relevant time point. Long-term studies and additional models are required to assess potential for clinical use, especially for patients hyperglycemic at the time of their stroke, as these patients have the worst outcomes.

Gualou Xiebai Decoction, a Traditional Chinese Medicine, Prevents Cardiac Reperfusion Injury of Hyperlipidemia Rat via Energy Modulation.

Background: Gualou Xiebai Decoction (GLXB) is a classic prescription of Chinese medicine used for the treatment of cardiac problems. The present study was designed to explore the effect and mechanism of GLXB on ischemia/reperfusion (I/R) induced disorders in myocardial structure and function, focusing on the regulation of energy metabolism and the RhoA/ROCK pathway.Methods: After hyperlipidemic rat model was established by oral administration of high fat diet, the rats were treated with GLXB for 6 weeks and subjected to 30 min occlusion of the left anterior descending coronary artery (LADCA) followed by 90 min reperfusion to elicit I/R challenge. Myocardial infarct size was assessed by Evans blue-TTC staining. Myocardial blood flow (MBF) and cardiac function were evaluated. Enzyme-linked immunosorbent assay was performed to examine the content of ATP, ADP, AMP, CK, CK-MB, LDH, cTnT, cTnI, and IL-6. Double staining of F-actin and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling was conducted to assess myocardial apoptosis. Expressions of ATP synthase subunit δ (ATP 5D), and RhoA and ROCK were determined by Western blotting.Results: Administration with GLXB at high dose for 6 weeks protected heart against I/R-induced MBF decrease, myocardial infarction and apoptosis, ameliorated I/R-caused impairment of cardiac function and myocardial structure, restored the decrease in the ratio of ADP/ATP and AMP/ATP, and the expression of ATP 5D with inhibiting the expression of RhoA and ROCK.Conclusions: Treatment with GLXB effectively protects myocardial structure and function from I/R challenge, possibly via regulating energy metabolism involving inactivation of RhoA/ROCK signaling pathway.

Summation and Cancellation Effects on QRS and ST-Segment Changes Induced by Simultaneous Regional Myocardial Ischemia

Simultaneous ischemia in two myocardial regions is a potentially lethal clinical condition often unrecognized whose corresponding electrocardiographic (ECG) patterns have not yet been characterized. Thus, this study aimed to determine the QRS complex and ST-segment changes induced by concurrent ischemia in different myocardial regions elicited by combined double occlusion of the three main coronary arteries. For this purpose, 12 swine were randomized to combination of 5-min single and double coronary artery occlusion: Group 1: left Circumflex (LCX) and right (RCA) coronary arteries (n = 4); Group 2: left anterior descending artery (LAD) and LCX (n = 4) and; Group 3: LAD and RCA (n = 4). QRS duration and ST-segment displacement were measured in 15-lead ECG. As compared with single occlusion, double LCX+RCA blockade induced significant QRS widening of about 40 ms in nearly all ECG leads and magnification of the ST-segment depression in leads V1–V3 (maximal 228% in lead V3, p < 0.05). In contrast, LAD+LCX or LAD+RCA did not induce significant QRS widening and markedly attenuated the ST-segment elevation in precordial leads (maximal attenuation of 60% in lead V3 in LAD+LCX and 86% in lead V5 in LAD+RCA, p < 0.05). ST-segment elevation in leads V7–V9 was a specific sign of single LCX occlusion. In conclusion, concurrent infero-lateral ischemia was associated with a marked summation effect of the ECG changes previously elicited by each single ischemic region. By contrast, a cancellation effect on ST-segment changes with no QRS widening was observed when the left anterior descending artery was involved.

Blood Pressure Predicts Endothelial Function and Effect of Ethinyl Estradiol in Young Obese and Lean Women

Obesity, mild hypertension and endothelial function are all predictors of cardiovascular disease in women, and we propose that these factors are interrelated. We hypothesized that obesity and high blood pressure are associated with endothelial dysfunction in young women. Further, we hypothesized that short‐term low‐dose ethinyl estradiol treatment would mitigate this dysfunction. We examined hyperemic responses before and during 30 μg/day oral ethinyl estradiol (EE) treatment for 7 days in 16 healthy women (mean 26 ± 5, 19–35 yrs) with normal (NBP; n=7, MAP range: 78–91 mmHg) or mildly elevated blood pressure (HBP; n=9, MAP range: 95–113 mmHg). We evaluated brachial vasodilatory responses following two stimuli designed to elicit different levels of shear stress: 5‐min occlusion (RH‐FMD), and 3‐min occlusion with ischemic handgrip exercise (IE‐FMD). Body composition did not impact RH‐FMD or IE‐FMD responses. In contrast, Pre‐EE, HBP had lower IE‐FMD responses relative to NBP (8.0 ± 3.5% vs. 12.3 ± 3.2%, respectively; P=0.05). During EE, IE‐FMD increased in HBP (12.8 ± 6.1%; P=0.02) and decreased in NBP (5.6 ± 2.4%, P&lt;0.01). The increase in shear stress (8659 ± 4964 vs. 14753 ± 8189 AUC, s−1; P=0.04) contributed to the increase in IE‐FMD in HBP subjects during EE, while shear stress did not change with EE in NBP (9740 ± 3222 vs. 10564 ± 2984 AUC, s−1; P=0.76). MAP did not predict RH‐FMD responses or associated shear stress, pre‐or during‐EE. Thus, 1) in young healthy women, moderately elevated blood pressure was a predictor of endothelial function whereas obesity was not; 2) EE mitigated endothelial dysfunction associated with elevated blood pressure; 3) the enhanced shear stress stimulus was able to subtle differences in endothelial function where the standard FMD stimulus did not. Because HBP women had only mildly high blood pressure, these data are of particular significance given the new American Heart Association guidelines for hypertension.Support or Funding InformationSupported by the APS Undergraduate Research Excellence Fellowship; the Paul Titus Fellowship Fund, Dept. Obstetrics Gynecology and Reproductive Sciences, Yale School of Medicine; and the AHA Postdoctoral Fellowship.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Ginsenoside Rg1 Ameliorates Rat Myocardial Ischemia‐Reperfusion Injury by Modulating Energy Metabolism Pathways

BackgroundThe present study was designed to investigate the protective effect and mechanisms of ginsenoside Rg1 (Rg1) against heart ischemia‐reperfusion (I/R) injury, with focusing on energy metabolism.Methods and resultsMale Sprague‐Dawley rats were subjected to 30 min occlusion of left coronary anterior descending artery followed by reperfusion for 90 min. Rg1 (5 mg/kg/hour) was continuous administrated intravenously 30 min before occlusion until the end of reperfusion. Myocardial infarct size, blood flow, myocardial function, structure and apoptosis, energy metabolism and change in Ras homolog gene family, member A (RhoA) signaling pathway during cardiac I/R injury were evaluated. Binding of Rg1 to RhoA was assessed using Surface Plasmon Resonance. Rg1 prevented I/R‐elicited insults in myocardium, including myocardial apoptosis, decreased myocardial blood flow and cardiac dysfunction, alteration in myocardium structure, and apoptosis. In addition, Rg1 restored the production of ATP during cardiac I/R. Furthermore, Rg1 was able to bind to RhoA and down‐regulate the activity of RhoA signaling pathway.ConclusionThese results indicated that Rg1 had protective potential against I/R‐induced myocardial injury, which may be related to inhibiting myocardial apoptosis and modulating energy metabolism through binding to RhoA inactivating RhoA signaling pathway.Support or Funding InformationThis work was supported by the National Natural Science Foundation of China [81273637] for Jing‐Yan Han.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of diabetes mellitus on adenosine postconditioning-induced reduction of myocardial ischemia-reperfusion injury in rats

Objective To investigate the effect of diabetes mellitus (DM) on adenosine postconditioning-induced reduction of myocardial ischemia-reperfusion (I/R) injury in rats. Methods Adult male Sprague-Dawley rats, weighing 230-260 g, were used in the study.Type 2 DM was induced by high-fat diet and intraperitoneal l% streptozocin 35 mg/kg and confirmed by fasting blood glucose concentration>16.7 mmol/L 72 h later.Eighteen rats with type 2 DM were divided into 3 groups (n=6 each) using a random number table: sham operation group (DS group), I/R group (DI/R group) and adenosine postconditioning group (DAP group). Eighteen healthy nondiabetic rats were selected and randomly divided into 3 groups (n=6 each): sham operation group (NS group), I/R group (NI/R group) and adenosine postconditioning group (NAP group). Myocardial I/R was induced by 30 min occlusion of the left anterior descending branch of coronary artery followed by 2 h of reperfusion.Venous blood samples were collected from the femoral vein at 2 h of reperfusion for measurement of plasma cardiac troponin I (cTnI) and creatine kinase-MB (CK-MB) concentrations (by enzyme-linked immunosorbent assay). The rats were then sacrificed immediately after blood sampling for determination of the myocardial ischemic area and infarct size. Results The plasma cTnI and CK-MB concentrations were significantly increased, and the percentage of myocardial infarct size was increased after myocardial I/R in nondiabetic and diabetic rats.Adenosine postconditioning significantly decreased plasma cTnI and CK-MB concentrations and percentage of myocardial infarct size in nondiabetic and diabetic rats (P<0.05). Compared with group NAP, the plasma concentrations of cTnI and CK-MB were significantly increased, and the percentage of myocardial infarct size was increased in group DAP (P<0.05). Conclusion DM can weaken cardioprotection induced by adenosine postconditioning in rats. Key words: Diabetes mellitus; Adenosine; Ischemic postconditioning; Myocardial reperfusion injury

High-intensity interval training in hypoxia does not affect muscle HIF responses to acute hypoxia in humans.

The myocellular response to hypoxia is primarily regulated by hypoxia-inducible factors (HIFs). HIFs thus conceivably are implicated in muscular adaptation to altitude training. Therefore, we investigated the effect of hypoxic versus normoxic training during a period of prolonged hypoxia ('living high') on muscle HIF activation during acute ischaemia. Ten young male volunteers lived in normobaric hypoxia for 5 weeks (5 days per week, ~ 15.5h per day, FiO2: 16.4-14.0%). One leg was trained in hypoxia (TRHYP, 12.3% FiO2) whilst the other leg was trained in normoxia (TRNOR, 20.9% FiO2). Training sessions (3 per week) consisted of intermittent unilateral knee extensions at 20-25% of the 1-repetition maximum. Before and after the intervention, a 10-min arterial occlusion and reperfusion of the leg was performed. Muscle oxygenation status was continuously measured by near-infrared spectroscopy. Biopsies were taken from m. vastus lateralis before and at the end of the occlusion. Irrespective of training, occlusion elevated the fraction of HIF-1α expressing myonuclei from ~ 54 to ~ 64% (P < 0.05). However, neither muscle HIF-1α or HIF-2α protein abundance, nor the expression of HIF-1α or downstream targets selected increased in any experimental condition. Training in both TRNOR and TRHYP raised muscular oxygen extraction rate upon occlusion by ~ 30%, whilst muscle hyperperfusion immediately following the occlusion increased by ~ 25% in either group (P < 0.05). Ten minutes of arterial occlusion increased HIF-1α-expressing myonuclei. However, neither normoxic nor hypoxic training during 'living high' altered muscle HIF translocation, stabilisation, or transcription in response to acute hypoxia induced by arterial occlusion.

Near-infrared spectroscopy assessment of microvasculature detects difference in lower limb vascular responsiveness in obese compared to lean individuals

BackgroundMicrovascular dysfunction is an early complication in obesity-related cardiovascular disease (CVD) that can lead to changes in hemodynamic function and endothelial cell expression throughout the vasculature that is vessel specific. This study aimed to evaluate whether the near-infrared spectroscopy (NIRS) combined with a vascular occlusion (VOT) assessment was capable of detecting differences in vascular responsiveness within the microvasculature of the lower limb between lean and obese individuals. Methods and resultsTwenty lean (BMI = 21.6 ± 1.3) and 17 obese individuals (BMI = 33.9 ± 1.1) participated in the study. Individuals underwent a VOT (5 min of baseline, 5 min of occlusion, and 8 min following cuff release) and vascular responsiveness was evaluated by the Slope 2 (Slope 2 StO2) and the area under the curve (StO2AUC) of oxygen saturation (StO2) signal during reperfusion. The difference between the minimal and the maximal value of StO2 was calculated as the Amplitude of the StO2 response. The Slope 2 StO2 of the obese individuals was smaller (0.68 ± 0.07%·s−1) than the Slope 2 StO2 of the lean individuals (1.08 ± 0.13%·s−1;P < 0.05). The StO2AUC of the obese was smaller (978 ± 169%·s−1) than the StO2AUC of the lean individuals (1708 ± 168%·s−1; P < 0.001). The amplitude of StO2 was smaller in obese individuals than the lean ones (30.4 ± 2.9 vs 21.6 ± 1.3 StO2 (%), respectively; P < 0.05). There was a significant correlation between Slope 2 StO2 and StO2AUC for lean individuals (r = 0.745; P < 0.001). ConclusionThis study demonstrated differences in vascular responses within the microvasculature of the lower limb between lean and obese individuals.

Remote ischemic postconditioning protects the brain from focal ischemia/reperfusion injury by inhibiting autophagy through the mTOR/p70S6K pathway

Objective: Remote ischemic postconditioning (RIPostC) has been recognized as an applicable strategy for protecting against cerebral ischemia/reperfusion (I/R) injury. This study was performed to examine the effect of RIPostC on cerebral I/R and to explore its underlying mechanism.Methods: Healthy male SD rats (N = 36) were assigned randomly into 3 groups of 12 each: sham group, I/R model group and RIPostC group. Animal models were performed by filament insertion for 2 h with middle cerebral artery occlusion(MCAO) followed by 24 h of reperfusion. RIPostC was induced by 15 min occlusion of femoral arteries followed by 15 min of reperfusion for 3 cycles at the beginning of middle cerebral artery reperfusion. The neurological deficits, infarct size and brain edema were determined. Autophagy was examined by transmission electron microscopy (TEM). The protein levels of microtubule-associated protein light chain 3 (LC3-II), mammalian target of rapamycin (mTOR), serine/threonine kinase p70S6 kinase (p70S6K), and their phosphorylation (p-mTOR and p-p70S6K) in the brain tissue of the rats were determined by western blotting.Results: Our results suggested that RIPostC significantly reduced I/R-induced brain injury, as exhibited by a significantly decreased infarct size, mitigated brain edema and improved neurological deficits. RIPostC also significantly reduced the LC3-II/LC3-I ratio and protein expression of Beclin 1. Much less severe neuronal injury and fewer autophagosomes were observed by TEM in the RIPostC group.Conclusions: These results suggest that RIPostC attenuates cerebral I/R injury by inhibiting autophagy through the activation of the mTOR/p70S6K signaling pathway.

Abstract TP92: Microglial Kv1.3 Channels Are Rapidly Downregulated Following Transient Ischemic Stroke in Mice

Background: Microglia and CNS-infiltrating macrophages (CNS MPs) perform opposing deleterious pro-inflammatory and protective functions in ischemic stroke. Kv1.3 channels regulate pro-inflammatory microglial functions and are promising therapeutic targets to curb neuroinflammation. Since Kv1.3 channel expression in CNS MPs following ischemic stroke is unknown, we characterized Kv1.3 expression in CNS MPs at different times following ischemic stroke. Methods: In the 30-min transient middle cerebral artery occlusion (MCAO) mouse model, we performed flow cytometric assays of cell surface Kv1.3 expression (fluorescent labeled Kv1.3 blocking peptide ShK-F6CA) and phycoerythrin-microsphere phagocytosis on acutely isolated CNS MPs from ipsi- and contralateral hemispheres (including sham surgery controls) at 30 min, 24h, 48h, 72h and 7d time points. Among CD11b + CNS MPs, resting microglia (CD45 low Ly6c low ), activated microglia (C45 high Ly6c low ) and infiltrating macrophages (CD45 high Ly6c high ) were monitored. By quantitative PCR, we measured Kv1.3, Kir2.1 potassium channel and COX2 gene expression in CD11b + CNS MPs. Results: After 48h following MCAO, proportions of activated microglia and infiltrating macrophages were increased ipsilaterally. Kv1.3 channels were highly expressed in CD45 high Ly6c low activated microglia at baseline but significantly declined after 48 hours ipsilaterally with same trend contralaterally. Kv1.3 mRNA in CNS MPs also showed an overall decreasing trend ipsilateral to MCAO. No changes in phagocytic properties were observed following MCAO. Conclusions: Despite increased proportions of activated microglia and infiltrating macrophages, a precipitous downregulation of Kv1.3 channel expression occurs in CD45 high activated microglia after 48 hours following transient cerebral ischemia in mice. Early microglial Kv1.3 channel blockade effects on neuroinflammation following ischemic stroke need to be determined.

Mechanism underlying inhibition of inflammatory responses induced by α7nAChR agonist postconditioning alone or in combination with remote limb ischemic postconditioning during myocardial I/R in rats: the relationship with GSK-3β

Objective To evaluate the relationship between the mechanism underlying inhibition of inflammatory responses induced by α7 nicotinic acetylcholine receptor(α7nAChR)agonist postconditioning alone or in combination with remote limb ischemic postconditioning during myocardial ischemia-reperfusion(I/R)and glycogen synthase kinase-3β(GSK-3β)in rats. Methods Eighty adult male Sprague-Dawley rats, aged 8 weeks, weighing 290-320 g, were divided into 4 groups(n=20 each)using a random number table: I/R group, α7nAChR agonist postconditioning group(group P), remote limb ischemic postconditioning group(group L)and α7nAChR agonist postconditioning plus remote limb ischemic postconditioning group(group P+ L). Myocardial I/R was induced by 30 min occlusion of the left anterior descending branch of coronary artery followed by 120 min reperfusion.Specific α7nAChR agonist PNU282987 2 mg/kg was intravenously injected immediately before reperfusion in group P. In group L, limb ischemia was induced by tourniquet occlusion of bilateral hind paws for 10 min starting from 20 min of myocardial ischemia, and the tourniquet was released at the beginning of reperfusion.Combination of intervention measures previously described in P and L groups was performed in group P+ L.Venous blood samples were taken at 120 min of reperfusion for determination of serum troponin I(TnI)and creatine kinase-MB(CK-MB)concentrations, myocardial infarct size(IS)and expression of phosphorylated GSK-3β [p-GSK-3β(Ser536)], NF-κBp65 and phosphorylated nuclear factor-κBp65(p-NF-κBp65)in myocardial tissues(by Western blot). Results Compared with group I/R, myocardial IS and serum cTnI and CK-MB concentrations were significantly decreased, the expression of p-GSK-3β(Ser9)in ischemic area was up-regulated, and the expression of p-NF-κBp65 in ischemic area was down-regulated in P, L and P+ L groups(P<0.05). Compared with group L, myocardial IS and serum cTnI and CK-MB concentrations were significantly decreased, the expression of p-GSK-3β(Ser9)in ischemic area was up-regulated, and the expression of p-NF-κBp65 in ischemic area was down-regulated in group P+ L(P<0.05). Conclusion The mechanism by which α7nAChR agonist postconditioning alone or in combination with remote limb ischemic postconditioning inhibits inflammatory responses during myocardial I/R may be related to inhibiting GSK-3β activity in rats. Key words: Myocardial reperfusion injury; Inflammation; Glycogen synthase kinase 3; Cholinergic agonists; Extremities; Ischemic postconditioning

Ischemic Preconditioning: No Influence on Maximal Sprint Acceleration Performance.

Ischemic preconditioning (IPC) was initially developed to protect the myocardium from ischemia through altered cardiocyte metabolism. Because of the observed effects on metabolism and oxygen kinetics, IPC gained interest as a potential ergogenic aid in sports. Limited research evaluating the effects of IPC on maximal short-duration activities has been performed, and of the existing literature, mixed outcomes resulting from intrasubject variation may have clouded the efficacy of this technique for enhancing sprint performance. Therefore, the current study employed a randomized repeated-measures crossover design with IPC, placebo (SHAM), and control conditions while using sprint-trained athletes (N = 18) to determine the effect of IPC (3 × 5-min occlusions, with 5-min reperfusion), concluding 15min prior to maximal 10-s and 20-m sprinting. A visual analog scale was used in conjunction with the sprint trials to evaluate any possible placebo effect on performance. Despite a "significantly beneficial" perception of the IPC treatment compared with the SHAM trials (P < .001), no changes in sprint performance were observed after either the IPC or SHAM condition over 10m (IPC Δ < 0.01 [0.02]s, SHAM Δ < 0.01 [0.02]s) or 20m (IPC Δ = -0.01 [0.03]s, SHAM Δ < 0.01 [0.03]s) compared with control. Thus, an IPC protocol does not improve 10- or 20-m sprint performance in sprint-trained athletes.

Acute lung injury induced by intestinal ischemia and reperfusion is altered in obese female mice

RationalAcute lung injury (ALI) is a common complication after intestinal ischemia and reperfusion (I/R) injury that can lead to acute respiratory distress syndrome (ARDS). We have previously demonstrated that females are protected against lung damage induced by intestinal I/R through an estrogen mediated mechanism. ObjectivesTo investigate the effect of obesity on ALI induced by intestinal I/R in female mice. MethodsC57Bl/6 female mice were fed with a standard low-fat diet (SD) or a high-fat diet (HFD) for 9 weeks. Intestinal I/R injury was induced by a 45 min occlusion of the mesenteric artery followed by 2 and 24 h of reperfusion. ResultsSignificant increase in lung myeloperoxidase expression (MPO) and neutrophil numbers of SD and HFD mice occurred at 2 h and 24 h of reperfusion. Furthermore, HFD mice presented a significant increase in lung eosinophil peroxidase (EPO) expression and eosinophil numbers compared to SD mice. Lung wet/dry weight ratio was significantly greater in HFD mice at 2 and 24 h of reperfusion, accompanied by a significant increase in the expression of inducible NO in the lung tissue and a significant decrease in arterial oxygen saturation at 24 h of reperfusion relative to SD mice. ConclusionObesity predisposes female mice to increased pulmonary oedema and deterioration in gas exchange, which is accompanied by an increase in iNOS expression in the lung.

Flow-mediated slowing of brachial-radial pulse wave velocity: Methodological aspects and clinical determinants

BackgroundRecent studies proposed that deceleration in pulse wave velocity (PWV) following reactive hyperaemia might reflect arterial distensibility and endothelial function. We therefore investigated methodological aspects and clinical determinants of new indexes of flow-mediated slowing (FMS) of PWV in a community-based sample. MethodsIn 71 subjects (mean age, 60.3 years; 50.7% women), we continuously assessed brachial-radial PWV using Vicorder® at baseline and after 3-min or 5-min suprasystolic upper-arm cuff occlusion. We calculated the relative change (Δ) in PWV per each 30 s intervals during 4 min of post-occlusion. We performed stepwise regression analyses to assess determinants of the PWV response. ResultsThe peak FMS was detected at the first PWV recording obtained after occlusion. Overall, the decline in PWV during hyperaemia was significantly greater after 5-min of occlusion as compared to 3-min (effect sizes for 0–240 s intervals: −1.83% to −9.63%; P ≤ 0.037). PWV declined significantly less with higher age during the 0–60 s post-occlusion intervals (P ≤ 0.0053). On the other hand, after 120 s of post-occlusion, ΔPWV remained significantly lower in subjects with high diastolic blood pressure and oxidized LDL, and in smokers (P ≤ 0.028). Consequently, as compared to healthy reference group, participants with cardiovascular risk factors exhibited a delay in age-adjusted recovery of PWV after 5-min of occlusion (P ≤ 0.039). ConclusionsOur findings confirm the use of a 5-min occlusion time for the assessment of vasomotor function by FMS. Whereas the early FMS response might deteriorate with ageing, cardiovascular risk factors such as smoking, oxidative stress and hypertension might affect recovery of PWV after reactive hyperaemia.

A single electrical pulse within the protective zone of each cardiac cycle prevented reperfusion-induced ventricular tachycardia in conscious mice.

Early pioneering investigators discovered, in anesthetized dogs, a protective period within the cardiac cycle. The protective period was a time within the cardiac cycle when a precisely timed stimulus prevented the initiation of ventricular fibrillation caused by an earlier stimulus. Thus, in addition to the susceptible period of repolarization discussed by Wiggers and Wegria (Am. J. Physiol. 131:296, 1940; Am. J. Physiol. 128:500, 1940), there is also a nearby protective period. This report describes a protective period within the cardiac cycle of conscious mice when a precisely timed stimulus prevented the initiation of ventricular tachycardia caused by an earlier stimulus. In addition, we tested the hypothesis that this precisely timed pulse within the protective period prevents reperfusion‐induced ventricular tachyarrhythmias in conscious mice. Mice (n = 6) were prepared to record arterial blood pressure and the electrocardiogram. In addition, a vascular occluder was placed around the left main coronary artery, and stimulating electrodes were secured onto the left ventricle. A single precisely timed electrical pulse (5 msec pulse width and 2.5 V) to the left ventricle arriving 13.9 ± 1.1 msec after the R‐wave, caused ventricular tachycardia occurring 24.9 ± 0.9 msec after the R‐wave. Importantly, a second precisely timed electrical pulse arriving 18.8 ± 0.5 msec after the first stimulus blocked the induction of ventricular tachycardia caused by the earlier stimulus. On an alternate day, the susceptibility to sustained ventricular tachycardia produced by 3.5 min of occlusion and reperfusion of the coronary artery was determined in conscious mice by use of the vascular occluder. Reperfusion resulted in ventricular tachycardia in all six mice. A precisely timed pulse within the protective period prevented ventricular tachycardia in all mice.