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1.
It had been proved that administration of sevoflurane for the first two minutes of reperfusion effectively protects the heart against reperfusion injury in rats in vivo.Our aim was to investigate the duration of effective sevoflurane administration and its underlying mechanism in isolated rat hearts exposed to global ischemia/reperfusion(I/R) injury.Adult male Sprague-Dawley rats were randomly divided into six groups(n=12):a sham-operation group,an I/R group,and four sevoflurane postconditioning groups(S2,S5,S10,and S15).In the S2,S5,S10,and S15 groups,the duration times of sevoflurane administration were 2,5,10,and 15 min after the onset of reperfusion,respectively.The isolated rat hearts were mounted on the Langendorff system,and after a period of equilibrium were subjected to 40 min global ischemia and 120 min reperfusion.Left ventricular(LV) hemodynamic parameters were monitored throughout each experiment and the data at 30 min of equilibrium and 30,60,90,and 120 min of reperfusion were analyzed.Myocardial infarct size at the end of reperfusion(n=7 in each group) and the expression of myocardial phosphorylated Akt(p-Akt) after 15-min reperfusion were determined in a duplicate set of six groups of rat hearts(n=5 in each group).Compared with the I/R group,the S5,S10,and S15 groups had significantly improved left ventricular end-diastolic pressure(LVEDP),left ventricular developed pressure(LVDP),and the maximal rate of rise or fall of the LV pressure(±dP/dtmax),and decreased myocardial infarct size(P<0.05),but not the S2 group.After 15 min of reperfusion,the expression of p-Akt was markedly up-regulated in the S5,S10,and S15 groups compared with that in the I/R group(P<0.05),but not in the S2 group.Sevoflurane postconditioning for 5 min was sufficient to activate Akt and exert maximal cardioprotection against I/R injury in isolated rat hearts.  相似文献   

2.
Background: Sevoflurane and propofol are effective cardioprotective anaesthetic agents, though the cardioprotection of propofol has not been shown in humans. Their roles and underlying mechanisms in anesthetic postconditioning are unclear.Mitochondrial permeability transition pore (MPTP) opening is a major cause of ischemia-reperfusion injury. Here we investigated sevoflurane- and propofol-induced postconditioning and their relationship with MPTP. Methods: Isolated perfused rat hearts were exposed to 40 min of ischemia followed by 1 h of reperfusion. During the first 15 min of reperfusion, hearts were treated with either control buffer (CTRL group) or buffer containing 20 μmol/L atractyloside (ATR group), 3% (v/v) sevoflurane (SPC group),50 μmol/L propofol (PPC group), or the combination of atractyloside with respective anesthetics (SPC ATR and PPC ATR groups). Infarct size was determined by dividing the total necrotic area of the left ventricle by the total left ventricular slice area (percent necrotic area). Results: Hearts treated with sevoflurane or propofol showed significantly better recovery of coronary flow,end-diastolic pressures, left ventricular developed pressure and derivatives compared with controls. Sevoflurane resulted in more protective alteration of hemodynamics at most time point of reperfusion than propofol. These improvements were paralleled with the reduction of lactate dehydrogenase release and the decrease of infarct size (SPC vs CTRL: (17.48±2.70)% vs (48.47±6.03)%,P＜0.05; PPC vs CTRL: (35.60±2.10)% vs (48.47±6.03)%, P＜0.05). SPC group had less infarct size than PPC group (SPC vs PPC:(17.48±2.70)% vs (35.60±2.10)%, P＜0.05). Atractyloside coadministration attenuated or completely blocked the cardioprotective effect of postconditioning of sevoflurane and propofol. Conclusion: Postconditioning of sevoflurane and propofol has cardioprotective effect against ischemia-reperfusion injury of heart, which is associated with inhibition of MPTP opening. Compared to propofol, sevoflurane provides superior protection of functional recovery and infarct size.  相似文献   

3.
Ischemic preconditioning and postconditioning distinctly attenuate ventricular arrhythmia after ischemia without affecting the severity of myocardial stunning. Therefore,we report the effects of sevoflurane preconditioning and postconditioning on stunned myocardium in isolated rat hearts. Isolated rat hearts were underwent 20 min of global ischemia and 40 min of reperfusion. After an equilibration period (20 min),the hearts in the preconditioning group were exposed to sevoflurane for 5 min and next washout ...  相似文献   

4.
The aim was to investigate how the PI3K/Akt pathway is involved in the protection of dexmedetomidine against propofol. The hippocampal neurons from fetal rats were separated and cultured in a neurobasal medium. Cell viability was assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Then neurons were pretreated with different concentrations of dexmedetomidine before 100 μmol/L propofol was added. Akt, phospho-Akt (p-Akt), Bad, phospho-Bad (p-Bad), and Bcl-xL were detected by Western blot. Also, neurons were pretreated with dexmedetomidine alone or given the inhibitor LY294002 before dexmedetomidine pretreatment, and then propofol was added for 3 h. The results demonstrated that propofol decreased the cell viability and the expression of p-Akt and p-Bad proteins, increased the level of Bad, and reduced the ratio of Bcl-xL/Bad. Dexmedetomidine pretreatment could reverse these effects. The enhancement of p-Akt and p-Bad induced by dexmedetomidine was prevented by LY294002. These results showed that dexmedetomidine potently protected the developing neuron and this protection may be partly mediated by the PI3K/Akt pathway.  相似文献   

5.
The use of mixed reality in science education has been increasing and as such it has become more important to understand how information is learned in these virtual environments. Spatial ability is important in many learning contexts, but especially in neuroanatomy education where learning the locations and spatial relationships between brain regions is paramount. It is currently unclear what role spatial ability plays in mixed reality learning environments, and whether it is different compared to traditional physical environments. To test this, a learning experiment was conducted where students learned neuroanatomy using both mixed reality and a physical plastic model of a brain (N = 27). Spatial ability was assessed and analyzed to determine its effect on performance across the two learning modalities. The results showed that spatial ability facilitated learning in mixed reality (β = 0.21, P = 0.003), but not when using a plastic model (β = 0.08, P = 0.318). A non-significant difference was observed between the modalities in terms of knowledge test performance (d = 0.39, P = 0.052); however, mixed reality was more engaging (d = 0.59, P = 0.005) and learners were more confident in the information they learned compared to using a physical model (d = 0.56, P = 0.007). Overall, these findings suggest that spatial ability is more relevant in virtual learning environments, where the ability to manipulate and interact with an object is diminished or abstracted through a virtual user interface.  相似文献   

6.
如今延长溶栓时间窗、减轻再灌注损伤是缺血性脑血管病亟待解决的的问题,缺血后适应提供了一种可能的解决方法,故成为研究的热点。缺血后适应通常指的是在组织缺血-再灌注之后进行的一系列短暂血管闭塞/血管再灌注,诱导组织针对缺血-再灌注损伤产生内源性保护作用,减少组织器官缺血-再灌注损伤。该文将综述缺血后适应脑保护的基本机制：减少缺血-再灌注后脑血流的改变,减少氧化应激产物的产生,抗炎,相关信号传导通路改变。  相似文献   

7.
Objective: In addition to pH regulation, Na+/H+ exchange (NHE) has been shown to facilitate cell growth and proliferation. However, the effects of long-term inhibition of Na+/H+ exchange on cardiac structural and functional remodeling post myocardial infarction (MI) are still controversial. The present study was therefore carried out to further investigate the effects of long-term treatment with cariporide, a specific inhibitor of NHE-1, on cardiac remodeling after MI in rats; Methods: Male Wistar rats that underwent coronary ligation were randomly selected for cariporide treatment starting 6 h after induction of MI or no treatment. Treatment was continued up to 6 weeks post MI, after which, the arterial, venous and left ventricular catheters were chronically implanted. Twenty-four h later, after hemodynamic signals were recorded in conscious rats, they were sacrificed and hearts were taken out for morphological examinations; Results: Cariporide treatment decreased the heart weight and heart weight to body weight ratio (bothP<0.05), decreased left ventricular end-diastolic pressure (P<0.001), improved myocardial contractility (dP/dt max) (P<0.05) and tended to increase the survival of treated rats compared to that of untreated infarct rats; Conclusion: The results of the present study indicate that the long-term inhibition of NHE with cariporide can attenuate cardiac structural remodeling and improve left ventricular dysfunction in infarcted rats, and suggest that Na+/H+ exchange inhibition could be an effective therapeutic strategy for myocardial infarction-induced heart failure.  相似文献   

8.
By design or default, anatomy educators are often responsible for introducing students to medical professionalism. Although much has been said about the role of anatomical education, there are no published reports suggesting how to measure change. This study investigated what professionalism attitudes, if any, change during a gross anatomy course. Additionally, the influence of four dichotomous variables related to student identity and preparation for medical school were analyzed for their effect on professionalism attitudes. A cross‐sectional time‐one (T1; beginning of the course), time‐two (T2; end of the course) study using the Penn State College of Medicine Survey of Professionalism was conducted. A multivariate analysis of variance identified the main effects and interaction effects of categorical variables. A Mann Whitney U test verified significant differences. This study found a reprioritization of professionalism attitudes in favor of altruism (P = 0.04 with a Cohen's d = 0.26) at T2. Female students (P = 0.03, Cohen's d = 0.38) and students from a science background (P = 0.04, Cohen's d = 0.36) changed the most in favor of altruism. Interestingly, though several factors correlated with dissimilarities in professionalism values at T1, gender was the only factor to show a significant difference in professionalism attitudes at T2. This cohort of students reported a statistically significant increase in altruism and no significant decreases in other professionalism attitudes concurrent with the gross anatomy course. Anat Sci Educ 3:12–16, 2010. © 2009 American Association of Anatomists  相似文献   

9.
The novelty of three-dimensional visualization technology (3DVT), such as virtual reality (VR), has captured the interest of many educational institutions. This study’s objectives were to (1) assess how VR and physical models impact anatomy learning, (2) determine the effect of visuospatial ability on anatomy learning from VR and physical models, and (3) evaluate the impact of a VR familiarization phase on learning. This within-subjects, crossover study recruited 78 undergraduate students who studied anatomical structures at both physical and VR models and were tested on their knowledge immediately and 48 hours after learning. There were no significant differences in test scores between the two modalities on both testing days. After grouping participants on visuospatial ability, low visuospatial ability learners performed significantly worse on anatomy knowledge tests compared to their high visuospatial ability counterparts when learning from VR immediately (P = 0.001, d = 1.515) and over the long-term (P = 0.003, d = 1.279). In contrast, both low and high visuospatial ability groups performed similarly well when learning from the physical model and tested immediately after learning (P = 0.067) and over the long-term (P = 0.107). These results differ from current literature which indicates that learners with low visuospatial ability are aided by 3DVT. Familiarizing participants with VR before the learning phase had no impact on learning (P = 0.967). This study demonstrated that VR may be detrimental to low visuospatial ability students, whereas physical models may allow all students, regardless of their visuospatial abilities, to learn similarly well.  相似文献   

10.
Since its advent word processing has become a common writing tool, providing potential advantages over writing by hand. Word processors permit easy revision, produce legible characters quickly, and may provide additional supports (e.g., spellcheckers, speech recognition). Such advantages should remedy common difficulties among weaker writers/readers in grades 1–12. Based on 27 studies with weaker writers, 20 of which were not considered in prior reviews, findings from this meta-analysis support this proposition. From 77 independent effects, the following average effects were greater than zero: writing quality (d = 0.52), length (d = 0.48), development/organization of text (d = 0.66), mechanical correctness (d = 0.61), motivation to write (d = 1.42), and preferring word processing over writing by hand (d = 0.64). Especially powerful writing quality effects were associated with word processing programs that provided text quality feedback or prompted planning, drafting, or revising (d = 1.46), although this observation was based on a limited number of studies (n = 3).  相似文献   

11.
The authors conducted a meta‐analysis and systematic review that examined 23 studies evaluating the effectiveness of child centered play therapy (CCPT) conducted in elementary schools. Meta‐analysis results were explored using a random effects model for mean difference and mean gain effect size estimates. Results revealed statistically significant effects for outcome constructs, including externalizing problems (d = 0.34), internalizing problems (d = 0.21), total problems (d = 0.34), self‐efficacy (d = 0.29), academic (d = 0.36), and other behaviors (d = 0.38). Further, a systematic review was conducted on all studies compared with Outcome Research Coding Protocol criteria. Results indicated that CCPT studies provided quantitative support and qualitatively promising to strong evidence in support of its use in the schools.  相似文献   

12.
Let Γd2nbe the set of trees with a given diameter d having a perfect matching,where 2n is the number of vertex.For a tree T in Γd2n,let Pd+1be a diameter of T and q = d m,where m is the number of the edges of perfect matching inPd+1.It can be found that the trees with minimal energy in Γd2nfor four cases q = d 2,d 3,d 4,[d2],and two remarks aregiven about the trees with minimal energy in Γd2nfor2d 33q d 5 and [d2] + 1 q2d 33 1.  相似文献   

13.
This multiyear scale-up effectiveness study of Open Court Reading (OCR) involved approximately 4,500 students and more than 1,000 teachers per year in Grades K–5 from 49 elementary schools in seven districts across the country. Using a school-level cluster randomized trial design, we assessed the implementation and effectiveness of Open Court Reading over two years. Implementation study results demonstrated adequate to high levels of fidelity across the treatment schools. Intent-to-treat analyses revealed no statistically significant main effects on students’ reading performance in Year 1 and a small negative effect (d = – .09) in Year 2. There were positive impacts for particular subgroups, including kindergarten (d = .12) and Hispanic (d = .10) students in the first year. However, there were negative impacts for first grade (d = –.13), females (d = –.11), students who were not eligible for free or reduced-price lunch (d = –.19), and non-English language learners (d = –.10) in the second year of the study. Thus, relative to the “business-as-usual” reading curricula, no positive overall impacts of OCR and mixed impacts for student subgroups were found.  相似文献   

14.
Astragalus mongholicus (AM) derived from the dry root of Astragalus membranaceus Bge. var. mongolicus (Bge.) Hsiao is a widely used traditional Chinese medicine. The present study investigated the potential role of AM on renal fibrosis on a rat model of unilateral ureteral obstruction (UUO). We divided 48 Sprague-Dawley rats randomly into 4 groups: sham-operated group (Sham), untreated UUO group, AM-treated (10 g/(kg·d)) UUO group, and losartan-treated (20 mg/(kg·d)) UUO group as positive control. Haematoxylin & eosin (HE) and Masson staining were used to study the dynamic histological changes of the kidneys 7 and 14 d after operation. The expressions of fibronectin (FN), type I collagen (colI), hepatocyte growth factor (HGF), transforming growth factor-β1 (TGF-β1), and α-smooth muscle actin (α-SMA) were analyzed by real-time polymerase chain reaction (PCR), immunohistochemistry staining, and Western blot. Results show that, similar to losartan, AM alleviated the renal damage and decreased the deposition of FN and colI from UUO by reducing the expressions of TGF-β1 and α-SMA (P<0.05), whereas HGF increased greatly with AM treatment (P<0.05). Our findings reveal that AM could retard the progression of renal fibrosis. The renoprotective effect of AM might be related to inhibition of myofibroblast activation, inducing of HGF and reducing of TGF-β1 expression. Project (No. 30170437) supported by the National Natural Science Foundation of China  相似文献   

15.
The presentation of pre-sliced specimens is a frequently used method in the laboratory teaching of cross-sectional anatomy. In the present study, a new teaching method based on a hands-on slicing activity was introduced into the teaching of brain, heart, and liver cross-sectional anatomy. A randomized, controlled trial was performed. A total of 182 third-year medical students were randomized into a control group taught with the prosection mode (pre-sliced organ viewing) and an experimental group taught with the dissection mode (hands-on organ slicing). These teaching methods were assessed by testing the students' knowledge of cross-sectional specimens and cross-sectional radiological images, and analyzing students' feedback. Using a specimen test on three organs (brain, heart, and liver), significant differences were observed in the mean scores of the control and experimental groups: for brain 59.6% (±14.2) vs. 70.1% (±15.5), (P < 0.001, Cohen's d = 0.17); for heart: 57.6% (±12.5) vs. 75.6% (±15.3), (P < 0.001, d = 0.30); and for liver: 60.4% (±14.5) vs. 81.7% (±14.2), (P < 0.001, d = 0.46). In a cross-sectional radiological image test, better performance was also found in the experimental group (P < 0.001). The mean scores of the control vs. experimental groups were as follows: for brain imaging 63.9% (±15.1) vs. 71.1% (±16.1); for heart imaging 64.7% (±14.5) vs. 75.2% (±15.5); and for liver imaging 61.1% (±15.5) vs. 81.2% (±14.6), respectively. The effect sizes (Cohen's d) were 0.05, 0.23, and 0.52, respectively. Students in the lower tertile benefited the most from the slicing experiences. Students' feedback was generally positive. Hands-on slicing activity can increase the effectiveness of anatomy teaching and increase students' ability to interpret radiological images.  相似文献   

16.
Little research has examined factors influencing statistical power to detect the correct number of latent classes using latent profile analysis (LPA). This simulation study examined power related to interclass distance between latent classes given true number of classes, sample size, and number of indicators. Seven model selection methods were evaluated. None had adequate power to select the correct number of classes with a small (Cohen's d = .2) or medium (d = .5) degree of separation. With a very large degree of separation (d = 1.5), the Lo–Mendell–Rubin test (LMR), adjusted LMR, bootstrap likelihood ratio test, Bayesian Information Criterion (BIC), and sample-size-adjusted BIC were good at selecting the correct number of classes. However, with a large degree of separation (d = .8), power depended on number of indicators and sample size. Akaike's Information Criterion and entropy poorly selected the correct number of classes, regardless of degree of separation, number of indicators, or sample size.  相似文献   

17.
This study tested the hypothesized negative impact of cognitive test anxiety in the test preparation, performance, and reflection phases. Data available from the participants (n = 124) included test anxiety, study skills, perceived threat of tests, and performance attributions. Preparation phase data revealed, compared to their counterparts, that students with high-cognitive test anxiety reported lower study skills (d = 0.83), rated tests as more threatening (d = 1.18), and prepared less effective test notes. Performance phase effects revealed that the high-anxiety group performed worse on tests (d = 0.96) and reported higher levels of emotionality (d = 1.42). Test reflection phase reports demonstrated a relationship between cognitive test anxiety and helplessness attributions. The results are interpreted through a process model, proposing that cognitive test anxiety is associated with detrimental perceptions and behaviors in all phases of the learning–testing cycle.  相似文献   

18.
Abstract

A meta-analysis of vocabulary interventions in grades pre-K to 12 was conducted with 37 studies to better understand the impact of vocabulary on comprehension. Vocabulary instruction was found to be effective at increasing students' ability to comprehend text with custom measures (d = 0.50), but was less effective for standardized measures (d = 0.10). When considering only custom measures, and controlling for method variables, students with reading difficulties (d = 1.23) benefited more than three times as much as students without reading problems (d = 0.39) on comprehension measures. Gains on vocabulary measures, however, were comparable across reading ability. In addition, the correlation of vocabulary and comprehension effects from studies reporting both outcomes was modest (r = .43).  相似文献   

19.
In this study, we randomly assigned 69 Grade 4 students to a writing-to-learn treatment (n = 23), comparison (n = 23), or no-treatment control (n = 23). Treatment and comparison students completed a science experiment involving balance. During the experiment, treatment students wrote four short responses and an extended response to document their learning. To control for writing time, comparison students wrote four short responses and an extended response about topics other than balance. On a 20-item balance knowledge posttest, control outperformed treatment (d = 0.89) and comparison (d = 1.05) on the lowest level balance questions (Level 1). At the highest level questions, Levels 3 and 4, treatment (ds = 1.42 and 0.94) and comparison (ds = 1.62 and 1.37) outperformed control. There were no significant differences in total words written or level of balance understanding on a posttest written response. The performance of individual responders to treatment is also discussed.  相似文献   

20.
In the course of normal classroom lessons, 103 students (median 11.10 years) were asked to spend 15 min writing ‘anything you can think of’ about the number 50 on a blank page. The products were independently scored by 2 specialist art teachers and 2 specialist mathematics teachers on criteria relevant to their specialisations. Immediately before this task, however, half the students (depleted group) worked on difficult matching problems for 3 min, whereas controls worked on facile problems. Although volume of creative response appeared only marginally affected, depleted students were rated as lower on overall creativity (d?=?.8) by the arts teachers. The mathematics teachers also rated the depleted students as showing less quality in their work (d?=?.97). The depleted students cited fewer mathematical statements, but displayed more errors in statements they had written. The findings were interpreted in terms of ego depletion effects upon creativity.  相似文献   

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