Clinically, patients with various organ tumors often experience acute renal failure after surgery, which is among the most important causes of death after tumor surgery. The choice of effective drugs for preventing and treating acute renal failure and reducing the mortality rate of patients after tumor surgery has been widely examined. Renal ischemia-reperfusion injury (IRI) is one of the common causes of acute renal failure [1]. The kidney is an organ exhibiting high blood perfusion [2] and is very sensitive to ischemia. Excess oxygen free radicals during reperfusion further damage the renal tissue [3]. In addition to its lipid-lowering effect, probucol has antiinflammatory, anti-oxidative, and other effects. Our previous studies confirmed that probucol has a protective effect in rats with doxorubicin nephropathy [4–5]. This study examined whether the drug also has protective effects in rats with IRI-induced acute renal failure.

Materials and methods

Experimental animals

Forty healthy male Sprague-Dawley (SD) rats weighing 180–220 g were provided by the Animal Experimental Center of Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China (Experimental Animal Production License No.: SYXK (E) 2014-0046).After feeding for one week in separate cages at room temperature, urinary protein test results were all negative.

Drugs and reagents

The probucol tablets (Changtai) were produced by Chengde Jing Fu Kang Pharmaceuticals Co., Ltd. (China).The strength was 0.25 g/tablet and the lot number was 070801. Serum superoxide dismutase (SOD, lot No.080323) and malondialdehyde (MDA, lot No. 080214)detection kits were purchased from Wuhan Kerui Biotech Co., Ltd. (Wuhan, China).

Grouping and model preparation

Forty rats were randomly divided into the sham operation group [S group; body weight (205 ± 8.1) g],ischemia-reperfusion group [IR group; body weight (207± 9.3) g], probucol low-dose treatment group [probucol+ IR 1 group, P + IR 1 group; body weight (208 ± 7.9) g],and probucol high-dose treatment group [P + IR 2 group;body weight (207 ± 6.5) g]. Rats in the S and IR groups were intragastrically administered warm water daily.The P + IR 1 group was intragastrically administered probucol 250 mg/(kg•d), and the P + IR 2 group was intragastrically administered probucol 500 mg/(kg•d). IRI rat models were prepared after 1 week. The four groups of rats were fasted for 12 h before surgery. Anesthesia was performed by intraperitoneal injection of 3.5% chloral hydrate (l mL/100 g). An incision was made on the lower abdomen along the midline through the xiphoid process,the right kidney was exposed, and the right kidney vein was punctured to collect blood, after which the right kidney was excised. For the S group, only excision of the right kidney and separation of the left renal artery and vein were performed, while the left renal artery was not clipped. The left kidney was exposed, and the left renal artery and vein were separated. The left renal artery was clipped with a non-invasive arterial clip, and the color of the kidney changed from bright red to dark red. After 30 min of ischemia, the arterial clip was released and the color of the kidney changed from dark red to bright red,indicating that reperfusion was successful and the model was successfully established [6]. Normal saline replacement was administered intraperitoneally, the wound was closed layer-by-layer and covered with wet gauze, and the abdominal cavity was closed.

Specimen collection

After the models were established, the S and IR groups were intragastrically administered warm water every day,and the P + IR 1 and P + IR 2 groups were intragastrically administered probucol every day for 1 week. Rats were individually fed in metabolic cages before and on days 1, 4, and 7 after modeling. The rats were fasted without water deprivation, and 24-h urine was collected. Blood was drawn from the caudal vein. On day 7, the blood and kidney tissue samples were taken from all rats. An abdominal incision was made to remove the kidneys under sterile conditions. A portion of renal tissue was washed with normal saline at 4 °C, weighed, and ground,and the homogenate was centrifuged at 4100× g and 4°C to obtain the supernatant for determination of SOD and MDA activity. The other part of the kidney tissue was examined under a light microscope to evaluate histomorphological changes.

Observation indicators

The kidneys were weighed, and the kidney index was calculated: (kidney weight / body weight) × 10–2. Urine test: 24-h urinary protein quantification and urinary N-acetyl-beta-D-glucosaminide (NAG) enzyme were tested by the Clinical Laboratory of Wuhan General Hospital of PLA, China.

考核还可以考虑一些其他方面，比如对参加机器人类大学生创新设计、学科竞赛等技能比赛的学生，应附加成绩以鼓励学生的创新活动，进而提高学生的创新能力。

As patients with advanced malignant tumors,particularly elderly patients, have reduced immune function and degenerative changes in the function of various organs, poor tolerance to surgery and acute renal failure after surgery are common. This is mainly because blood loss after surgery leads to effective circulating blood volume, microcirculation, renal ischemia, and hypoxia injury; vital organs of the body, including the kidneys, have reduced compensatory ability; and surgical wounds lead to increased oxidative stress and increased inflammatory reactivity. Studies have shown that for acute renal failure in elderly patients with malignant tumors,the risk of death is significantly increased. Therefore,effective measures must be taken to prevent and treat acute renal failure in patients after tumor surgery.

Probucol was used clinically as a lipid-lowering drug in the 1970s. In recent years, studies have shown that probucol also has good anti-oxidative stress, antiinflammatory, and endothelial function improvement effects. In this study, 24-h urinary protein, urinary NAGase, CysC, SCr, BUN, and other indicators were significantly elevated in rats after IRI, renal pathological lesions were evident, renal index deteriorated, and acute renal failure occurred. After treatment with low-dose and high-dose, the levels of MDA in the serum and renal tissue of the P + IR 1 and P + IR 2 groups were significantly decreased, and SOD activity was significantly increased(P ＜ 0.05). The drug improved oxidative stress in the kidneys and restored the balance between oxidation and anti-oxidation. In terms of renal function, 24-h urinary protein quantification, urine NAGase, CysC, SCr, BUN,and other indicators were significantly decreased (P＜ 0.05), indicating that renal failure was improved. In addition, renal pathological injury and the kidney index also significantly improved. These results demonstrate that probucol reduces acute renal failure. Our previous studies confirmed that heme oxygenase-1 (HO-1) has a protective effect on the kidneys in rats with chronic renal insufficiency [12], while probucol induces HO-1 expression and increases the activity of HO-1 [13], which may be another important mechanism in renal protection.

理论通常都是解释性、描述性的、抽象的概念居多，而学前教育专业存在着鲜明的实践性，幼儿教育中所有的实践活动都蕴含着教育学的理论，如果过于强调幼儿教育的理论性，我们就会忽视教育学与实际生活的密切联系。正如同学生走上工作岗位后会产生“理论无用”的错觉，这种理论与实践严重相脱离的观念在当今大多数高等院校频频出现，使大多数师生的创新能力受到阻碍，与当今创新人才观不符合。

Kidney morphology examination: Light microscopy:the kidney tissue was obtained, fixed with 10%formaldehyde solution, dehydrated conventionally,embedded with paraffin, and cut into 2–4-µm slices for hematoxylin and eosin (HE), Masson, and silver staining,and was observed under a regular light microscope and photographed with a professional camera.

The kidney is a high-blood-perfusion organ, whose blood flow accounts for 20%–25% of the blood flow in the body and is very sensitive to ischemia. Kidney IRI is one of the common causes of acute renal failure. The pathogenesis of renal IRI is complex and is currently thought to be mainly related to the following factors: renal cell apoptosis, oxidative stress response, inflammatory response, endothelial dysfunction, and impaired cellular energy metabolism [7–8]. Increased oxidative stress in the kidney is particularly critical. After IRI in the kidney,more oxygen radicals are produced through the xanthine oxidase pathway. Activated oxygen radicals act on the unsaturated fatty acids in the cell membrane of the kidney, resulting in lipid peroxidation and a large amount of MDA. MDA is a commonly used indicator that reflects the body’s lipid peroxide content and degree of attack by superoxide radicals [9]. SOD is a major antioxidant enzyme in the body and kidney tissues. It removes superoxide anions from the body, reduces oxidative stress damage in cells, and repairs damaged cells [10–11].

Statistical methods

The experimental results were expressed as the mean± the standard deviation (χ ± s). The measurement data of multiple groups were compared by analysis of variance and categorical data were compared using χ2 test with SPSS 11.3 software (SPSS, Inc., Chicago, IL, USA). The difference was considered statistically significant at P ＜0.05.

Results

General conditions of rats

Compared to the S group, rats in the IR, P + IR 1, and P + IR 2 groups showed gradually slowing reactions,reduced movement, crouching and arched back, poor hair color, reduced eating and drinking, edema in the lips and limbs, and an enlarged abdomen. In the P + IR 1 and P + IR 2 groups, 1 week after treatment with probucol,food and water intake improved, body weight began to increase, reactions improved, and edema decreased, but the values were still worse than those for the S group.There was no significant improvement in the IR group.

Blood test: Serum creatinine (SCr), blood urea nitrogen(BUN), and cystatin C (CysC) were measured 1 week after the models were established. Measurements were performed with an automatic biochemistry analyzer by the Clinical Laboratory of Wuhan General Hospital of PLA (China) and the average of two measurements was taken.

Changes in 24-h urinary protein and urinary NAG enzyme levels before and after treatment in all groups of rats

The 24-h urinary protein and urinary NAG enzyme levels in the IR, P + IR 1, and P + IR 2 groups were significantly higher than those in the S group after modeling (P ＜ 0.05). Compared to IR rats, the 24-h urinary protein and urinary NAG enzyme levels in the P + IR 1 and P + IR 2 groups were significantly reduced.The 24-h urinary protein and urine NAG enzyme levels in the P + IR 2 group were lower than those in the P + IR 1 group, but the difference was not significant (P ＞ 0.05;Tables 1–2).

Changes of blood biochemistry and kidney index in each group

The levels of CysC, SCr, and BUN in the P + IR 1 and P + IR 2 groups were significantly lower than those in the IR group (P ＜ 0.05). The levels of CysC, SCr, and BUN in the P + IR 2 group were lower than those in the P + IR 1 group, but the difference was not significant (P ＞ 0.05).The renal index level was significantly improved in the P + IR 1 and P + IR 2 groups compared to that in the IR group (Table 3).

Contents of SOD and MDA in the serum and kidney tissue of each group

The content of MDA in serum and renal tissue of the IR group was significantly increased, while the activity of SOD was significantly decreased. Compared to the IRgroup, the content of MDA in the serum and kidney tissue of the P + IR 1 and P + IR 2 groups decreased significantly,and SOD increased significantly (P ＜ 0.05). The content of MDA in the P + IR 2 group was lower than that in the P +IR 1 group and the SOD was increased, but the difference was not significant (P ＞ 0.05; Table 4).

Table 1 Comparison of 24-h urinary protein levels in each group mg)

Note: Compared to the value before modeling, a P ＜ 0.05; compared to the S group, b P ＜ 0.05; compared to the IR group, c P ＜ 0.05; compared to the P + IR 1 group, d P ＞ 0.05

Group (Number of animals) Before modeling 1 day after modeling 4 days after modeling 7 days after modeling S (10) 6.32 ± 1.27 6.45 ± 1.08 6.62 ± 1.35 6.62 ± 1.35 IR (10) 6.71 ± 1.85 182.12 ± 15.24ab 279.12 ± 19.61ab 373.12 ± 22.61ab P + IR 1 (10) 6.64 ± 1.57 132.36 ± 19.27abc 210.17 ± 13.26abc 302.38 ± 21.74abc P + IR 2 (10) 6.62 ± 1.43 125.65 ± 20.36abcd 203.45 ± 14.05abcd 294.45 ± 21.05abcd

Table 2 Comparison of urine NAG enzyme levels in each group , U/L)

Note: Compared to the value before modeling, a P ＜ 0.05; compared to the S group, b P ＜ 0.05; compared to the IR group, c P ＜ 0.05; compared to the P + IR 1 group, d P ＞ 0.05

Group (Number of animals) Before modeling 1 day after modeling 4 days after modeling 7 days after modeling S (10) 20.4 ± 2.3 20.7 ± 1.9 21 ± 2.4 22 ± 2.2 IR (10) 20.5 ± 2.1 49.1 ± 3.9ab 74.4 ± 4.3ab 90.4 ± 5.7ab P + IR 1 (10) 20.3 ± 2.4 40.5 ± 3.4abc 53.7 ± 4.1abc 76.1 ± 5.2abc P + IR 2 (10) 20.3 ± 2.2 38.6 ± 3.1abcd 49.1 ± 3.8abcd 72.5 ± 4.9abcd

Table 3 Effects on blood biochemistry and kidney index in each group

Note: Compared to the S group, a P ＜ 0.05; compared to the IR group, b P ＜ 0.05; compared to the P + IR 1 group, c P ＞ 0.05

Group (Number of animals) CysC (mg/L) BUN (mmol/L) SCr (mmol/L) Kidney index S (10) 0.87 ± 0.26 7.23 ± 1.13 57.38 ± 11.72 0.82 ± 0.35 IR (10) 4.68 ± 1.75a 10.58 ± 2.35a 146.13 ± 10.45a 1.26 ± 0.35a P + IR 1 (10) 3.01 ± 0.84ab 9.5 ± 1.22ab 102.35 ± 9.82ab 1.054 ± 0.43 P + IR 2 (10) 2.91 ± 0.73abc 9.4 ± 1.02abc 98.16 ± 9.74abc 1.04 ± 0.41abc

Table 4 SOD and MDA contents in the serum and kidney tissue of each group

Note: Compared to the S group, a P ＜ 0.05; compared to the IR group, b P ＜ 0.05; compared to the P + IR 1 group, c P ＞ 0.05

?

Changes of kidney pathomorphology in each group

1.3.2 临床严重性评分 治疗前后严格按照Wang等[9]的临床严重程度评分系统对每一位入组患儿进行临床严重程度（CS）评分，采用0-3分制进行评分， 即⑴呼吸：0分：＜30次/min，1分：31-45次/min，2 分：46-60 次/min，3 分：＞60 次/min；⑵喘息：0分：无，1分：呼吸终末或听诊器可闻及，2分：整个呼吸相或不用听诊器可闻及，3分：呼吸全程不用听诊器可闻及；⑶三凹征：0分：无，1分：仅见于肋间，2分：锁骨上可见，3分：伴严重鼻翼扇动；⑷一般情况：0分：正常，3分：厌食、烦躁、嗜睡。CS评分为各项总和，其中0-4分为轻度，5～8分为中度，9-12分为重度。

Fig. 1 Pathomorphological changes in the kidneys of rats in each group(×400). (a) HE staining of the S group;(b) Masson + silver staining of the S group; (c) HE staining of the IR group; (d)Masson + silver staining of the IR group;(e) HE staining of the P + IR 1 group; (f)Masson + silver staining of the P + IR 1 group; (g) HE staining of the P + IR 2 group; (h) Masson + silver staining of the P + IR 2 group

Discussion

为了确保钢筋笼的牢固性，技术人员应利用加强筋进行定位，使其成型均匀分布于截面中，并利用点焊成型的方法进行分节预制，保证单节的长度小于10m。钢筋的尺寸一般固定，下料时会出现长度不一的问题，且相邻主筋错开长度应不小于35d。因此在制作钢筋半成品后，审查人员应成批进行验收，并整齐堆放验收合格的钢筋笼，以免影响其他正常的施工工序。对于不合格产品应返工修补，之后再次审查，直至合格。除此之外，施工期间还应利用吊车下方钢筋笼，并利用分节安装的方法进行单面焊接，根据设计要求安装垫块。

了解美国学要从它的概念、特征、研究方法、理论等基础性工作入手。美国学这个概念在上世纪80年代初陆续出现在国内期刊上。例如，贺龙宝（1980）在《现代外国哲学社会科学文摘》上发表摘译文章“《美国学问题》论文集”；张宝训（1982）在《国外社会科学》刊登“苏联的美国学研究”编译稿；戴炜栋（1985）在《外语界》发表“记1984年美国学国际会议”等。

Serum and kidney tissue SOD and MDA detection: SOD activity and MDA content in the serum and kidney tissue were measured 1 week after the models were established.The specific procedures and calculation formulas were conducted according to the kit instructions, and the average of two measurements was taken.

In summary, when acute renal failure occurs after surgery for malignant tumors, probucol has good alleviation and treatment effects. The mechanism may involve lipid regulation, anti-oxidative stress, antiinflammation, endothelial function improvement, etc.Probucol shows potential for clinical application.

Conflicts of interest

Under light microscopy, the glomeruli, renal tubules,and interstitium were normal in the S group. The IR group was mainly characterized by renal tubular injury.HE staining showed slight hyperplasia of the glomerular mesangial matrix, widened renal interstitium infiltrated by a considerable volume of inflammatory cells, some atrophied renal tubules, and shedding tubular epithelial cells; a considerable volume of red blood cells and white blood cells in the renal interstitium, as well as blood stasis in the small interstitial blood vessels were observed.Masson + silver staining showed a focal distribution of interstitial fibrosis. The pathological changes of rats in the P + IR 1 and P + IR 2 groups were significantly lower than those in the IR group. The glomerular structure was relatively normal, and renal interstitial lesions were mild(Fig. 1).

The authors indicated no potential conflicts of interest.

References

1. Kers J, Leemans JC, Linkermann A. An overview of pathways of regulated necrosis in acute kidney injury. Semin Nephrol, 2016, 36:139–152.

2. Huo HC, Wang Q, Wang SL, et al. Expression changes of peroxiredoxin III in the myocardium of renal ischemia reperfusion injury model in rats. J Hebei Med Univ (China), 2016, 37: 1165–1169.

3. DoiK, Rabb H. Impact of acute kidney injury on distant organ function:recent findings and potential therapeutic targets. Kidney Int, 2016,89: 555–564.

4. Yang C, Lan TB. Study of protective effect and mechanism of probucol in rats with doxorubicin-induced nephropathy. Chin Pharmacist(China), 2011, 14: 769–771.

5. Yang C, Lan TB. Effect of probucol on cystatin C, renal function and renal pathology in experiment rat. Chin J Clinicians (Elect Edit)(China), 2011, 5: 2582–2586.

6. Lee HT, Kim M, Kim M, et al. Isoflurane protects against renal ischemia and reperfusion injury and modulates leukocyte infiltration in mice. Am J Physiol Renal Physiol, 2007, 293: F713–722.

7. Horvath G, Brubel R, Kovacs K, et al. Effects of PACAP on oxidative stress-induced cell death in rat kidney and human hepatocyte cells. J Mol Neurosci, 2011, 43: 67–75.

8. Hou SC, Gao JG, Li K. Role of Nrf2 in the process of L-carnitine attenuates renal ischemia-reperfusion injury. Chin J Nephrol (China),2014, 30: 60–61.

9. Kir HM, Sahin D, Oztas B, et al. Effects of single-dose neuropeptide Y on levels of hippocampal BDNF, MDA, GSH, and NO in a rat model of pentylenetetrazole-induced epileptic seizure. Bosn J Basic Med Sci,2013, 13: 242–247.

10. Lu Y, Zhang YY, Hu YC, et al. Protective effects of 2’,4’-dihydroxy-6’-methoxy-3’,5’-dimethylchalcone against hydrogen peroxide-induced oxidative stress in hepatic L02 cell. Arch Pharm Res, 2014, 37:1211–1218.

11. Badgujar PC, Chandratre GA, Pawar NN, et al. Fipronil induced oxidative stress involves alterations in SOD1 and catalase gene expression in male mice liver: Protection by vitamins E and C.Environ Toxicol, 2016, 31: 1147–1158.

12. Yang C, Liu XC, Lan TB. Immunohistochemistry and pathology of heme oxygenase-1 in the 5/6 nephrectomized rats. J Huazhong Univ Sci Tech (Health Sci)(China), 2004, 33: 158–164.

13. Deng YM, Wu BJ ,Witting PK, et al. Probucol protects against smooth muscle cell proliferation by upregulating heme oxygenase-1.Circulation, 2004, 110: 1855–1860.