1.Role of hepatic macrophages in acute liver injury
Fangyan CHEN ; Yunwei HAO ; Weiran LIN ; Xu FAN ; Ying JIANG ; Fuchu HE
Military Medical Sciences 2014;(3):181-188
Objective To elaborate the role of hepatic inherent macrophages and monocyte-derived macrophages in acute liver injury.Methods A model of acute liver injury in mice was induced via intraperitoneally injection of CCl 4 .Af-ter CCl4 injection, analysis of the expression of CD45, F4/80, Ly6C and CD11b on the hepatic macrophage surface was performed by flow cytometry at 24, 48 and 72 h before the hepatic inherent macrophages (CD45+F4/80hi) and monocyte-de-rived macrophages ( CD45+F4/80 lo ) were sorted at the same time .The relative expression of cytokines in the two popula-tions of macrophages was detected by qRT-PCR.Results Compared with control , the number of total F4/80 +cells in the liver was markedly increased after CCl 4 injection, especially at 72 h.The number of CD45+F4/80lo cells increased signifi-cantly after CCl4 injection 24 h.The mRNA levels of MCP-1, TNF-α, TGF-β1, matrix metalloproteinase(MMP)-12 and MMP-13 were elevated significantly both in F 4/80 hi and F4/80 lo macrophages .IL-12βand IL-6 mRNA levels increased significantly only in F4/80hi macrophages, while the level of MMP-9 mRNA increased markedly only in F4/80lo macropha-ges.When compared with F4/80lo macrophages, MCP-1 and MMP-12 mRNA levels were elevated significantly , while the level of TNF-αmRNA decreased significantly in F4/80hi macrophages.Conclusion In acute liver injury, hepatic inherent macrophages and monocyte-derived macrophages both express inflammatory cytokines , promoting inflammation response and leading to liver damage .The ability to recruit inflammatory monocytes into the liver is much stronger ,the expression of in-flammatory cytokines ( IL-12βand IL-6 ) and MMP-12 is higher , but the expression of inflammatory cytokines ( TNF-α) MMP-9 is lower in hepatic inherent macrophages than in monocyte-derived macrophages .
2.Endoscopic ultrasound-guided fine needle aspiration with different needle types for solid pancreatic masses: a prospective and randomized comparative trial in two centers
Liang ZHONG ; Qi ZHU ; Tingting GONG ; Chen JIN ; Sijie HAO ; Tingjun YE ; Yunwei SUN ; Jihong TAN ; Lu XIA ; Dongxin ZHAO
Chinese Journal of Digestive Endoscopy 2012;29(7):364-369
Objective To compare the diagnostic yield of endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) for solid pancreatic masses performed with three different needle types through the cytological results.Methods All patients with solid pancreatic masses larger than 2cm from December 2010 to May 2011 were enrolled,and divided into two groups according to different access of EUS-FNA,trans-gastric approach with 19-,22-and 25-gauge needles (n =42) and trans-duodenal approach with 22-and 25-gauge needles (n =10).In both groups,EUS-FNA was performed with randomization of needle types.During the puncture,the suction,the number of movements,and the depth of insertion were fixed.At the end of the puncture,a liquid-based cytological (LBC) preparation was used to fix the specimen.One cytopathologists was assigned to make the diagnosis and comparison.Results Technical success was 100% and no procedure related complications occurred.No statistically significant differences were observed in different needles in terms of all cytological parameters between two groups (P > 0.05).However,the 25-gauge needle showed a trend towards a higher sensitivity,specificity,positive predictive value,negative predictive value and accuracy.Conclusion There is no significant difference in yield of cytological results between different needle types,although 25-gauge needle shows a relative superiority.
3.The effect of pressure therapy on the formation of hypertrophic scar and TGF-β1/Smad signaling pathway
Peng CAO ; Yunwei WANG ; Ming YAO ; Shaohui LI ; Yang CHEN ; Chan ZHU ; Qian LENG ; Liying REN ; Hao GUAN
Chinese Journal of Plastic Surgery 2022;38(7):804-813
Objective:To observe the effect of pressure therapy on the formation of hypertrophic scars(HTS) and transforming growth factor beta 1 (TGF-β1) / Sma and Mad homolog proteins (Smad) signaling pathway.Methods:Twelve adult healthy New Zealand white rabbits(provided by the Animal Experiment Center of the Air Force Military Medical University) were wounded with 1 cm round punch on 4 sites of the ventral side of each ear. Round scalpels were used to make incisions along the marked lines, dissect the skin and perichondrium. The remaining tissue was scraped off to expose the wound surface. Scar formation was observed on the 28th day after surgery. After the establishment of rabbit ear HTS models, the right ears were used as self-controls, while the left ears were set as the experimental group. Two hypertrophic scars were randomly selected from each rabbit ear, 24 per group. Experimental group: 4-0 nylon silk thread was used to sew the pressure pad on the circular NdFeB magnets pad with a diameter of 1.5 cm to the rabbit ear cartilage. Flexiforce pressure sensor was used to measure the pressure, and the pads were adjusted to maintain a pressure of 20-25 mmHg (1 mmHg=0.133 kPa) for more than 23 h per day. Control group: no treatment. On the 40th day of pressure therapy, the general morphology of rabbit ear scars were observed, and the tissues were harvested for hematoxylin and eosin (HE) staining and Masson’s Trichrome staining for histological study. The scar elevation index (SEI), the number of fibroblasts, and the thickness of the stratum corneum were calculated. The relative mRNA expression levels of TGF-β1, Smad3, collagen type (Collagen )Ⅰ, Collagen Ⅲ, α-smooth muscle actin (α-SMA) were measured with qPCR; Western blotting was used to detect the relative protein expression levels of TGF-β1, Collagen Ⅰ, Collagen Ⅲ, α-SMA and the phosphorylation level of Smad3 (the ratio of p-Smad3 and Smad3 proteins). Statistical analysis was performed with Excel 2019 and GraphPad Prism 8.0. The measurement data conformed to normal distribution and was expressed as Mean±SD. Student’s t-test was used for the comparison between two groups. P<0.05 was considered statistically significant. Results:A total of 96 wounds were formed in 12 rabbits, 27 wounds had no obvious hyperplasia, and the remaining 69 wounds formed hypertrophic scar tissue blocks with a prominent skin surface, firm texture, and dark red appearance. The scars formation rate was 71.9% (69/96). On the 40th day after the application of pressure, the scars in the experimental group were significantly reduced, softer, and the color was slightly lighter compared with the control group. The results of HE staining and Masson’s Trichrome staining showed that the thickness of the stratum corneum, SEI, and the number of fibroblasts were (69.33±6.03) μm, 1.30±0.08, and (236.30±14.64) cells/field, respectively, which were significantly lower than those in the control group [(114.00±10.15) μm, 1.72±0.05, (320.30±14.57) cells/field] (all P<0.01). Abundance in capillaries, inflammatory cells, and fibroblasts were not observed in the dermal layer. The collagen fibers were orderly arranged and sparse. The results of fluorescence quantitative PCR showed that the relative expression levels of TGF-β1, Smad3, Collagen Ⅰ, Collagen Ⅲ, and α-SMA mRNA in the experimental group were 0.48±0.08, 0.58±0.05, 0.04±0.01, 0.15±0.02, 0.31±0.03, respectively, lower than those of the control group(1.00±0.07, 1.00±0.05, 1.00±0.08, 1.00±0.10, 1.00±0.06) (all P<0.01). The results of Western blotting showed that the relative protein expression of TGF-β1, Collagen Ⅰ, Collagen Ⅲ, α-SMA and the phosphorylation level of Smad3 in the experimental group were 0.65±0.03, 0.07±0.01, 0.43±0.03, 0.53±0.03, 0.54±0.03, all lower than the control group’s 1.02±0.06, 0.93±0.05, 0.92±0.03, 0.82±0.03, 0.92±0.03 (all P<0.01). Conclusions:Pressure therapy can significantly inhibit the hyperplasia of scars, improve the structure of HTS tissue, facilitate the normal arrangement of collagen fiber, and reduce the excessive deposition of collagen. Pressure therapy may inhibit scar proliferation by regulating the TGF-β1/Smad signaling pathway.
4.The effect of pressure therapy on the formation of hypertrophic scar and TGF-β1/Smad signaling pathway
Peng CAO ; Yunwei WANG ; Ming YAO ; Shaohui LI ; Yang CHEN ; Chan ZHU ; Qian LENG ; Liying REN ; Hao GUAN
Chinese Journal of Plastic Surgery 2022;38(7):804-813
Objective:To observe the effect of pressure therapy on the formation of hypertrophic scars(HTS) and transforming growth factor beta 1 (TGF-β1) / Sma and Mad homolog proteins (Smad) signaling pathway.Methods:Twelve adult healthy New Zealand white rabbits(provided by the Animal Experiment Center of the Air Force Military Medical University) were wounded with 1 cm round punch on 4 sites of the ventral side of each ear. Round scalpels were used to make incisions along the marked lines, dissect the skin and perichondrium. The remaining tissue was scraped off to expose the wound surface. Scar formation was observed on the 28th day after surgery. After the establishment of rabbit ear HTS models, the right ears were used as self-controls, while the left ears were set as the experimental group. Two hypertrophic scars were randomly selected from each rabbit ear, 24 per group. Experimental group: 4-0 nylon silk thread was used to sew the pressure pad on the circular NdFeB magnets pad with a diameter of 1.5 cm to the rabbit ear cartilage. Flexiforce pressure sensor was used to measure the pressure, and the pads were adjusted to maintain a pressure of 20-25 mmHg (1 mmHg=0.133 kPa) for more than 23 h per day. Control group: no treatment. On the 40th day of pressure therapy, the general morphology of rabbit ear scars were observed, and the tissues were harvested for hematoxylin and eosin (HE) staining and Masson’s Trichrome staining for histological study. The scar elevation index (SEI), the number of fibroblasts, and the thickness of the stratum corneum were calculated. The relative mRNA expression levels of TGF-β1, Smad3, collagen type (Collagen )Ⅰ, Collagen Ⅲ, α-smooth muscle actin (α-SMA) were measured with qPCR; Western blotting was used to detect the relative protein expression levels of TGF-β1, Collagen Ⅰ, Collagen Ⅲ, α-SMA and the phosphorylation level of Smad3 (the ratio of p-Smad3 and Smad3 proteins). Statistical analysis was performed with Excel 2019 and GraphPad Prism 8.0. The measurement data conformed to normal distribution and was expressed as Mean±SD. Student’s t-test was used for the comparison between two groups. P<0.05 was considered statistically significant. Results:A total of 96 wounds were formed in 12 rabbits, 27 wounds had no obvious hyperplasia, and the remaining 69 wounds formed hypertrophic scar tissue blocks with a prominent skin surface, firm texture, and dark red appearance. The scars formation rate was 71.9% (69/96). On the 40th day after the application of pressure, the scars in the experimental group were significantly reduced, softer, and the color was slightly lighter compared with the control group. The results of HE staining and Masson’s Trichrome staining showed that the thickness of the stratum corneum, SEI, and the number of fibroblasts were (69.33±6.03) μm, 1.30±0.08, and (236.30±14.64) cells/field, respectively, which were significantly lower than those in the control group [(114.00±10.15) μm, 1.72±0.05, (320.30±14.57) cells/field] (all P<0.01). Abundance in capillaries, inflammatory cells, and fibroblasts were not observed in the dermal layer. The collagen fibers were orderly arranged and sparse. The results of fluorescence quantitative PCR showed that the relative expression levels of TGF-β1, Smad3, Collagen Ⅰ, Collagen Ⅲ, and α-SMA mRNA in the experimental group were 0.48±0.08, 0.58±0.05, 0.04±0.01, 0.15±0.02, 0.31±0.03, respectively, lower than those of the control group(1.00±0.07, 1.00±0.05, 1.00±0.08, 1.00±0.10, 1.00±0.06) (all P<0.01). The results of Western blotting showed that the relative protein expression of TGF-β1, Collagen Ⅰ, Collagen Ⅲ, α-SMA and the phosphorylation level of Smad3 in the experimental group were 0.65±0.03, 0.07±0.01, 0.43±0.03, 0.53±0.03, 0.54±0.03, all lower than the control group’s 1.02±0.06, 0.93±0.05, 0.92±0.03, 0.82±0.03, 0.92±0.03 (all P<0.01). Conclusions:Pressure therapy can significantly inhibit the hyperplasia of scars, improve the structure of HTS tissue, facilitate the normal arrangement of collagen fiber, and reduce the excessive deposition of collagen. Pressure therapy may inhibit scar proliferation by regulating the TGF-β1/Smad signaling pathway.
5.Effects of mechanical tension on the formation of hypertrophic scars in rabbit ears and transforming growth factor-β 1/Smad signaling pathway
Peng CAO ; Yunwei WANG ; Hao GUAN ; Yunshu YANG ; Shaohui LI ; Yang CHEN ; Chan ZHU ; Yu WAN ; Liying REN ; Ming YAO
Chinese Journal of Burns 2022;38(12):1162-1169
Objective:To explore the effects of mechanical tension on the formation of hypertrophic scars in rabbit ears and transforming growth factor-β 1 (TGF-β 1)/Smad signaling pathway. Methods:The experimental research method was adopted. Six New Zealand white rabbits, male or female, aged 3-5 months were used and 5 full-thickness skin defect wounds were made on the ventral surface of each rabbit ear. The appearance of all rabbit ear wounds was observed on post surgery day (PSD) 0 (immediately), 7, 14, 21, and 28. On PSD 28, the scar formation rate was calculated. Three mature scars in the left ear of each rabbit were included in tension group and the arch was continuously expanded with a spiral expander. Three mature scars in the right ear of each rabbit were included in sham tension group and only the spiral expander was sutured without expansion. There were 18 scars in each group. After mechanical tension treatment (hereinafter referred to as treatment) for 40 days, the color and texture of scar tissue in the two groups were observed. On treatment day 40, the scar elevation index (SEI) was observed and calculated; the histology was observed after hematoxylin eosin staining, and the collagen morphology was observed after Masson staining; mRNA expressions of TGF-β 1, Smad3, collagen Ⅰ, collagen Ⅲ, and α-smooth muscle actin (α-SMA) in scar tissue were detected by real-time fluorescence quantitative reverse transcription polymerase chain reaction; and the protein expressions of TGF-β 1, collagen Ⅰ, collagen Ⅲ, and α-SMA, and phosphorylation level of Smad3 in scar tissue were detected by Western blotting. The number of samples of each group in the experiments was 3. Data were statistically analyzed with independent sample t test. Results:On PSD 0, 5 fresh wounds were formed on all the rabbit ears; on PSD 7, the wounds were scabbed; on PSD 14, most of the wounds were epithelialized; on PSD 21, all the wounds were epithelialized; on PSD 28, obvious hypertrophic scars were formed. The scar formation rate was 75% (45/60) on PSD 28. On treatment day 40, the scar tissue of rabbit ears in tension group was more prominent than that in sham tension group, the scar tissue was harder and the color was more ruddy; the SEI of the scar tissue of rabbit ears in tension group (2.02±0.08) was significantly higher than 1.70±0.08 in sham tension group ( t=5.07, P<0.01). On treatment day 40, compared with those in sham tension group, the stratum corneum of scar tissue became thicker, and a large number of new capillaries, inflammatory cells, and fibroblasts were observed in the dermis, and collagen was more disordered, with nodular or swirling distribution in the scar tissue of rabbit ears in tension group. On treatment day 40, the mRNA expressions of TGF-β 1, Smad3, collagen Ⅰ, collagen Ⅲ, and α-SMA in the scar tissue of rabbit ears in tension group were respectively 1.81±0.25, 5.71±0.82, 7.86±0.56, 4.35±0.28, and 5.89±0.47, which were significantly higher than 1.00±0.08, 1.00±0.12, 1.00±0.13, 1.00±0.14, and 1.00±0.14 in sham tension group (with t values of 5.36, 9.82, 20.60, 18.26, and 17.13, respectively, all P<0.01); the protein expressions of TGF-β 1, collagen Ⅰ, collagen Ⅲ, and α-SMA, and phosphorylation level of Smad3 in the scar tissue of rabbit ears in tension group were respectively 0.865±0.050, 0.895±0.042, 0.972±0.027, 1.012±0.057, and 0.968±0.087, which were significantly higher than 0.657±0.050, 0.271±0.029, 0.631±0.027, 0.418±0.023, and 0.511±0.035 in sham tension group (with t values of 5.08, 21.27, 15.55, 16.70, and 8.40, respectively, all P<0.01). Conclusions:Mechanical tension can inhibit the regression of hypertrophic scars in rabbit ears through stimulating the hyperplasia of scars, inhibiting the normal arrangement of dermal collagen fibers, and intensifying the deposition of collagen fibers, and the mechanism may be related to the activation of TGF-β 1/Smad signaling pathway by mechanical tension.
6.Influences and mechanism of extracellular vesicles from dermal papilla cells of mice on human hypertrophic scar fibroblasts
Yunwei WANG ; Hao ZHANG ; Peng CAO ; Wanfu ZHANG ; Lin TONG ; Shaohui LI ; Yang CHEN ; Chao HAN ; Hao GUAN
Chinese Journal of Burns 2024;40(3):258-265
Objective:To investigate the influences and mechanism of extracellular vesicles from dermal papilla cells (DPC-EVs) of mice on human hypertrophic scar fibroblasts (HSFs).Methods:The study was an experimental research. The primary dermal papilla cells (DPCs) of whiskers were extracted from 10 6-week-old male C57BL/6J mice and identified successfully. The DPC-EVs were extracted from the 3 rd to 5 th passage DPCs by ultracentrifugation, and the morphology was observed through transmission electron microscope and the particle diameter was detected by nanoparticle tracking analyzer ( n=3) at 24 h after culture. The 3 rd passage of HSFs were divided into DPC-EV group and phosphate buffer solution (PBS) group, which were cultured with DPC-EVs and PBS, respectively. The cell scratch test was performed and cell migration rate at 24 h after scratching was calculated ( n=5). The cell proliferation levels at 0 (after 12 h of starvation treatment and before adding DPC-EVs or PBS), 24, 48, 72, and 96 h after culture were detected by using cell counting kit 8 ( n=4). The protein expressions of α-smooth muscle actin (α-SMA) and collagen typeⅠ (ColⅠ) in cells at 24 h after culture were detected by immunofluorescence method and Western blotting, and the protein expression of Krüppel-like factor 4 (KLF4) in cells at 24 h after culture was detected by Western blotting. After the 3 rd passage of HSFs were cultured with DPC-EVs for 24 h, the cells were divided into blank control group, KLF4 knockdown group, and KLF4 overexpression group according to the random number table. The cells in blank control group were only routinely cultured for 48 h. The cells in KLF4 knockdown group and KLF4 overexpression group were incubated with KLF4 knockdown virus for 24 h, then the cells in KLF4 knockdown group were routinely cultured for 24 h while the cells in KLF4 overexpression group were incubated with KLF4 overexpression virus for 24 h. The protein expressions of KLF4, α-SMA, and ColⅠ in cells were detected by Western blotting at 48 h after culture. Results:At 24 h after culture, the extracted DPC-EVs showed vesicular structure with an average particle diameter of 108.8 nm. At 24 h after scratching, the migration rate of HSFs in PBS group was (54±10)%, which was significantly higher than (29±8)% in DPC-EV group ( t=4.37, P<0.05). At 48, 72, and 96 h after culture, the proliferation levels of HSFs in DPC-EV group were significantly lower than those in PBS group (with t values of 4.06, 5.76, and 6.41, respectively, P<0.05). At 24 h after culture, the protein expressions of α-SMA and ColⅠ of HSFs in DPC-EV group were significantly lower than those in PBS group, while the protein expression of KLF4 was significantly higher than that in PBS group. At 48 h after culture, compared with those in blank control group, the protein expression of KLF4 of HSFs in KLF4 knockdown group was down-regulated, while the protein expressions of α-SMA and ColⅠ were both up-regulated; compared with those in KLF4 knockdown group, the protein expression of KLF4 of HSFs in KLF4 overexpression group was up-regulated, while the protein expressions of ColⅠ and α-SMA were down-regulated. Conclusions:The DPC-EVs of mice can inhibit the proliferation and migration of human HSFs and significantly inhibit the expressions of fibrosis markers α-SMA and ColⅠ in human HSFs by activating KLF4.
7.Applicability study of balloon pulmonary angioplasty in residual pulmonary hypertension of chronic thromboembolic pulmonary hypertension after pulmonary endarterectomy
Jinzhi WANG ; Xincao TAO ; Wanmu XIE ; Shuai ZHANG ; Zhu ZHANG ; Yunwei ZHAO ; Yishan LI ; Ana JIANG ; Hao WANG ; Qiang HUANG ; Zhenguo DI
Chinese Journal of Radiology 2024;58(3):318-323
Objective:To investigate the safety and efficacy of balloon pulmonary angioplasty (BPA) for residual pulmonary hypertension (PH) of chronic thromboembolic pulmonary hypertension(CTEPH) after pulmonary endarterectomy (PEA).Methods:Patients diagnosed as PH after PEA in China-Japan Friendship Hospital from Oct 2016 to Jun 2022 were included. The indication for BPA was decided on the basis of a consensus of the multi-disciplinary team for all patients with CTEPH. Before treatment, the patient′s exercise tolerance and pulmonary artery flow parameters were evaluated. A comparative analysis of various parameters before BPA treatment and at the last BPA was conducted. 6-min walk distance (6MWD) was analyzed using the paired Wilcoxon test; N-terminal pro-brain natriuretic peptide (NT-proBNP), mixed venous oxygen saturation, mean pulmonary arterial pressure (mPAP), cardiac index (CI) and pulmonary vascular resistance (PVR) were compared using the paired-samples t-test. WHO functional class was compared using McNemar′s test. Results:Twenty patients with a total of 130 vessels underwent 46 sessions of BPA treatment. The postoperative 6-minute walk distance (6MWD) [447 (415, 485) m] showed a significant improvement compared to the preoperative baseline [389 (335, 470) m] ( Z=6.52, P<0.05), Postoperative mixed venous oxygen saturation (72.0%±1.9%) showed a significant improvement compared to the preoperative levels (64.0%±2.7%) ( t=2.14, P<0.05).Postoperatively, plasma NT-proBNP [(351.9±129.9) pg/ml], mPAP [(24.2±1.9) mmHg], and PVR [(3.0±1.4) WU] significantly decreased compared to preoperative levels [(982.5±426.2) pg/ml, (33±2.1) mmHg, (8.0±1.6) WU)] ( t=3.38, 1.22, 2.10, P<0.05 for all). Postoperatively, there was a significant improvement in WHO functional class (Ⅰ,Ⅱ,Ⅲ,Ⅳ: 14, 4, 2, 0 cases) compared to preoperative status (Ⅰ,Ⅱ,Ⅲ,Ⅳ: 0, 13, 5, 2 cases) ( χ2=20.17, P<0.05). Four cases of pulmonary artery dissection and one episode of hemoptysis occurred postoperatively, with no other complications reported. Conclusions:BPA can significantly improve exercise tolerance and hemodynamic parameters for residual PH after PEA. BPA is a relatively safe and effective treatment for residual PH after PEA.
8.Berberine prevents primary peritoneal adhesion and adhesion reformation by directly inhibiting TIMP-1.
Xin LIU ; Yunwei WEI ; Xue BAI ; Mingqi LI ; Huimin LI ; Lei WANG ; Shuqian ZHANG ; Xia LI ; Tong ZHAO ; Yang LIU ; Rui GENG ; Hao CUI ; Hui CHEN ; Ranchen XU ; Heng LIU ; Yong ZHANG ; Baofeng YANG
Acta Pharmaceutica Sinica B 2020;10(5):812-824
Peritoneal adhesions are fibrous tissues that tether organs to one another or to the peritoneal wall and represent the major cause of postsurgical morbidity. Enterolysis at repeat surgeries induces adhesion reformation that is more difficult to prevent than primary adhesion. Here we studied the preventive effects of different approaches of berberine treatment for primary adhesion, and its effects on adhesion reformation compared to Interceed. We found the primary adhesion was remarkably prevented by berberine through intraperitoneal injection 30 min before abrasive surgery (pre-berberine) or direct addition into injured cecum immediately after the surgery (inter-berberine). Rats with adhesion reformation had a more deteriorative collagen accumulation and tissue injury in abrasive sites than rats with primary adhesion. The dysregulated TIMP-1/MMP balance was observed in patients after surgery, as well as adhesion tissues from primary adhesion or adhesion reformation rats. Inter-berberine treatment had a better effect for adhesion reformation prevention than Interceed. Berberine promoted the activation of MMP-3 and MMP-8 by directly blocking TIMP-1 activation core, which was reversed by TIMP-1 overexpression in fibroblasts. In conclusion, this study suggests berberine as a reasonable approach for preventing primary adhesion formation and adhesion reformation.