Silicone-covered biodegradable magnesium stent for treating benign esophageal stricture in a rabbit model

BACKGROUND Stent insertion can effective alleviate the symptoms of benign esophageal strictures(BES).Magnesium alloy stents are a good candidate because of biological safety,but show a poor corrosion resistance and a quick loss of mechanical support in vivo.AIM To test the therapeutic and adverse effects of a silicone-covered magnesium alloy biodegradable esophageal stent.METHODS Fifteen rabbits underwent silicone-covered biodegradable magnesium stent insertion into the benign esophageal stricture under fluoroscopic guidance(stent group).The wall reconstruction and tissue reaction of stenotic esophagus in the stent group were compared with those of six esophageal stricture models(control group).Esophagography was performed at 1,2,and 3 weeks.Four,six,and five rabbits in the stent group and two rabbits in the control groups were euthanized,respectively,at each time point for histological examination.RESULTS All stent insertions were well tolerated.The esophageal diameters at immediately,1,2 and 3 wk were 9.8±0.3 mm,9.7±0.7 mm,9.4±0.8 mm,and 9.2±0.5 mm,respectively(vs 4.9±0.3 mm before stent insertion;P<0.05).Magnesium stents migrated in eight rabbits[one at 1 wk(1/15),three at 2 wk(3/11),and four at 3 wk(4/5)].Esophageal wall remodeling(thinner epithelial and smooth muscle layers)was found significantly thinner in the stent group than in the control group(P<0.05).Esophageal injury and collagen deposition following stent insertion were similar and did not differ compared to rabbits with esophageal stricture and normal rabbits(P>0.05).CONCLUSION Esophageal silicone-covered biodegradable magnesium stent insertion is feasible for BES without causing severe injury or tissue reaction.Our study suggests that insertion of silicone-covered magnesium esophageal stent is a promising approach for treating BES.

Evaluation of a rabbit rectal VX2 carcinoma model using computed tomography and magnetic resonance imaging

AIM： To establish a rabbit rectal VX2 carcinoma model for the study of rectal carcinoma.METHODS： A suspension of VX2 cells was injected into the rectum wall under the guidance of X-ray fluoroscopy. Computed tomography （CT） and magnetic resonance imaging （MRI） were used to observe tumorgrowth and metastasis at different phases. Pathological changes and spontaneous survival time of the rabbits were recorded.RESULTS： Two weeks after VX2 cell implantation, the tumor diameter ranged 4.1-5.8 mm and the success implantation rate was 81.8%. CT scanning showed low-density loci of the tumor in the rectum wail, while enhanced CT scanning demonstrated a symmetrical intensification in tumor loci. MRI scanning showed alow signal of the tumor on T1-weighted imaging anda high signal of the tumor on T2-weighted imaging.Both types of signals were intensified with enhanced MRI. Metastases to the liver and lung could beobserved 6 wk after VX2 cell implantation, and a largearea of necrosis appeared in the primary tumor. The spontaneous survival time of rabbits with cachexia and multiple organ failure was about 7 wk after VX2 cell implantation.CONCLUSION： The rabbit rectal VX2 carcinoma model we established has a high stability, and can be used in the study of rectal carcinoma.

Sodium hydroxide-induced esophageal stricture via an endoscopic injection needle: a novel rabbit model of corrosive injury

Purpose: Benign strictures of the esophagus are commonly encountered in clinical practice and are difficult to manage conservatively. This study aimed to establish a novel animal model of benign esophageal stricture by using corrosive-induced injury in rabbits with an injection of sodium hydroxide(NaOH) via a self-made endoscopic injection needle. Materials and Methods: Corrosive injury of the esophagus was induced in 10 rabbits by administration of 1 mL of 1.5% NaOH using a laryngoscope with a self-made endoscopic injection needle. The self-made injection needle was fabricated by modification of the core of an endoscopic injection needle. The laryngoscope examination was performed at 2 weeks and 4 weeks after induction of corrosive injury; esophagography was also performed at 4 weeks to assesse sophageals tricture.A lla nimalsw eree uthanizedat th een dof the fourth week; the esophagus was removed, and stained sectionsw eree xaminedm icroscopically. Results: Laryngoscope examination at 2 weeks showed ulceration. At the end of fo urth we e k,laryngosco py,r a diolo gical, and gross exa m inations showed successful in ductionof e s ophagea l stric turein a llanimal s,without any c omp licatio n.The m eanst r ic t ure inde x at the en dof fourth week wa s49.54±3. 61%; the mean le ngth of stricture w as18.0± 2.5mm.Micros copicexa mina tionrevea ledf ocalulceratio nand subm ucosalth i cke ning secondary to fibrosis. Conclusion:Rab bit esop hageal stri ctu re induced us ing lary ngosc opy with endosco pic injec tion of a sm all am ount of lowcon centration s odium hyd roxid e is a t echn ica lly simp le,safe,and re produ cible meth od for cre atio n of an animal m odel of esophageal stricture.This model can be useful for developing new treatment methods for esop hageal s tricture.

Analysis on characteristics of aerosol absorption and scattering over Zhangye, China

The first China-US joint dust field experiment was carried out by Lanzhou University, Chinese Academy of Sciences, China Me- teorological Administration, and University of Maryland, the Department of Energy （DOE）, USA, from April to June, 2008. The observation sites are located at Zhangye National Climatological Observatory, Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL）, and Jingtai with the Mobile Facilities of SACOL. The measurements of Particle Soot Absorp- tion Photometer and TSI Integrating Nephelometer are used to analyze the aerosol absorption and scattering characteristics over Zhangye. The results are： the aerosol absorption, total scattering, and backscattering coefficients present similar diurnal variation trends with their bi-peaks at 08：00 and 22!00, and they are generally higher in nighttime than in daytime. Their monthly average coefficient is the highest in April, and the!l drops in succession in May and June. Frequency analysis of aerosol single scattering albedo （SSA） shows that the magnitudes＇0f SSA at 450, 550, and 700 nm are mainly within 0.7q3.9. The maximum frequency of SSA at 450 and 700 nm distribute at 0.8, and at 0.85 for 550 nm. The averages of SSA at 450, 550, and 700 nm are 0.72, 0.75, and 0.68, respectively.