Objective To detect the effect of chitosan gel on rectal injury which was induced by acetic acid. Methods 36 rats were anesthetized, 4% acetic acid swab was placed into the rectum (3 cm in depth for 1 min) to establish rectum injury model. These rats were divided into model control group, positive control group and drug group with 12 rats each group randomly. Chitosan gel was given to the drug group through anus with the dose of 1 575 mg·kg-1 , and hemorrhoid cream (1 575 mg·kg-1 ) was administered in the positive control group for 6 successive days. At 30 min, 1, 4, 6 day( s) after administration, 3 rats of each group were sacrificed, and were dissected, rectal injury and rectal pathology morphology changing of each group at different time points of administration were compared through visual observation. Results At 30 min, 1, 4, and 6 day(s) after administrating chitosan gel, score of rectum mucosa injury in dury group was lower than those in model control and positive control group. Pathological changes ( including epithelial tissue necrosis, mesenchyme hyperemia, hemorrhage, edema, gland injury, infiltration of inflammatory cells) were significantly slighter in drug group than in model control group and positive control group. Those lesions were restored faster in drug group than in model control group and positive control group, and there was no obvious scar. Conclusion Chitosan gel can obviously alleviate the rectal injury caused by 4% acetic acid and has therapeutic effect.

Objective To establish a reproducible rat model of acute rectal mucosal injury induced by acetic acid. Methods Fifteen healthy Sprague-Dawley rats were randomly divided into the control group (3 rats) and experimental group (12 rats).Acute rectal mucosal injury was induced by 4%acetic acid using a cotton swab inserted into the rat rec-tum for 1 min to a depth of 3 cm.The morphological characteristics were analyzed by the naked eye and histology at 0.5 h and 1, 4, and 6 days after acetic acid intervention.Results All rats survived 6-day study period.The successful rate of model establishment was 100%.From 0.5 h to 1st day after acetic acid intervention, the gross morphology of recta showed congestion, edema and ulcer to ulcer complicated with hemorrhage.The histology showed necrosis and hemorrhage of the epithelial tissue of the mucosa to complete and extensive necrosis of the mucosa.The glandular structure showed partial to complete loss.The submucosa showed edema to edema complicated with hemorrhage and congestion.The interstitial tissues showed vasodilatation and congestion to inflammatory cell invasion.From 4 to 6 days after acetic acid intervention, the rectal mucosal changes were obviously improved.Epithelial and glandular regeneration and inflammatory granulation occurred, but not fully recovered, some edema and redness, partial lack of glands were still present.Conclusions 4%acetic acid for 1 min can be used to successfully induce rat model of acute rectal mucosal injury.This procedure is easy to operate, with a high success rate,reproducible, and the alterations are lasting more than 6 days.This animal model is very suitable for rapid screening of topical drugs for the treatment for rectal mucosal injury.

Objective To study the protective effect of vitamin C on UV-induced photoaged skin structure in rats and provide a basis for clinical medicine and health care.Methods Photoaging skin models were set up by chronic ultraviolet radiation in 24 SPF female Sprague-Dawley rats, irradiated twice weekly for 4 weeks.The rat photoaged skin was induced by exposure to a total dose of 123 J/cm2 UVA and 5 J/cm2 UVB for 4 weeks.Vitamin C was administered by gastric gavage in a dose of 50 mg/kg once daily for 30 days during the model development.We compared the pathological changes in the irradiated skin using HE, Masson’ s trichrome and Victoria blue B staining, and compared the ultrastructural changes by electron microscopy.Results Rat models with photoaged skin were developed successfully.The vitamin C group showed significant reduction of pathological severity including erythema, ulcers, epidermal cell proliferation, epidermal thickness, dermis vasodilation, inflammatory cell infiltration, fibroblast proliferation, endoplasmic reticulum dilatation, mitochondrial swelling and vacuolization, elastic fibers degeneration and focal accumulation, collagen fibers swelling with uneven thickness,compared with the rats of model group at the irradiation site.Conclusions Vitamin C is effective in reducing the structural damage of UV-induced photoaged skin in rats.

Objective To identify the risk factors associated with cardiovascular and cerebrovascular disease (CCVD) in maintenance hemodialysis (MHD) patients. Methods We analyzed all of the patients undergoing maintenance hemodialysis in the dialysis center of the 3rd Affiliated Hospital of Sun Yat-sen University for at least 3 months from Jan 1st, 2009 to Dec 31st, 2014. Baseline and yearly interval clinical data were recorded and patients were followed up until morbidity or death of CCVD. Cox proportional hazard regression and time-dependent Cox regression were used to estimate the relative risk of outcomes associated with clinical measurements. Results There were 243 patients enrolled in the study, with a mean age of (53.2 ± 16.4) years old, and 138 of them were male (56.8%). The multivariate Cox proportional model revealed that age (HR=1.040, 95%CI:1.015-1.065, P=0.002), Erythropoietin (EPO) dose (HR=0.914, 95%CI: 0.846-0.987, P=0.022) and history of cardiovascular and cerebrovascular disease (HR=4.045, 95%CI: 2.074-7.890, P<0.001) were independent predictors of CCVD in MHD patients. After adjusting for baseline predictors, time-dependent serum phosphorus level (HR=1.722, 95%CI: 1.034-2.866, P=0.037) was significantly associated with CCVD. Conclusion Older age, decreases in EPO dose and history of cardiovascular and cerebrovascular disease were associated with increased risks of CCVD in MHD patients. Increase in serum phosphorus level was associated with increased risks of CCVD in a time-dependent manner.