| The relationship between folates and tumors has deeply attractedresearchers. At present, the relationship between folates and cancers ofcolorectal, breast, cervical etc. have been investigated comprehensivelyand deeply. However, there is less research about the relationship betweenfolates and esophageal cancer (EC).Yanting county in Sichuan Province is one of the areas with thehighest incidence of EC in China. The EC incidence here was up to 88/100000 in 2000, and it's mortality has been ranking first among local cancers.The EC incidence at Linnong village in Yanting was up to 126.85/100 000between 1998 and 2005. Folates deficiency may be one of the risk factorsof EC. There is no research on the relationship between folates and EC,and no epidemiological study about serum folates of EC patientsdomestically.Serum folate is one of common indices for evaluation of bodynutritional status of folats. The epidemiological study about serum folatesis important approach to investigate the relationship between folates andEC. Therefore, it is basic and premise for the study to develop a method foraccurate determination of serum folates.This project intended to improve microbiological assay, and todevelop a microbiological assay (MA) for detect serum folates accurately. And the method was applied to epidemiological study about serum folates,and to investigate primarily the relationship between folates and EC inYanting to give scientific evidence for EC prevention.The research was carried out from the following two parts:1. Improvement on microbiological assay of serum folatesOn the basis of methods of 96-well microtiter plates and glycerol-cryoprotected Lactobacillus casei (L.casei) proposed by Newman EM andHome DW, et al. to improve conventional MA, this project carded out twoaspects of improvement: a. To select the optimal culture concentrationand incubation time, and to establish a simple equation curve as workcurve as a result of higher precise (RSD5.6%), which altered the pastsituation about logarithm curve as work curve and poor precise(RSD15%). b. To investigate the effect of surface acting agent (SAA)Tween-80 on L.casei growth and quantitative analysis, and to increasetwice for the linear range (from 4.4×10-12～53×10-12 to 7.5×10-12～150×10-12g).On improveing it, the optimal conditions were as follows: culture ofdiluion 40-folds (1.3×107 cfu/ml), Vitamin Folic Acid Assay Broth with0.24%(w/v) Tween-80, anaerobic incubation of L.casei at 37℃for 22hours. On the optimal conditions, the work curve of culture turbidity (Avalue) to concentration for folates were linear range of 0.05～1.00μg/L(7.5×10-12～150×10-12g) with a correlation coefficient of 0.9997, and therecovery of folates was 105.4%～112.7%, and the minimum detectionconcentration was 0.03μg/L, and the intra-day and inter-day precise (RSD)were 5.6% and 3.3%, respectively. The nomal human and rats serumfolates detected by this improved method were 11.7±4.7μg/L and 58.6±11.0μg/L within nomal average range of serum folates in literatures,respectively. Therefore, it is feasible of this improved method to detect serum folates, and it can be applied to case-control study on serum folateslevel of EC patients in Yanting.2. Case-control study on serum folates level of EC patientsin YantingTo collect serum of EC patients and nomal control subjects in Yanting,and to detect folates with the improved microbiological assay, and to usecase-control study to investigate the relationship between serum folates ofresidents in Yanting and EC. By Paired-Samples T Test, it showed thatserum folates level of EC patients (6.4±3.7μg/L) was significant lower thanthat of nomal control subjects (8.0±5.6μg/L, P＜0.05), which indicated thatthe serum folats was associated with EC in Yanting, and the lower serumfolates may be one of risk factors of development of EC in Yanting.This project determinated serum folates of EC patients with theimproved microbiological assay, and primarily investigated the relation-ship between serum folates and EC in Yanting to give scientific evidencefor EC prevention. |
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