木糖醇发酵动力学研究

根据通用的分批发酵动力学模型,建立了莫格假丝酵母由木糖转化为木糖醇的发酵动力学模型,用遗传算法估算反应动力学模型参数.计算结果表明,该模型能较好地与实验结果相吻合.     

Untersuchungen über den Mechanismus der Magenentleerung bei Mensch und Ratte nach oraler Applikation verschiedener Zucker

Zusammenfassung Die vorliegende Arbeit sollte die Beziehungen zwischen der Konzentration verschiedener Prüfsubstanzen (Glucose, Galaktose, Fructose, Saccharose, Maltose, Lactose, Sorbit, Xylit) und der Geschwindigkeit der Magenentleerung aufzeigen. Bei Untersuchungen an 912 Ratten konnte festgestellt werden, daß dem osmotischen Druck der verabreichten Lösungen eine bedeutsame Rolle bei der Regulierung der Magenentleerung zukommt. So ist die Magenentleerung bei Invertzucker gegenüber der bei Saccharose verzögert, da hier Glucose und Fructose in freier Form vorliegen und der osmotische Druck bei gleicher Konzentration der Lösungen infolgedessen doppelt so hoch ist. Warum die Disaccharide Maltose, Saccharose und Lactose eine langsamere Magenentleerung aufweisen als gleichprozentige Glucose-, Galaktose- und Sorbitlösungen, die einen doppelt so hohen osmotischen Druck haben, muß offenbleiben. Für sich allein betrachtet, folgt jedoch jeder Zucker der Regel, daß bei höherer Konzentration der Lösungen die Magenentleerung verzögert ist. — Außerdem erhielten 19 Probanden im Vorversuch 250 ccm Bariumsulfatlösung, im Hauptversuch bekam eine Gruppe 50 g Glucose, die andere Gruppe 100 g Glucose, gelöst in der gleichen Menge Kontrastbrei. Jeweils nach zwei Stunden wurden Röntgenaufnahmen des Magens gemacht und die Restfüllungen mit denen des Vorversuchs verglichen. Trotz starker Streuung der Einzelwerte war bei Zusatz von Glucose eine deutliche Verzögerung der Magenentleerung zu beobachten, die bei Gabe von 100 g Glucose signifikant größer war als bei Gabe von 50 g Glucose.

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Study of the evacuation mechanism of the stomach after oral administration of different sugars in man and rat

Summary It is the purpose of the present work to describe the relation between the concentration of different test-substances (glucose, galactose, fructose, saccharose, maltose, lactose, sorbitol and xylitol) and the speed of their evacuation from the stomach. Experiments with 912 rats showed that the osmotic pressure of the administered solution plays an important role in the regulation of the evacuation of the stomach. In accordance with these views, emptying of the stomach is more retarded after giving invert sugar than after saccharose at the same concentration, for the former has twice the osmotic pressure of the latter due to the disaccharide being completely hydrolyzed to glucose and fructose. The question remains open, however, why disaccharides like maltose, saccharose and lactose show a slower evacuation from the stomach than solutions of glucose, galactose or sorbitol at the same concentration, although the latter have twice the osmotic pressure. Viewed separately though, every sugar follows the rule that higher concentrations of the solutions slow down emptying of the stomach. — In a first experiment 19 subjects each received 250 ml of a solution of barium sulphate; later the subjects were divided into two groups, one receiving the same amount of the contrast medium as before but in addition 50 g of glucose, the second the contrast and 100 g of glucose. X-ray pictures of the stomach were taken after 2 h in each group and the amount of residual filling compared with that of the first experiment. In spite of considerable variation, there was a net slowing of stomach emptying, which was significantly greater after 100 g of glucose than after 50 g.

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Etude du mécanisme d'évacuation de l'estomac chez l'homme et le rat après administration orale de divers sucres

Résumé Le présent travail se propose de décrire les relations entre la concentration de différentes substances d'essai (glucose, galactose, fructose, saccharose, maltose, lactose, sorbitol, xylitol) et la vitesse d'évacuation de l'estomac. Au cours d'expériences sur 912 rats, on a pu constater que la pression osmotique des solutions administrées jouait un rôle important dans la régulation de l'évacuation de l'estomac. Ainsi, avec le sucre interverti, l'évacuation de l'estomac est retardée par rapport à celle observée avec le saccharose, car le glucose et le fructose se trouvent sous forme libre, et la pression osmotique pour une même concentration des solutions est, de ce fait, doublée. On ne sait pas pourquoi les disaccharides tels que le maltose, le saccharose et le lactose provoquent une évacuation de l'estomac plus lente que des solutions de même concentration de glucose, de galactose et de sorbitol, qui ont une pression osmotique deux fois plus élevé. Chaque sucre considéré séparément suit cependant la règle selon laquelle l'évacuation de l'estomac est retardée quand les solutions ont une concentration plus élevée. — En outre, 19 personnes ont reçu, au cours d'une épreuve préliminaire, 250 cm³ d'une solution de sulfate de baryum; au cours de l'épreuve principale, un groupe a reçu 50 g de glucose, et l'autre groupe 100 g de glucose, dilués dans la même quantité de bouillie opaque. Chaque fois, on a fait au bout de deux heures des radiographies de l'estomac et on a comparé les contenus restants avec ceux de l'épreuve préliminaire. Malgré une grande dispersion des valeurs isolées, on observait un net retard dans l'évacuation de l'estomac lors de l'administration de glucose; après administration de 100 g de glucose, ce retard était significativement plus grand qu'après administration de 50g.

     

Effects of xylitol and carbohydrate diets on dental caries, dentine formation and mineralization in young rats

Female Wistar rats were weaned at the age of 3 weeks and fed for 7 weeks either a high-sucrose diet, a non-cariogenic raw potato-starch diet, a high-sucrose diet with 5% xylitol supplement, a raw potato-starch diet with 5% xylitol supplement or a non-cariogenic, commercial, powdered rat food (Ewos R3) for reference. A low xylitol concentration reduced the progression and severity of carious lesions but did not affect dentine apposition or the width of predentine in rats fed high-carbohydrate diets. Widening of the predentine zone in rats fed a high-sucrose diet might reflect disturbed mineralization, which could not be explained by serum ionized calcium or phosphate ion levels and which could not be corrected by low xylotol concentrations. It is concluded that the reduced area of dentinal carious lesions after low xylitol supplementation is not dependent on dentine formation or mineralization, but rather on direct effects in the mouth.     

Effect of xylitol on dental plaque in vivo during carbohydrate challenge

Abstract – Xylitol has previously been shown to inhibit acid production in vitro when glucose is used as energy source, and the present studies were carried out to investigate whether this effect was valid in vivo. A solution containing both xylitol and glucose was applied on sucrose—induced 4-day-old plaque in vivo. The xylitol added to the glucose solution inhibited the acid production in the plaque, measured as a drop in pH, compared to using glucose alone. A further reduction in acidogenicity was obtained when xylitol was used as a rinse for 1 hr continuously prior to the glucose challenge.     

Uptake and expulsion of 14C-xylitol by xylitol-cultured Streptococcus mutans ATCC 25175 in vitro

Abstract— The effect of successive cultivations in the presence of 6% xylitol on the uptake and expulsion of ¹⁴C-xylitol was studied using the cells of Streptococcus mutans 25175. Three sequential cultivations did not alter the growth inhibition percentage (approximately 50%) observed in the presence of 6% xylitol. The ¹⁴C-xylitol uptake experiments performed with growing and resting cells showed that both the uptake and the expulsion of xylitol were enhanced by xylitol-culturing. Both xylitol-cultured and resting control cells contained only one major labeled compound which was identified as ¹⁴C-xylitol 5-phosphate. The label subsequently was expelled from the cells as ¹⁴C-xylitol. These results indicate that S. mutans possesses an intracelluiar xylitol cycle and this cycle is regulated by adding xylitol to the growth medium.     

Cariogenic traits in xylitol‐resistant and xylitol‐sensitive mutans streptococci

Long‐term xylitol consumption leads to the emergence of xylitol‐resistant (X‐R) mutans streptococci. The aim of the present study was to compare cariogenic traits in X‐R and xylitol‐sensitive (X‐S) strains. Six strains of mutans streptococci, three X‐R and three X‐S strains, were studied. Xylitol resistance and sensitivity were confirmed by growth in xylitol‐supplemented media. Acid production from glucose or fructose or uptake of xylitol was initiated by adding ¹⁴C‐labelled glucose, fructose or xylitol to bacterial suspensions. The resultant metabolites were identified by HPLC. Lactate was the major metabolite from glucose, whether the bacteria were grown in the presence or the absence of xylitol. Lactate production per colony‐forming unit was lower in X‐S cells than in X‐R cells. Fructose was metabolized by both X‐R and X‐S cells. Both X‐R and X‐S cells took up xylitol, but xylitol‐5‐P was detected in X‐S cells only. Total polysaccharides were measured through production of C¹⁴‐labelled ethanol‐insoluble polymers from [U¹⁴‐C]‐sucrose. No difference in polysaccharide production was found between X‐R and X‐S cells. The present study thus does not support the contention that X‐R are less cariogenic than X‐S mutans streptococci.     

糖尿病病人静脉药物治疗中溶液应用研究进展

介绍了葡萄糖的替代溶液在糖尿病病人静脉药物治疗中应用研究进展，替代溶液既能补充热量又不影响病人血糖波动，克服了静脉输注葡萄糖、生理盐水对病人的影响。     

口服木糖醇对糖尿病大鼠肾脏IGF-Ⅰ表达的影响

目的检测口服木糖醇对实验性1型糖尿病模型大鼠血糖及肾脏IGF-Ⅰ表达的影响。方法链脲佐菌素(STZ)一次性尾静脉注射造1型糖尿病大鼠模型,将成模大鼠随机分为糖尿病对照组(DC),糖尿病5%、10%、20%木糖醇(Xy)喂养组(D+5%、10%、20%Xy),另外设置正常对照组(NC)。喂养中分别在饲料中添加不同比例的木糖醇,开始分组喂养前留取血糖结果,第8 w末处死,处死前测量血糖。通过SABC免疫组织化学和定量分析方法观察各组大鼠肾脏IGF-Ⅰ表达的平均光密度(MOD)。结果血糖结果≥16.7 mmol/L证实模型构建成功。差异性喂养8 w后,各糖尿病组(DM)血糖与NC组相比仍升高(P<0.05),DC组血糖较0 w升高(P<0.05),而各D+Xy组8 w较0 w无明显变化。肾皮质/髓质IGF-Ⅰ表达的组间变化趋势一致:DC组较NC组IGF-Ⅰ表达量高;相比于DC组,随着饲料中添加木糖醇以及浓度的升高,IGF-Ⅰ表达量有逐渐降低趋势;皮质D+20%Xy组较DC组降低(P<0.01)且已与NC组无差异,髓质三个D+Xy组的IGF-Ⅰ表达量介于NC组、DC组之间。糖尿病大鼠在口服不同浓度木糖醇8 w后血糖与肾脏IGF-Ⅰ的表达量高度相关,r皮质=0.981(P=0.019),r髓质=0.998(P=0.002)。当血糖t∈28～35 mmol/L,皮质/髓质回归曲线方程可分别表示为y=186.036-705.932/t(R2=0.977,P=0.012),y=122.038+13.157 l nt(R2=0.997,P=0.002)。结论口服一定剂量木糖醇可稳定血糖及抑制肾脏IGF-Ⅰ表达,具有一定保护肾脏的作用。     

丹红注射液与木糖醇注射液配伍的稳定性研究

目的 考察丹红注射液与木糖醇注射液配伍的稳定性,为糖尿病患者的用药提供参考依据.方法 按照《中国药典》中的方法,模拟临床常用药物浓度,配制样品溶液,分别检测配伍液放置0、1、2、4、6h后的外观性状、pH值、不溶性微粒和含量变化.结果 丹红注射液与木糖酵注射液配伍后6h内,各项指标均无明显变化.结论 丹红注射液可与木糖醇注射液配伍,配伍液在6h内稳定.     

木糖醇改善^13C-尿素呼气试验患者的依从性研究

目的观察木糖醇对13C-尿素呼气试验检测试剂的口感及DOB检测值的影响。方法 120例病人同时进行不添加和添加木糖醇0.05g和0.10g组,自评检测的试剂口感,并配对检验两次检测的DOB值变化。结果木糖醇0.05g组和0.10g组,口感可接受百分比分别为43.3%和66.7%,显著高于未添加木糖醇时检测（分别为20.0%和33.3%,P〈0.05）,添加木糖醇0.10g口感可耐受百分比显著高于添加0.05g组（P〈0.05）。两种剂量木糖醇对DOB检测值均无显著性影响（P〉0.05）。结论在13C-尿素呼气试验检查试剂中加入适量木糖醇可改善口感、提高病人依从性、其中添加0.10g木糖醇效果最优,对13C-尿素呼气试验的DOB值无影响。