木瓜蛋白酶降解壳聚糖

通过粘度测定、还原端基测定和凝胶层析分子式量分布测定 ,研究了木瓜蛋白酶非专一性降解壳聚糖过程中温度、pH值、反应时间和酶用量等因素对木瓜蛋白酶降解能力的影响 ,探讨了壳聚糖脱乙酰化度和相对分子质量与木瓜蛋白酶降解反应的关系 .结果表明 :木瓜蛋白酶在温度4 0～ 4 5℃、pH 4 .0～ 5 .0和酶用量 0 .5 %～ 10 %范围内 ,对壳聚糖的降解将随酶用量的增加而加快 ,但随脱乙酰度的升高而减慢 ;木瓜蛋白酶适合作用于数均分子式量在 2 0～ 5万的虾壳聚糖 .     

微波对甲壳素脱乙酰反应的影响

在反应初期，壳聚糖的脱乙酰度随温度的升高而增大，而后反应速率减慢，脱乙酰度的变化也减小。当NaOH溶液质量分数达到45％左右、温度达100℃以上后，反应速率急剧提高，脱乙酰度也发生较大变化。对于NaOH溶液的加热，与常规加热方式相比，微波具有快速加热的优越特性。利用H－NMR研究发现，微波对甲壳素脱乙酰反应有一定的“非热效应”。     

国内壳聚糖导管用于神经再生的研究现状

壳聚糖，又称脱乙酰几丁质、聚氨基葡萄糖、可溶性甲壳素，是由甲壳素经脱乙酰化反应转化变成的生物大分子，分子量为12-59万。化学名2-氨基-B-1，4-葡聚糖，分子式为：（C6H11O4N）n。壳聚糖在自然界中广泛分布于某些藻类和虾、蟹、昆虫等的骨骼及外壳中，易于获得。壳聚糖在人体内可以被降解为氨基葡萄糖，体内不积蓄，可被人体吸收，无免疫原性，具有很好的生物相容性和生物可降解性及一定的抗菌和抗肿瘤等特性，因此被广泛地应用于生物医学工程领域。     

双突跃电位滴定法测定壳聚糖脱乙酰度的影响因素

研究了双突跃电位滴定法测定壳聚糖脱乙酰度的准确性以及壳聚糖溶液质量浓度、粘度、不同脱乙酰度等因素对滴定终点测定结果的影响.结果表明:壳聚糖样品质量浓度控制在2～6g/L,利用双突跃电位滴定法可以测定壳聚糖的脱乙酰度,不同样品脱乙酰度测定结果RSD(相对标准偏差)小于0.61%(n=3),该方法具有较高地准确性,可以用于壳聚糖生产和加工过程中的质量控制与检测.     

羧甲基壳聚糖结构与性质研究

由X-射线衍射证明壳聚糖在进行化学改性(羧甲基化)后,晶体结构已破坏,呈无定形结构,因而在任何pH范围内均溶于水。用元素分析法与红外光谱法测定羧甲基壳聚糖的取代度DS>1和脱乙酰化度为84%～92%,由此推断在C_2和C_6位上均有羧甲基取代,化学改性后的壳聚糖为N,O取代(即为N,O-CMC)。由凝胶过滤色谱测得N,O-CMC的分子量约为10~5～10~6,1%(W/V)的N,O-CMC溶液在50s~(-1)时的表观粘度为20mPa·s左右。     

壳聚糖的溶解性能及体内生物相容性评价

目的：观察酸溶性壳聚糖在醋酸溶液中的溶解相关性指标,并对水溶性及酸溶性两种壳聚糖的体内相容性和降解性进行评价,为壳聚糖组织工程支架的制备和应用提供参考。方法：用1%的醋酸溶液配制质量浓度为1%、2%、3%、4%的酸溶性壳聚糖溶液,利用黏度分析仪器和pH计测定其黏度和pH值;将2%的酸溶性壳聚糖溶液溶解在不同体积分数（1%、1.5%、2%、2.5%、3%）的醋酸溶液中,检测其黏度和pH值的变化。在BALB/c小鼠腿部肌肉内植入酸溶性壳聚糖或水溶性壳聚糖0.1 g,比较组织相容性和体内降解时间。结果：酸溶性壳聚糖溶液的黏度、pH值随壳聚糖质量浓度的增加而增加。等量的壳聚糖溶解在不同酸度的醋酸中,其黏度和pH值均随酸度的增加而降低。水溶性壳聚糖生物相容性要优于酸溶性壳聚糖,水溶性壳聚糖降解时间〈7 d,酸溶性壳聚糖降解时间〉21 d。结论：壳聚糖在醋酸溶液中的溶解性能与溶液的酸度有关,溶液的黏度和pH值与壳聚糖质量浓度和酸浓度两个因素均密切相关。水溶性壳聚糖的体内相容性及降解性明显优于酸溶性壳聚糖。     

交联温度对京尼平交联胶原／壳聚糖组织工程支架的影响

[目的]通过研究材料的孔径、交联度、溶胀率、降解率、细胞毒性及组织相容性的变化,探讨交联温度对京尼平交联胶原/壳聚糖支架的影响.[方法]采用冷冻干燥法制备胶原/壳聚糖复合多孔支架,分别于4℃、20℃、36℃条件下,在0.5%京尼平水溶液中交联24 h.以未交联的胶原/壳聚糖复合多孔支架作为对照,评价所得支架的孔径、交联度、溶胀率、降解率、细胞毒性及组织相容性特点.[结果]随交联温度升高,支架的交联度明显增大,溶胀率和降解率逐渐减小.4℃组支架交联度47.88%土6.4%,溶胀率为721%±46%,4周后降解3.95%±6.4%;20℃组支架交联度67.69%±3.6%,溶胀率为662%±72%,4周降解0.91%±5.9%;36℃组支架交联度70.32%±5.7%,溶胀率为635%±27%,4周降解0.66%±7.3%,三组上述观察指标均优于未交联组(P/0.01).[结论]京尼平交联可以显著降低胶原/壳聚糖支架的降解率和溶胀率,且对支架结构和生物相容性无明显影响.交联温度增加可以提高支架的交联度和抗降解能力,较快获得具有良好生物相容性和降解率的组织工程支架.     

离子交换层析色谱法分离壳聚糖

用CMsepharoseCL 6B离子交换剂,使用不同的柱尺寸,采用离子强度线性梯度洗脱,对脱乙酰度80%,90%的壳聚糖样品进行分离。从脱乙酰度80%的壳聚糖样品分离得到3个组分实验结果表明,采用线性梯度洗脱时,直径相同的柱子,长的离子交换柱有利于壳聚糖的分离;对同一根离子交换柱,线性梯度洗脱体积的增加有利于壳聚糖的分离.分离不同脱乙酰度壳聚糖时,高脱乙酰度壳聚糖较低脱乙酰度壳聚糖在起始缓冲液洗脱时,洗脱出的壳聚糖含量较低,在高离子强度处洗脱出的壳聚糖含量较高.     

用于软骨缺损修复的壳聚糖水凝胶降解性能的表征

背景:壳聚糖水凝胶修复软骨缺损生物相容性好,但目前尚不明确壳聚糖水凝胶在软骨缺损修复过程中的降解性能变化。目的:探讨壳聚糖水凝胶在软骨缺损修复过程中的降解性能变化。方法:采用羟乙基脱乙酰壳多糖(glycolchitosan,GC)与二醛基聚乙二醇(OHC-PEG-CHO)通过席夫碱反应交联,形成可注射水凝胶。考察不同浓度的水凝胶(GC/OHC-PEG-CHO:2 wt%/2 wt%和2 wt%/1 wt%)在体外降解中的pH值、质量和体积变化。结果:水凝胶在降解过程中,pH值基本维持在7左右;水凝胶(GC/OHC-PEG-CHO:2 wt%/1 wt%)在6周时全部降解,而水凝胶(GC/OHC-PEG-CHO:2 wt%/2 wt%)在8周时质量为初始质量的44.30%±5.51%,体积为初始体积的50.64%±9.81%,该降解速度与软骨修复速率一致。选取水凝胶(GC/OHC-PEG-CHO:2 wt%/2 wt%)植入新西兰大白兔皮下,组织学切片分析结果表明,3周时水凝胶明显变小,但无明显的炎症反应。结论:初步降解实验表明GC/OHC-PEG-CHO水凝胶可用于软骨缺损修复。     

不同材料人工真皮支架修复猪Ⅲ度烧伤创面比较

目的 比较胶原壳聚糖真皮支架、胶原磺化羧甲基壳聚糖真皮支架及脱细胞基质真皮支架移植于Ⅲ度烧伤创面后,真皮支架的血管化及支架上表皮移植修复创面情况.方法 将3种不同真皮支架各移植于6头猪(共18头猪)Ⅲ度烧伤清创后创面,在植入后1、2、3周对真皮支架血管化、创面、支架上表皮移植愈合和修复情况进行观察,同时用免疫组织化学方法,对CD34阳性信号(新生血管数目)进行检测.以无支架植入的Ⅲ度烧伤清创后创面为对照.结果 胶原磺化羧甲基壳聚糖真皮支架植入后2周支架血管化已基本完成,而胶原壳聚糖和脱细胞基质真皮支架至少需要3周.3种不同材料支架垂直于创面的新生微血管均比无支架对照创面多;不同材料支架组与对照组2周创面比1周创面、3周创面比2周创面CD34的表达均明显增多,胶原磺化羧甲基壳聚糖真皮支架组植入后1、2、3周CD34阳性信号均明显高于相对应的其他3组;胶原磺化羧甲基壳聚糖真皮支架植入后1周,创面植表皮,移植表皮存活良好,而胶原壳聚糖和脱细胞基质真皮支架植入需要2周,其表面移植的表皮细胞才能成活.结论 3种材料的支架均可修复Ⅲ度烧伤创面,而以胶原磺化羧甲基壳聚糖真皮支架的血管化程度最好.     

Alkali citrate for preventing recurrence of calcium oxalate stones

The use of alkali citrates for preventing the recurrence of calcium oxalate stones was investigated in two trials. In trial I, alkali citrates were given continuously for 18 months to 8 patients who had shown a tendency to recurrent stone formation. In trial II, 12 similar patients were given intermittent therapy for 12 months. The expected changes in urine chemistry were checked at intervals of 3 months. Recurrent stone formation (2 episodes) was observed in only 1 patient (in trial II) during alkali citrate administration; before therapy this patient had suffered an average of 10 attacks of stone formation annually. In the light of the experience gained in these trials, continuous administration of alkali citrates is recommended; the duration of treatment should be tailored to individual needs, but it should not be prolonged indefinitely. Besides having well-attested effectivity of stone prevention, this mode of therapy carries a relatively low incidence of side effects.     

A case of the milk-alkali syndrome with a small amount of milk and magnesium oxide ingestion--the contribution of sustained metabolic alkalosis induced by hypertonic dehydration

We described a patient with the milk-alkali syndrome induced by the ingestion of small amount of milk (200 ml/day) and ice cream (145 g/day) and the administration of small dose of absorbable alkali (magnesium oxide 2.0 g/day) for the treatment of chronic constipation. The present case shows not only triads, i.e., hypercalcemia (s-Ca 14.3 mg/dl), metabolic alkalosis (s-HCO3- 37.4 mEq/L), and renal insufficiency (s-Cre 2.3 mg/dl) but also hypernatremia (s-Na 161 mEq/L) and hypertonic dehydration after the frequent episodes of elevated body temperature. The milk-alkali syndrome has been defined as the hypercalcemia with a metabolic alkalosis from a high amount of calcium intake and long term administration of absorbable alkali in any form, usually as calcium carbonate for the treatment of peptic ulcer. As the present case could be distinguished from any other cases previously reported with regard to the amount of calcium (0.4 g/day) and alkali (36 mEq/day) intake and the clinical situations that induced the syndrome, we compared the present case with the previous reports, calculating the amount of calcium and alkali intake from milk and absorbable alkali. After the introduction of the H2 blockers for peptic ulceration, the most cases with milk-alkali syndrome had provoked by the smaller amount of calcium than previously reported, which were associated with the treatment of relatively large amount of alkali (50-150 mEq/day), suggesting the role of sustained metabolic alkalosis for the development. In the present case the metabolic alkalosis induced by hypertonic dehydration and enhanced by absorbable alkali intake also could cause an increase of renal tubular reabsorption of calcium and a decrease of ionized calcium which might produce increased secretion of parathyroid hormone followed by vitamin D3 activation and increased Ca absorption from the gut. The metabolic alkalosis might be essential to the development of the milk-alkali syndrome without a high calcium and absorbable alkali intake.     

Evaluation of the effects of resveratrol and bevacizumab on experimental corneal alkali burn

Purpose

To evaluate the effects of resveratrol and bevacizumab on experimental corneal neovascularization.

Method

A corneal alkali burn was performed in 62 eyes of 31 male white Vienna rabbits. Resveratrol (group 1), dimethyl sulfoxide (group 2), bevacizumab (group 3) and 0.9% NaCl (group 4) were administered to both eyes of the rabbits by subconjunctival injection for 7 days. Corneal photos were taken at 15 days after alkali injury. Inflammatory index scores and neovascularization areas were calculated.

Results

In bevacizumab group both inflammatory index scores and the calculation of the corneal neovascularization area was significantly less than the groups.

Conclusion

The subconjunctival administration of bevacizumab inhibits corneal neovascularization effectively in the rabbit corneal alkali burn model. No effect of resveratrol to the corneal neovascularization on experimental model of the corneal alkali burn was seen at the doses of usage.     

Transient neonatal distal renal tubular acidosis with secondary hyperparathyroidism

We describe a neonate with distal renal tubular acidosis with secondary hyperparathyroidism manifesting as hyperchloraemia, hypercalcaemia, elevated serum parathyroid hormone (PTH) and life-threatening metabolic acidosis. He exhibited general weakness, tachypnoea, dry skin and weight loss. Urinary excretion of titratable acid and ammonium was decreased. Daily alkali (2.5 mEq/kg body weight) was required to maintain a normal plasma bicarbonate (HCO₃–). With alkali therapy, the fractional excretion of HCO₃– was below 5%. Serum calcium and PTH were restored to normal promptly on initiation of alkali therapy. After 5 months of alkali therapy, normal growth and urine acidifying ability were restored and alkali therapy was discontinued. The acidification defect in this patient was transient. We consider this patient to be consistent with Lightwood's syndrome of transient infantile renal tubular acidosis.     

An experimental study on the effect of vagotomy on stress ulcer and the influence of bile reflux

I investigated the significance of bile reflux, when vagotomy was done to stress ulcer, by means of measuring gastric ulcer index, gastric pH and serum gastrin levels of rats. And in order to examine influence of alkali factor of bile, I measured gastric acid output and serum gastrin levels after alkali or acid solution was infused into the untreated rat's stomach. Results were summarized as follows: 1. When I infused alkali solution into the untreated stomach, there was no significant change in serum gastrin level but gastric acid output was significantly accelerated, as compared with infusing acid solution. On the other hand, when I infused alkali solution into the vagotomized stomach, serum gastrin level increased significantly and gastric acid output was significantly accelerated, as compared with infusing acid solution, so, acceleration of acid output observed when I infused alkali solution into the untreated stomach was not suppressed in spite of vagotomy operation. 2. In the vagotomized group, gastric acid output was significantly suppressed and serum gastrin level increased significantly as compared with the untreated group. But, when bile was led into the stomach in the vagotomized group, acid output was accelerated and serum gastrin level also showed a tendency to increase as compared with the group of vagotomy alone. 3. When mild stress was inflicted, stress ulcer formation was significantly prevented in the bile reflux group (vagotomy + pyloroplasty) as well as in the non-bile reflux group (vagotomy + pyloric ligation + gastroileostomy) if vagotomy was done. But, when severe stress was inflicted, stress ulcer formation was significantly prevented in the non-bile reflux group, but not prevented in the bile reflux group. As mentioned above, it was proved that stress ulcer formation was not prevented under a severe stress, if bile reflux existed, even though vagotomy was done. So, if we do vagotomy operation, we need to choose the operation method not to induce bile reflux as much as possible.     

Animal study on expression of laminin and fibronectin in cornea during wound healing following alkali burn

Objective:To observe the expression of laminin and fibronectin in alkali-burned corneas in rats.Methods:A total of 18 normal Wistar rats were randomly divided into 6 groups(n=3 in each group).For each rat, one eye was injured by alkali burn,the other one was taken as the normal control.Then all the corneas were surgically removed and the expression of laminin and fibronectin was observed with immunohistochemistry respectively at 7 hours,1 day,3 days, 7 days,14 days and 28 days after alkali burn.Results:Compared with that of the normal controls, the expression of laminin and fibronectin of the burned eyes was dramatically higher at 7 hours, reached peak at 14 days and decreased to the normal level at 28 days after alkali burn.Conclusions:In the process of wound healing after alkali burn, the expression of laminin and fibronectin increases dramatically, which suggests that laminin and fibronectin may participate in the process of corneal wound healing.     

The in-vivo effect of sodium-potassium citrate on the crystal growth rate of calcium oxalate and other parameters in human urine

Summary In this study, an efficient microtechnique (gel crystallization method) was used to investigate the in-vivo effect of sodium-potassium citrate on the crystal growth rate of calcium oxalate (Vcr) in human urine samples of 6 healthy volunteers. With a daily dose of 3x11 mmol of alkali citrate, Vcr decreased by 70%. This could have been due to the decrease of calcium excretion, which caused 50–60% of the total change, and to the increase of citrate and pH, each contributing about 20–25% to the decline of Vcr. The findings explain the clinical advantages of alkali citrates in the prevention of recurrent calcium oxalate stone formation.     

Corrosive burns of the esophagus and stomach: a recommendation for an aggressive surgical approach

During a six-year period ending in December, 1980, 62 patients with a history or clinical evidence of corrosive ingestion were admitted into our institutions. The majority were adults who had attempted suicide. Strong alkali (lye), the most common corrosive agent involved, was ingested by more than half of the patients (39). The remaining 23 patients had ingested weak alkali or nonalkali corrosive agents. Of the 27 patients with severe esophagogastric burns (second- and third-degree), a 43.5% incidence overall, liquid lye was responsible in 21, including 7 of 8 patients with extensive full-thickness esophagogastric necrosis. In sharp contrast, only 1 of the 23 patients who had ingested weak alkali or nonalkali corrosive agents had serious esophagogastric injury. In the first two years of this review, the management approach was the so-called standard one (esophagoscopy, steroids, antibiotics, and dilation) (Group 1). The results were disappointing. In 5 of 9 patients with endoscopic findings of second-degree burns, stricture requiring dilation developed, and all 4 with extensive full-thickness esophagogastric necrosis died. In contrast, during the last four years, with the adoption of a more aggressive surgical approach, that is, early surgical intervention including the use of an intraluminal esophageal stent and radical resection as indicated, missed or delayed diagnosis of full-thickness esophagogastric necrosis with its prohibitive mortality was avoided and the complication of severe esophageal stricture was virtually eliminated (Group 2).(ABSTRACT TRUNCATED AT 250 WORDS)     

法夫酵母中虾青素的稳定性研究

采用贮藏试验对碱法破壁酵母类胡萝卜素的稳定性进行了研究。结果表明，不同贮藏条件下，酵母色素连续以两个速度常数不同的一级方程进行降解（k1〉k2）。第一个一级反应主要反映受损脂肪粒中类胡萝卜紊的变化，第二个反应主要反映未受损脂肪粒中类胡萝卜素的变化。比较不同贮藏条件下的试验结果及各个动力学方程的速度常数，表明采用低温、避光、隔氧及添加抗氧化剂有利于提高酵母色素的存留率，而酵母水分（〈12％）及矿物盐对之影响不大。     

Reversible low-molecular-weight proteinuria in patients with distal renal tubular acidosis

Four patients with untreated renal tubular acidosis had a urinary excretion of low-molecular-weight (LMW) proteins which was restored to normal by alkali therapy. Hypokalaemic proximal tubular damage in untreated patients with distal renal tubular acidosis is believed to be the cause of LMW proteinuria. An examination of urinary excretion of LMW proteins is useful for determining hypokalaemic proximal tubular dysfunction, as well as the efficiency of alkali therapy.