壳聚糖固定谷氨酸脱羧酶的研究

以壳聚糖为载体，戊二醛为交联剂。制备固定化谷氨酸脱羧酶(GDC)，研究固定化反应中pH值、戊二醛浓度、给酶量以及交联反应搅拌时间对固定化GDC活力的影响以及GDC固定化酶和自由酶的酶学特性。实验结果表明：壳聚糖固定化GDC的最适pH4．4．最适温度55℃。与自由酶相比。具有较好的热稳定性、贮存稳定性及可操作性；在米胚芽生产制备γ-氮基丁酸中具有实用价值。     

用CHITOSAN固定化青霉素酰化酶

本文报道以Chitosan为载体制备固定化青霉素酰化酶的研究结果。1.4％ Chitosan醋酸溶液先用12.5％戊二醛交联,洗涤,研磨,得颗粒。再用1.5％pH5.5和1.5％pH8.5多聚磷酸处理,得机械强度良好的载体。此载体先后经0.5％戊二醛和对甲苯磺酰氯双活化后,再与青霉素酰化酶偶联。所得固定化酶的活力达20.8u/g。固定化青霉素酰化酶的反应最适温度略高于游离酶,最适pH略低于游离酶;其Km值基本接近游离酶。固定化酶经反复使用,活力基本不变。     

AS1.398中性蛋白酶固定化条件的初步研究

考察壳聚糖、卡拉胶、海藻酸钠、琼脂等化载体对ＡＳ１．３９８中性蛋白酶固定化的 影响，确定０．３％戊二醛在３０℃、ＰＨ８．０的条件下处理壳聚糖８－１０ｈ，加酶液，固定８ｈ，酶活力回收约为７７％，固定化酶最适作用温度为５５℃，最适作用ＰＨ为８．０；固定化酶的稳定性比游离酶的稳定性有显著提高。     

壳聚糖珠固定化乳糖酶的条件及特性研究

目的研究乳糖酶的固定化。方法以壳聚糖珠(2.0 g)为载体,0.02%戊二醛为交联剂,考察固定化乳糖酶的条件及其特性。结果固定化条件:室温状态下,在pH 6.0、酶量0.2 mg/mL的酶液中固定12 h,固定化乳糖酶活力回收率为31.5%。乳糖酶、固定化乳糖酶的最适pH值分别为5.0~5.5,5.5~6.5;最适温度分别为40℃,50℃。结论固定化乳糖酶最适温度和pH值比溶乳糖高。     

壳聚糖固定化酵母蔗糖酶的研究

用壳聚糖作吸附剂、戊二醛作交联剂,对酵母蔗糖酶进行固定化研究,同时用琼脂糖固定化的蔗糖酶和游离酶与其进行比较。结果表明,壳聚糖固定化蔗糖酶贮藏稳定性、对变性剂以及对温度的耐受性均明显优越,而Km值与琼脂糖固定化酶相当,但比游离酶明显增高,酶的最适pH三者相近。研究表明,壳聚糖固定化酶所需的戊二醛浓度为0.6%,交联时间不低于6 h。固定化蔗糖酶对变性剂(乙醇、脲)的耐受力明显高于游离酶。     

固定化超氧化物歧化酶的制备

目的 研究固定化超氧化物歧化酶(SOD)的制备方法。方法 分别以不同方法对铜锌超氧化物歧化酶(CuZnSOD)进行固定并比较其活力,对固定化方法进行相应的考察和优化。结果 以壳聚糖为载体,戊二醛交联法制备固定化SOD酶,酶活力和酶活回收率均较理想,固定化过程中的pH在6.0-8.2范围内,对固定化效果无明显影响;优化条件下制备的固定化铜锌超氧化物歧化酶,所得壳聚糖酶粉活力可达141 U·g-1,酶活回收率大于60％。结论 壳聚糖-戊二醛交联法可用于固定化超氧化物歧化酶粉的制备。     

交联壳聚糖微球偶联胰蛋白酶研究

采用反相悬浮交联法,制备交联壳聚糖微球(CCTS),再以戊二醛为偶联剂,偶联胰蛋白酶.研究了胰蛋白酶偶联的最佳条件和偶联后酶的理化性质.结果表明:用终浓度为0.6%的戊二醛,在50℃下,先处理CCTS 6 h,再置冰浴加酶为12 mg/g,搅拌24 h,固定化酶活性回收率达63.4%.胰蛋白酶与壳聚糖微球偶联的最适温度为80℃、最适pH值为7、表观米氏常数(Km)为3.16 mmol/L.与壳聚糖载体相比,CCTS具有机械强度好、粒度均匀、耐酸性能好、对牛血清白蛋白非特异性吸附较弱的优点.     

固定化β-葡萄糖苷酶制备人参皂苷F_1的研究

本文探讨了β-葡萄糖苷酶的固定化方法,及利用固定化β-葡萄糖苷酶转化人参皂苷Rg1为人参皂苷F1的转化工艺。确定交联-包埋法为最佳固定化方法,应用正交实验得出最佳制备条件为:交联时间3h,戊二醛浓度0.1%,海藻酸钠浓度1%,CaCl2浓度2%。固定化酶与游离酶在热稳定性和pH值稳定性方面显示出不同的性质,其中固定化β-葡萄糖苷酶的最适反应温度为70℃,最适反应pH值为5.5。固定化β-葡萄糖苷酶在15℃环境中保存30d后,酶活回收率为68.82%。固定化β-葡萄糖苷酶转化人参皂苷Rg1为人参皂苷F1的转化条件为:固定化酶承载量为3.76U/g固定化酶载体,底物浓度为0.2mg/mL,转化温度为40℃,转化周期为2d,转化次数为4次,平均转化率为80.49%。     

固定化α-淀粉酶的研究

以壳聚糖为载体,戊二醛为交联剂,将α-淀粉酶固定。结果表明固定化酶与原酶均有两个最适pH值(5.0,6.5);固定化酶在70℃仍有较高热稳定性,而原酶活力明显下降;固定化酶的K’m=0.62×10-2m g.mL-1,原酶Km=1.12×10-2m g.mL-1。     

壳聚糖微球固定化重组TEM-116型ESBL的研究

目的 利用固定化酶技术,使重组TEM-116型超广谱β-内酰胺酶(ESBL)在清除环境中残留抗生素的应用中可重复使用,并改善其稳定性.方法 以戊二醛为交联剂将重组TEM-116型ESBL固定于壳聚糖微球载体,并采用单因素轮换法和响应曲面法对固定化条件进行优化.结果 4℃条件下,当戊二醛浓度0.54%、交联pH5.4、给酶量0.58IU/g壳聚糖微球、固定化pH6.2时,同定化酶的酶活和回收率分别可达到0.49IU/g和84%(0.49IU/0.58IU).与游离酶相比,固定化酶的酸碱稳定性和可重复利用性得到显著提高,在pH5.8～7.4范围内酶活性保持在73%～100%的水平,经7次重复性使用,每次1h,酶活力保留高达80%.结论 通过固定化酶技术,以重组TEM-116型ESBL为代表的耐药酶能够开发为具有广泛应用前景的环保制剂,以消除外环境中残留的抗生素.     

Efficacy of gut lavage,hemodialysis, and hemoperfusion in the therapy of paraquat or diquat intoxication

Clinical and in vitro investigations were carried out to test the efficacy of gut lavage, hemodialysis, and hemoperfusion in the treatment of poisoning with paraquat or diquat. In a patient suffering from diquat intoxication 130 times more diquat was removed by gut lavage 30 h after ingestion than was removed by complete aspiration of the gastric contents.Determination of in vitro clearances for paraquat and diquat by hemodialysis showed that, at serum concentrations of 1–2 ppm, such as are frequently encountered in poisoning in man, toxicologically relevant quantities of herbicide cannot be removed from the body. At a concentration of 20 ppm, on the other hand, hemodialysis proved to be effective, the clearance being 70 ml/min at a blood flow rate of 100 ml/min. The efficacy of hemoperfusion with coated activated charcoal was on the whole better. Especially at concentrations around 1–2 ppm, the clearance values for hemoperfusion were some 5–7 times higher than those for hemodialysis.In a patient suffering from paraquat poisoning, both hemodialysis as well as hemoperfusion were carried out. The in vitro results could be confirmed: At serum concentrations of paraquat less than 1 ppm no clearance could be obtained by hemodialysis while by hemoperfusion with activated charcoal quite high clearance values were measured and the serum level dropped down to zero.

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Zusammenfassung Klinische Untersuchungen und Laboratoriumsversuche wurden durchgeführt, um die Wirksamkeit von Darmspülung, Hämodialyse und Hämoperfusion bei Paraquat- und Deiquat-Vergiftungen zu prüfen.Bei einem Patienten wurde 30 Std nach Deiquat-Aufnahme durch Darmspülung 130mal mehr Deiquat entfernt als durch vollständige Aspiration des Mageninhaltes. In vitro-Versuche ergaben, daß bei Blutserumkonzentrationen von 1–2 ppm, die bei Vergiftungen oft gemessen werden, durch Hämodialyse keine toxikologisch relevanten Paraquat- oder Deiquat-Mengen entfernt werden können. Dagegen erwies sich die Hämodialyse bei 20 ppm und einer Blutumlaufgeschwindigkeit von 100 ml/min mit einer Clearance von 70 ml/min als wirksam. Die Hämoperfusion mit beschicheter Aktivkohle war in diesen Versuchen aber eindeutig überlegen, denn insbesondere bei Konzentrationen um 1–2 ppm waren die Clearance-Werte 5–7mal höher als bei der Hämodialyse.Die in vitro-Ergebnisse wurden bei einem Patienten mit einer Paraquat-Vergiftung bestätigt: Bei Konzentrationen unter 1 ppm war die Hämodialyse wirkungslos, während durch Hämoperfusion relativ hohe Clearance-Werte erreicht wurden, so daß der Serumspiegel rasch unter die Nachweisgrenze abfiel.

     

Aquatic Insects and Trace Metals: Bioavailability,Bioaccumulation, and Toxicity

Abstract

The uptake of metals from food and water sources by insects is thought to be additive. For a given metal, the proportions taken up from water and food will depend both on the bioavailable concentration of the metal associated with each source and the mechanism and rate by which the metal enters the insect. Attempts to correlate insect trace metal concentrations with the trophic level of insects should be made with a knowledge of the feeding relationships of the individual taxa concerned. Pathways for the uptake of essential metals, such as copper and zinc, exist at the cellular level, and other nonessential metals, such as cadmium, also appear to enter via these routes. Within cells, trace metals can be bound to proteins or stored in granules. The internal distribution of metals among body tissues is very heterogeneous, and distribution patterns tend to be both metal and taxon specific. Trace metals associated with insects can be both bound on the surface of their chitinous exoskeleton and incorporated into body tissues. The quantities of trace meals accumulated by an individual reflect the net balance between the rate of metal influx from both dissolved and particulate sources and the rate of metal efflux from the organism. The toxicity of metals has been demonstrated at all levels of biological organization: cell, tissue, individual, population, and community. Much of the literature pertaining to the toxic effects of metals on aquatic insects is based on laboratory observations and, as such, it is difficult to extrapolate the data to insects in nature. The few experimental studies in nature suggest that trace metal contaminants can affect both the distribution and the abundance of aquatic insects. Insects have a largely unexploited potential as biomonitors of metal contamination in nature. A better understanding of the physico-chemical and biological mechanisms mediating trace metal bioavailability and exchange will facilitate the development of general predictive models relating trace metal concentrations in insects to those in their environment. Such models will facilitate the use of insects as contaminant biomonitors.     

Alzheimer’s disease – current trends in basic and clinical research. Highlights from the 16th ECNP

Advances in the molecular biological knowledge of neuronal nicotinic acetylcholine receptors (nAChRs) have led to a growing interest by the pharmaceutical industry in the development of novel compounds that selectively modulate nAChR function. The ability of (-)-nicotine, an activator of nAChRs, to enhance attentional aspects of cognition in animals and humans, to exert neuroprotective and anxiolytic-like effects, and presumably to mediate the negative correlation between smoking and Alzheimer's (and Parkinson's) Disease, has focused interest on the potential therapeutic utility of modulators of nAChR function for treatment of some of the deficits associated with these progressive, neurodegenerative conditions. Numerous compounds are known which activate nAChRs and which might serve as lead compounds toward the development of such agents. The pharmacologic diversity of neuronal nAChR subtypes suggests the possibility of developing selective compounds which would have more favourable side-effect profiles than existing agents. This broader class of agents, collectively called cholinergic channel modulators (ChCMs), is anticipated to encompass compounds which would have more favourable side-effect profiles than existing agents, which generally exhibit low selectivity. This selectivity may be achieved by preferentially activating some subtypes of nAChRs (i.e., Cholinergic Channel Activators, ChCAs) or inhibiting the function of other subtypes (Cholinergic Channel Inhibitors, ChCIs). An overview of the biology of nAChRs and the rationale for the use of ChCMs for the treatment of dementia related to neurodegenerative diseases are presented, followed by a discussion of lead compounds and compounds under consideration for clinical evaluation.     

2-(Acetoxyphenyl)-(Z)-styryl sulfides as cyclooxygenase inhibitors

2-(Acetoxyphenyl)-(Z)-styryl sulfides are described as selective cyclooxygenase-2 (COX-2) inhibitors, useful for treating inflammation and COX-2-mediated disorders including neoplasia. 2-(Acetoxyphenyl)-(Z)-styryl sulfide is claimed to be the most potent COX inhibitor in the series with a COX-2 selectivity ratio of 33. This compound is also claimed to be superior to celecoxib (Celebrex^®, Pfizer) in inhibiting cell growth of colorectal carcinoma cells. In this evaluation, the COX inhibitory activity of this compound is compared to that previously disclosed for diarylheterocycles and 2-(acetoxyphenyl)alkyl sulfides. The validity of the DLD-1 cell line in the growth inhibition studies is questioned based on recent literature reports indicating the lack of COX-2 expression in this cell line.     

Sleep-disordered breathing with chronic opioid use

Chronic opioid use for pain relief or as substitution therapy for illicit drug abuse is prevalent in our societies. In the US, retail distribution of methadone and oxycodone has increased by 824 and 660%, respectively, between 1997 and 2003. μ-Opioids depress respiration and deaths related to illicit and non illicit chronic opioid use are not uncommon. Since 2001 there has been an emerging literature that suggests that chronic opioid use is related to central sleep apnoea of both periodic and non-periodic breathing types, and occurs in ～ 30% of these subjects. The clinical significance of these sleep-related abnormalities are unknown. This review addresses the present knowledge of control of ventilation mechanisms during wakefulness and sleep, the effects of opioids on ventilatory control mechanisms, the sleep-disordered breathing found with chronic opioid use and a discussion regarding the future research directions in this area.     

Drug targets for cognitive enhancement in neuropsychiatric disorders

The investigation of novel drug targets for treating cognitive impairments associated with neurological and psychiatric disorders remains a primary focus of study in central nervous system (CNS) research. Many promising new therapies are progressing through preclinical and clinical development, and offer the potential of improved treatment options for neurodegenerative diseases such as Alzheimer's disease (AD) as well as other disorders that have not been particularly well treated to date like the cognitive impairments associated with schizophrenia (CIAS). Among targets under investigation, cholinergic receptors have received much attention with several nicotinic agonists (α7 and α4β2) actively in clinical trials for the treatment of AD, CIAS and attention deficit hyperactivity disorder (ADHD). Both glutamatergic and serotonergic (5-HT) agonists and antagonists have profound effects on neurotransmission and improve cognitive function in preclinical experiments with animals; some of these compounds are now in proof-of-concept studies in humans. Several histamine H3 receptor antagonists are in clinical development not only for cognitive enhancement, but also for the treatment of narcolepsy and cognitive deficits due to sleep deprivation because of their expression in brain sleep centers. Compounds that dampen inhibitory tone (e.g., GABA_A α5 inverse agonists) or elevate excitatory tone (e.g., glycine transporter inhibitors) offer novel approaches for treating diseases such as schizophrenia, AD and Down syndrome. In addition to cell surface receptors, intracellular drug targets such as the phosphodiesterases (PDEs) are known to impact signaling pathways that affect long-term memory formation and working memory. Overall, there is a genuine need to treat cognitive deficits associated with many neuropsychiatric conditions as well as an increasingly aging population.