Neurodegeneration by activated microglia across a nanofiltration membrane

Microglia have been implicated in the pathogenesis of several neurodegenerative diseases, but their precise role remains elusive. Although neuron loss in the presence of lipopolysaccharide-stimulated microglia has been well documented, a novel coculture paradigm was developed as a new approach to assess the diffusible, soluble mediators of neurodegeneration. Isolated microglia were plated on membrane inserts that were coated with a layer of cellulose acetate. The cellulose acetate-coated membranes have nanofiltration properties, in that only molecules with masses less than 350 Da can pass through. Products released from activated microglia that were separated from primary ventral mesencephalon cells beneath the nanofiltering membrane were able to kill the dopamine neurons. Microglial cytokines cannot diffuse through this separating membrane. Addition of a nitric oxide synthase inhibitor prevented the loss of the dopamine neurons. These data describe a novel coculture system for studying diffusible factors and further support nitric oxide production as an important mediator in microglia-induced neuron death.     

Exogenous nitric oxide enhances cadmium tolerance of rice by increasing pectin and hemicellulose contents in root cell wall

To study the mechanisms of exogenous NO contribution to alleviate the cadmium (Cd) toxicity in rice (Oryza sativa), rice plantlets subjected to 0.2-mM CdCl₂ exposure were treated with different concentrations of sodium nitroprusside (SNP, a NO donor), and Cd toxicity was evaluated by the decreases in plant length, biomass production and chlorophyll content. The results indicated that 0.1 mM SNP alleviated Cd toxicity most obviously. Atomic absorption spectrometry and fluorescence localization showed that treatment with 0.1 mM SNP decreased Cd accumulation in both cell walls and soluble fraction of leaves, although treatment with 0.1 mM SNP increased Cd accumulation in the cell wall of rice roots obviously. Treatment with 0.1 mM SNP in nutrient solution had little effect on the transpiration rate of rice leaves, but this treatment increased pectin and hemicellulose content and decreased cellulose content significantly in the cell walls of rice roots. Based on these results, we conclude that decreased distribution of Cd in the soluble fraction of leaves and roots and increased distribution of Cd in the cell walls of roots are responsible for the NO-induced increase of Cd tolerance in rice. It seems that exogenous NO enhances Cd tolerance of rice by increasing pectin and hemicellulose content in the cell wall of roots, increasing Cd accumulation in root cell wall and decreasing Cd accumulation in soluble fraction of leaves.     

Effects of glucanase treatment on the structure and mechanical properties of cell walls in the giant‐celled xanthophycean alga Vaucheria frigida

The cell wall of the tip‐growing cells of the giant‐cellular xanthophycean alga Vaucheria frigida is mainly composed of cellulose microfibrils (CMFs) arranged in random directions and the major matrix component into which the CMFs are embedded throughout the cell. The mechanical properties of a cell‐wall fragment isolated from the tip‐growing region, which was inflated by artificially applied pressure, were measured after enzymatic removal of the matrix component by using a protease; the results showed that the matrix component is involved in the maintenance of cell wall strength. Since glucose and uronic acid are present in the matrix component of Vaucheria cell walls, we measured the mechanical properties of the cell wall after treatment with endo‐1,3‐ß‐glucanase and observed the fine structures of its surfaces by atomic force microscopy. The major matrix component was partially removed from the cell wall by glucanase, and the enzyme treatment significantly weakened the cell wall strength without affecting the pH dependence of cell wall extensibility. The enzymatic removal of the major matrix component by using a protease released polysaccharide containing glucose and glucuronic acid. This suggests that the major matrix component of the algal cell walls contains both proteins (or polypeptides) and polysaccharides consisting of glucose and glucuronic acid as the main constituents.     

Toward a biophysical theory of organogenesis: Birefringence observations on regenerating leaves in the succulent,Graptopetalum paraguayense E. Walther

Polarity shifts occur during organogenesis. The histological criterion for polarity is the direction of cell division. The biophysical criterion is the orientation of reinforcing cellulose microfibrils which lie normal to the organ axis and which determine the preferred growth direction. Using cell pattern to deduce cell lineage, and polarized light to study cellulose alignment, both aspects of polarity were examined in the epidermis of regenerating G. paraguayense. In this system new leaves and a stem arise from parallel cell files on a mature leaf. Large (90°) shifts in polarity occur in regions of the epidermis to give the new organs radial symmetry in the surface plane (files radiating from a pole). Study of the shifts in the epidermis showed that, during certain stages, shifts in the division direction are accompanied by shifts in the cellulose deposition direction, as expected. The new cellulose orientation is parallel to the new cross wall. During normal organ extension, however, shifts in division direction do not bring on changes in cellulose pattern. Thus the coupling between the two kinds of polarity is facultative. This variable relation is used in a biophysical model which can account for the reorganization of cell file pattern and cellulose reinforcement pattern into the radial symmetry of the new organ.     

Enzymatic modification of polysaccharides: Mechanisms,properties, and potential applications: A review

Polysaccharides are natural biopolymers found in almost all living organisms. They are used extensively in various industrial applications, such as food, adhesives, pharmaceuticals, and cosmetics. In many cases, their practical use is limited because of their weak solubility in neutral pH, their unsuitable hydrophilic/hydrophobic balance. In this context, chemical or enzymatic modification of their structure appears as a relevant way, to improve their properties, and thus to enlarge the field of their potential applications. Taking into account the reduction of the input energy and the environmental impact, and due to high specificity and selectivity properties, enzymatic bioprocesses have been investigated as attractive alternatives to toxic and non-specific chemical approaches. This review discusses the methods of enzymatic functionalization of four well-known polysaccharides, chitosan, cellulose, pectin and starch.Particular emphasis was placed on the methods, the reaction types and the enzymes implicated in the modification such as laccases, peroxidases lipases, tyrosinases, and transglutaminases. The impact of functionalization on the properties and the applications of polysaccharide derivatives were described.     

一株高效降解纤维素菌株的筛选及其产酶能力研究

目的 筛选并鉴定一种产纤维素酶能力较高的菌株,为纤维素的高效利用贮备菌源。方法 用羧甲基纤维素钠（CMC-Na）平板筛选产纤维素酶菌株,通过LB培养基对其进行纯化,16S rDNA基因序列分析其分类地位,3,5-二硝基水杨酸法（DNS）测定其产酶能力。结果 分离纯化得到的产纤维素酶菌株（S1）为芽胞杆菌属（Bacillus genus）的短小芽胞菌,在最佳产酶条件下产酶含量达到1 204 U/mL,产纤维素酶能力与里氏木霉（Trichoderma reesei）相当,但其产酶速率较里氏木霉低。结论 S1是一株产纤维素酶能力较高的菌株,产酶条件温和,初步鉴定为一种新种,具有较高研究及应用价值。     

Cellulase activity of a haloalkaliphilic anaerobic bacterium, strain Z-7026

Summary The cellulolytic activity of an alkaliphilic obligate anaerobic bacterium, Z-7026, which was isolated from the microbial community of soda-lake sediments and belongs to the cluster III of Clostridia with low G+C content, was studied. The bacterium was capable of growing in media with cellulose or cellobiose as the sole energy sources. Its maximal growth rate on cellobiose (0.042–0.046 h^–1) was observed at an initial pH value of 8.5–9.0, whereas the maximal rate of cellulase synthesis, assayed by using a novel fluorimetric approach, was found to be 0.1 h^–1 at pH 8–8.5. Secreted proteins revealed high affinity for cellulose and were represented by two major forms of molecular masses of 75 and 84 kDa, whereas the general protein composition of the precipitated and cellulose-bound preparations was similar to cellulosome subunits of Clostridium thermocellum. The optimum pH of the partially purified enzyme preparation towards both amorphous and crystalline cellulose was in the range 6–9, with more than 70% and less than 50% of maximal activity being retained at pH 9.2 and 5.0, respectively.     

Isolation of mutants of Talaromyces emersonii CBS 814.70 with enhanced cellulase activity

By a combination of genetic mutation and modification of growth medium the cellulase [see 1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4 etc.] activity of culture filtrates of Talaromyces emersonii CBS 814.70 has been increased four-fold to approximately 2 U ml^?1 and a productivity of 20–25 Ul^?1h^?1. At 50°C this system was completely stable for at least 24 h. At 60°C in static reaction mixtures 19% of the original activity was lost compared with 21% when mixtures were shaken. At 70°C the loss of activity after 4 h was 64% without shaking and 70% when shaken. The cellulase system from Trichoderma reesei was decidedly less stable than that of Talaromyces emersonii under each of the above conditions. The ability of each enzyme system, separately and together, to digest beet pulp was investigated.     

新型能源纤维素丁醇产业化发展现状及前景分析

纤维素丁醇作为一种新型可再生能源,具有与汽油配伍性好、蒸汽压较低、安全系数高、能量密度高及抗爆性好等优势,在替代化石燃料方面极具发展前景,已受到广泛关注。虽然纤维素丁醇工业化生产仍存在一定的技术瓶颈,生产技术经济性也较差,产业化发展受到限制,但未来通过政策支持,在丰富的农林剩余物资源及巨大市场需求的条件下,纤维素丁醇作为新型能源仍具有非常广阔的发展前景。为了更好地促进纤维素丁醇产业发展,以纤维素丁醇的产业化发展为研究对象,总结了纤维素丁醇产业发展现状,分析了纤维素丁醇产业发展过程中存在的问题,从政策、资源及市场等方面对未来纤维素丁醇产业发展的前景进行了预测,并对如何促进其产业化发展提出了建议。