裙带菜原生质体的分离和培养

本文以裙带菜(Undaria pinnatifida(Harv.)Suringar)为材料,进行原生质体分离和培养研究。取得以下结果: 1、使用海螺酶(sea snail enzymes)和纤维素酶(cellulase,Onozuka R-10),酶解裙带菜细胞壁,在一定的条件下,能够大量地分离成活的裙带菜原生质体。 2、实验表明,氯化钠可作为分离裙带菜原生质体研究中的一种理想的渗透刑。 3、荧光增白剂染色镜检法可作为鉴定裙带菜原生质体的一种辅助方法,并适用于原生质体再生壁的观察。 4、光照(2000—2500Lux)能促使原生质体再生细胞壁,含有蔗糖(W/V,1％)的培养液有助于原生质体再生细胞壁。 5、分离的裙带菜原生质体,经培养,已能长成幼体。     

Influence of nutritional stress on digestive enzyme activities in juveniles of two marine clam species, Ruditapes decussatus and Venerupis pullastra

The potential use of digestive activities as indicators of the nutritional status in bivalves is discussed in relation to the results obtained in two clam species exposed to starvation and refeeding. Activities of some digestive enzymes (amylase, laminarinase, cellulase, and protease) were measured in juveniles of two commercially interesting species of clams, Ruditapes decussatus and Venerupis pullastra. The specimens were fed normally, being after subjected to a 15-days starvation and a further refeeding period. Samples were obtained at different moments of such feeding schedule to evaluate enzymes as well as weight (live, dry and organic) and length, in order to calculate growth rates and feeding efficiencies. Starvation led to a major decrease in clam growth as measured by dry weight and a negative growth as measured by organic weight, this coinciding with a certain degree of growth of the shell and a consumption of soft tissue. This response occurred more rapidly in R. decussatus but was of a lower magnitude than in V. pullastra. Activity of carbohydrases decreased rapidly in both species with starvation, although protease activity was maintained in R. decussatus. Recovery after the end of starvation was not similar in both species; while R. decussatus attained similar growth rates and enzyme activities to those measured prior to nutritional stress, V. pullastra only recovered 50% of its initial values. For both species of bivalves it can be concluded that digestive enzymes, and more specifically amylase, could be used as indicative of their nutritional condition.     

Tracing of Peroxidase Activity in Humic Lake Water

An enzyme assay was developed for studies on peroxidase activities in humic lake water. 3,4-Dimethoxybenzyl alcohol (veratryl alcohol, VeraOH) was used as tracer substrate, and peroxidase (EC 1.11.1.7) activity was measured by high-performance liquid chromatography. The chemical stability of VeraOH and its application as peroxidase substrate was tested under light and dark conditions, different hydrogen peroxide (H₂O₂) concentrations and humic matter contents. VeraOH was stable under low UV radiation at in situ conditions in lake water (<0.010...0.25 kJ m^–2 d^–1), laboratory conditions (<0.05...0.30 kJ m^–2 d^–1), and low (1...100 μM) H₂O₂ concentrations. However, peroxides oxidized VeraOH above 1...10 mM H₂O₂ concentration in sterile Millipore-Q and humic lake water. Dark incubations showed little VeraOH oxidation products. The developed peroxidase assay was tested in the growth medium of Phanerochaete chrysosporium and a bacteria isolate (P.M.D. 20.4.3.1) from mesohumic lake Pääjärvi. Peroxidase activities were also measured in natural microbial communities under standard laboratory and under in situ conditions in humic lake water. Incubation times of about 5 to 12 days were usually needed to record significant (P < 0.05) peroxidase activities, in lake waters. In situ peroxidase activities varied in pelagial surface water (0...0.5 m) on a seasonal scale between 74 nmol L^–1 h^–1 and 273 nmol L^–1 (mean: 176 nmol L^–1 h^–1) and within the water column between 110 nmol L^–1 h^–1 and 800 nmol L^–1 h^–1 (mean: 500 nmol L^–1 h^–1) in polyhumic lake Mekkojärvi.     

Enzyme leach anomalies associated with deep Mississippi Valley-type zinc ore bodies at the Elmwood Mine, Tennessee

Deeply buried Mississippi Valley-type deposits that have been or are currently being mined in North America were initially discovered by drilling. Conventional geochemical methods are ineffective for detecting these ‘blind' deposits when they occur deep within sequences of stable-platform carbonates and shales. The ‘enzyme' leach is a selective analytical technique for determining trace elements associated with amorphous Mn oxide coatings in soils. In many areas of the world, the enzyme leach method is useful for detecting low-level geochemical anomalies in soils, which are associated with blind mineral deposits. Enzyme leach analysis of soils, collected at the Elmwood Mine, Tennessee, revealed high-contrast anomalies over ore bodies 370 m below the surface. In areas where the soils are in chemical equilibrium, ‘combination' anomalies occur over Zn ore bodies. These are characterized by asymmetrical halogen halos which occur around a halogen ‘central low'. Commodity metals (Zn and Pb) and trace elements associated with the ore (Cd, Ba, and Mn) form apical anomalies, which occur over the ore bodies and within the halogen halo. Under most circumstances, agricultural practices do not affect enzyme leach results. However, agricultural activity in central Tennessee appears to have altered the proportion of amorphous Mn oxides in the soils in some locations. Where the MnO₂-form equilibrium of the soil has been disturbed, enzyme leach data are erratic. In the one instance where this was encountered, ratioing the data to Mn reveals anomalies which bracket the blind ore bodies.     

A comparative analysis of enzyme leach and mobile metal ion selective extractions; case studies from glaciated terrain, northern Ontario

The enzyme leach and MMI (mobile metal ion) selective digestions are rapidly gaining popularity in the exploration community because of their successful track record in non-glaciated, arid and tropical climatic regions. Few successful case studies from high-latitude, temperate regions have been published to date. Also lacking is a comprehensive discussion of the constraints and limitations of these geochemical methods and how they affect the successful interpretation of selective-leach survey results in glaciated regions. This paper evaluates each method using specific examples from four case studies undertaken in the glaciated region of northern Ontario. The case studies clearly demonstrate that both the MMI and enzyme leach selective digestions provide the explorationist with useful information, which, when used in conjunction with other exploration tools, can assist with the identification of potential diamond drill targets. Notwithstanding this, the techniques do not appear to work well as ‘stand alone' methods. The importance of following strict sampling protocols and obtaining high-quality observational information on the sampling site and media collected cannot be overstressed. It is only by filtering out the many variables that arise in any sampling program that a sound interpretation of the data can be made. The case studies have drawn attention to some of the apparent shortfalls of the techniques. Of these, issues such as the ability to reproduce survey results from year to year and the recognition of anomalous element associations which specifically target blind mineralisation are probably those which require significant follow-up work. Clearly, additional case studies are required from the glaciated regions of the world to assist with the optimisation of geochemical response of MMI and enzyme leach selective extractions. The mechanisms responsible for the formation of surface geochemical anomalies over deeply buried mineralisation are not well understood. The observed patterns of geochemical response in surface soils and both shallow and deep ground waters over concealed mineralisation should assist with the development of new dispersion models.     

水体磷酸酶:来源、特征及其生态学意义

酶在水生态系统的物质循环与能量转化过程中具有关键作用。本文以湖泊磷酸酶为例了水环境中酶的来源,特下及其生态学意义。酶主要源于细菌,浮游植物和浮游动物,且能以胞外的或溶解态的形式存在。     

Application of fluorescence spectroscopic techniques and probes to the detection of biopolymer degradation in natural environments

The activities and substrate specificities of extracellular enzymes in natural systems are not well understood, despite their critical role in microbial remineralization of organic carbon. These enzymes initiate organic carbon degradation by selectively hydrolyzing high molecular weight substrates to lower molecular weight products which can be transported into cells. A set of single- and dual-labeled fluorescent polysaccharides was synthesized and characterized to explore a variety of approaches for measuring enzymatic hydrolysis of biopolymers via photophysical techniques, focusing particularly on rapid and robust optical techniques which are amenable to field measurements in remote locales. A shotgun-labeling approach yielded dual-labeled probes that exhibited substantial donor fluorophore quenching. The photophysical response of these probes to hydrolysis via purified enzymes was investigated in the lab, and fluorescence polarization proved to be a rapid and reliable technique for monitoring probe hydrolysis. Initial field results were also obtained from hydrolysis experiments in sediment porewaters. Because polarization measurements are rapid and simple, this approach could be used to follow the extracellular enzymatic hydrolysis of a wide range of biopolymers which fuel microbial metabolism.