Tang Xue-xi

Physiological and ultralstructural changes of Chlorella sp. induced by UV-B radiation

In order to investigate the mechanisms of enhanced UV-B radiation on algae, the effects of UV-B radiation on the physiological and ultrastructural changes of Chlorella sp. were examined. The results showed that UV-B radiation could inhibit the growth and photosynthesis of microalgae. UV-B radiation at lower doses increased the photosynthetic pigment (chlorophyll a (Chla) and carotenoid (Car)) contents, while at higher doses of UV-B radiation Chla and Car contents were decreased. The ultrastructure of Chlorella sp. without exposure to UV-B showed that the thylakoid lamellae were clear and regular, the stroma of its chloroplast was apparent and clear. The globules with photosynthetic pigments and the cristae of mitochondria were clearly seen. After exposure to UV-B radiation at dose of 2.88 kJ/m2, the thylakoid lamellae of Chlorella sp. were lost and dissolved, the globules which contained photosynthetic pigments in chloroplast were bleached; some mitochondria cristae were dissolved; slight plasmolysis was found in some Chlorella sp. cells. After exposure to 5.76 kJ/m2 UV-B radiation, the thylakoid was in disarray and disintegration, plasmolysis was found in most cells, and the cell wall was broken and began to fall out. Many blank areas were observed in cells, mitochondria were seriously deformed and most of the mitochondria cristae were dissolved. Also, globules containing photosynthetic pigments in chloroplast were bleached and some empty globules were found in chloroplast. Therefore, UV-B radiation could damage cell structure of Chlorella sp., and this damage increased with the dose of UV-B radiation they exposed to.

Effect of UV-B radiation on ingesting and nutritional selecting behavior of rotifer Brachionus urceus

Effect of UV-B radiation on ingesting and nutritional selecting behavior of the roifer Brachionus urceus on 5 species of micro-algae were studied under controlled laboratory conditions. Results showed that enhanced UV-B radiation significantly inhibited ingesting of the rotifer B. urceus when it was fed with 5 species of micro-algae (p<0.05). The ingesting selectivity rate varied with the UV-B radiation enhancement when it was fed with 5 species micro-algal mixture. Results indicated that the enhanced UV-B radiation could affect ingesting and nutritional selectivity of B. urceus.

Antioxidant and isozyme features of two strains of Laminaria japonica (Phaeophyceae)

Healthy sporophytes of two gametophyte mutants of Laminaria japonica with different heat resistances: kelp 901 (901, with comparatively stronger heat-resistance) and Rongcheng No.1 (RC, sensitive to heat stress), were respectively collected during October to December 2002 from Yantai and Rongcheng Sea Farm in the Shandong Peninsula of China. The contents of some biochemical materials and antioxidant capacity were analyzed under controlled laboratory conditions to identify if there is any relation between the overall antioxidant capacity and the heat-resistance in L. japonica and to understand possible mechanism of heat-resistance. Results show that: (1) the overall antioxidant capacity in healthy sporophyte of 901, such as vitamin E, polyphenol, and ascorbic acid contents and the enzymatic activity of SOD, POD, CAT, Gpx, PPO, and PAL, were not always higher than that of RC under controlled laboratory conditions, and no significance (P>0.05) was shown in total antioxidant capacity (T-AOC) in 901 and RC. Result suggested that the difference in antioxidant capacity was not a decisive factor for different heat-resistances in L. japonica; (2) the simultaneous assay on isozymes was carried out using vertical polyacrylamide gel electrophoresis (PAGE). Considerable differences in peroxide (PRX), malate dehydrogenase (MDH), malic enzyme (ME), polyphenol oxidase (PPO) and glutamate dehydrogenase (GDH) were obtained in 901 and RC from either the band number, relative mobility (Rf), or staining intensity, and ME could be used as an indicator to distinguish healthy sporophyte of 901 and RC under controlled laboratory conditions.

Preparation and characterizationin vitro of sustained-release captopril/Chitosan-gelatin net-polymer microspheres (Cap/CGNPMs)

The captopril/Chitosan-gelatin net-polymer microspheres (Cap/CGNPMs) were prepared using Chitosan (CS) and gelatin (Gel) by the methods of emulsification. A cross linked reagent alone or in combination with microcrystalline cellulose (MCC) was added in the process of preparation of microspheres to eliminate dose dumping and burst phenomenon of microspheres for the improvement of the therapeutic efficiency and the decrease of the side effects of captopril (Cap). The results indicate that Cap/CGNPMs have a spherical shape, smooth surface morphology and integral inside structure and no adhesive phenomena and good mobility, and the size distribution is mainly from 220 to 280 μm. Researches on the Cap release test in vitro demonstrate that Cap/CGNPMs are of the role of retarding release of Cap compared with Cap ordinary tablets (COT), embedding ratio (ER), drug loading (DL), and swelling ratio (SR), and release behaviors of CGNPMS are influenced by process conditions of preparation such as experimental material ratio (EMR), composition of cross linking reagents. Among these factors, the EMR(1/4), CLR (FOR+TPP) and 0.75% microcrystalline cellulose (MCC) added to the microspheres are the optimal scheme to the preparation of Cap/CGNPMs. The Cap/CGNPMs have a good characteristic of sustained release of drug, and the process of emulsification and cross-linking process is simple and stable. The CGNPMs is probable to be one of an ideal sustained release system for water-soluble drugs.

Notice of Retraction A study of distribution variation of chlorophyll a and regulatory effects of environmental factors in the Yellow Sea nearshore area of Shandong province

The concentration of Chlorophyll a and the values of environmental factors, were determined in the water collected from Yellow Sea nearshore area of Shandong province between August 2006 and October 2007. Results indicated that annually averaged concentration of chlorophyll a was 4.26 mg/m3 in the investigated sea areas, meanwhile there was a chlorophyll maximum in summer and a secondary maximum in spring. In general, the concentration of chlorophyll a gradually decreased from shore to offshore in spring, summer, winter, while opposite in autumn, and high (low) value areas of chlorophyll a horizontal distribution were alien within different seasons. The spatial-temporal distribution of environmental factors showed high heterogeneity(except pH), and the environmental factors exerted regulatory effects on the distribution of chlorophyll a in different extent. According to PCA and Bivariate correlation analysis, the most critical regulatory factor which determined the distribution of chlorophyll a was nutrients, especially nitrogen, next came phosphorus, silicon. The regulatory effects of dissolved oxygen and temperature was antagonistic with each other, while that of pH and total organic carbon was weak.

Preliminary studies on toxicity induced by yessotoxin(YTX) on Purkinje cells from the cerebellum of ICR mice

Yessotoxin(YTX) and its analogues are disulfated polyether compounds which have been concerned more in seafood quality monitoring and shellfish industries recently. Many studies on the toxicity of YTXs had been carried out,but the results showed apparent discrepancies. Just these discrepancies have encouraged many researchers to study the mechanism by which YTX exerts its action,such as what the target tissues are,what the pattern of the mode and precise mechanism of action are. However,the process still remains largely unclear. This paper aims to study the toxicity of yessotoxin and analyze the possible action mechanism to the nerve tissue by using histological and immunohistochemical methods. 24 hrs after tail intravenous injection with yessotoxin,the female ICR mice were killed and cerebella tissue was fixed and sliced. Hematoxylin-eosin(HE)staining used to study the effects of yessotoxin on nerve cells shows obvious morphological changes of Purkinji cells in cerebella tissue,such as shrinkage,deep staining of cytoplasm,non-mottled Nissl’s body and so on. According to the immunohistochemical staining of calcium binding protein S-100,there is a more positive response to YTX in test group than in control group. It seems that YTX induces the increase of Ca 2+ concentration in Purkinji cells of mice cerebellum; it is identical to the results of other researches.To our knowledge,this is the first report of the toxicity of YTX on nervous system in China,but the work is preliminary and further studies are needed,such as the relationship between the action mechanism of YTX and Ca 2+ signal transduction.