Effect of fossil diatoms on the growth of two syngeneic murine leukemias

The effect of micronized frustules of fossil diatoms (DS) on tumor growth and survival of mice receiving an ip inoculations of either a spontaneous lymphoblastic leukemia (LB) or P-388 lymphocytic leukemia (P-388) was investigated. A multi-dose study was designed, mice receiving 1000, 100, 10 and 1 μg of a suspension of DS, either ip or sc on day 1, 4 and 9 after tumor inoculation. With LB the best results were observed when DS were inoculated by the ip route, no effect being observed with the sc route. The best therapeutic effect resulted with 1 μg DS: 33% of the mice were alive 24 days after tumor inoculation, when all the controls had died. With P-388, only a temporary effect with the 10 μg DS dose was observed. In no case was it possible to prolong survival. It is concluded that at low doses of DS therapeutic effect is greatest, while toxicity due to SiO₂ is greatly reduced.     

Identification of two Skeletonema costatum-like diatoms by fluorescence in situ hybridization

A harmful algae bloom (HAB) is a dense aggregation of algae in a marine or aquatic environment that can result in significant environmental problems. To forecast the occurrence of HAB, development of a rapid and precise detection method is urgently required. In this study, two Skeletonema costatum-like diatoms (SK-1 and SK-2), were identified morphologically under a light microscope, and detected using fluorescent in situ hybridization (FISH). Strain SK-1 was isolated from a frequently HAB affected area of the East China Sea, and strain SK-2 from an aquatic farm in Qingdao, China. Fluorescent DNA probes were designed that were complementary to the ITS sequence (including 5.8S rDNA) of strain SK-1. After hybridization, strong green fluorescence was observed in cells of strain SK-1 under an epifluorescence microscope; however, no such fluorescence was observed with strain SK-2, which indicates that probes hybridized only the DNA of the target strain, SK-1, in species-specific manner, and that the two strains do not belong to a same species. This finding was confirmed by ITS sequence analysis. The FISH technique used in this study was sensitive, simple, and rapid, and is a promising tool for detecting target HAB species in natural environments.     

Identification of two Skeletonema costatum-like diatoms by fluorescence in situ hybridization

A harmful algae bloom (HAB) is a dense aggregation of algae in a marine or aquatic environment that can result in significant environmental problems. To forecast the occurrence of HAB, development of a rapid and precise detection method is urgently required. In this study, two Skeletonema costatum-like diatoms (SK-1 and SK-2), were identified morphologically under a light microscope, and detected using fluorescent in situ hybridization (FISH). Strain SK-1 was isolated from a frequently HAB affected area of the East China Sea, and strain SK-2 from an aquatic farm in Qingdao, China. Fluorescent DNA probes were designed that were complementary to the ITS sequence (including 5.8S rDNA) of strain SK-1. After hybridization, strong green fluorescence was observed in cells of strain SK-1 under an epifluorescence microscope; however, no such fluorescence was observed with strain SK-2, which indicates that probes hybridized only the DNA of the target strain, SK-1, in species-specific manner, and that the two strains do not belong to a same species. This finding was confirmed by ITS sequence analysis. The FISH technique used in this study was sensitive, simple, and rapid, and is a promising tool for detecting target HAB species in natural environments.     

Classification of marine diatoms using pigment ratio suites

Diatoms are widely distributed in many temperate areas and some species frequently form extensive blooms in spring. Hence, monitoring the variations of specific genera or species of diatoms is necessary for studying phytoplankton population dynamics in marine ecosystems. To test whether pigment ratios can be used to identify diatoms at a below-class taxonomic level, we analyzed 14 species/strains of diatoms isolated from Chinese seas using high performance liquid chromatography (HPLC). We normalized all pigment concentrations to total chlorophyll a to calculate the ratios of pigment to chlorophyll a, and calculated the ratios between accessory pigments (or pigment sums). Cluster analysis indicated that these diatoms could be classified into four clusters in terms of three accessory pigment ratios: chlorophyll c2: chlorophyll c1, fucoxanthin:total chlorophyll c and diadinoxanthin:diatoxanthin. The classification results matched well with those of biological taxonomy. To test the stability of the classification, pigment data from one species, cultured under different light intensities, and five new species/strains were calculated and used for discriminant analysis. The results show that the classification of diatom species using pigment ratio suites was stable for the variations of pigment ratios of species cultured in different light intensities. The introduction of new species, however, may confuse the classification within the current scheme. Classification of marine diatoms using pigment ratio suites is potentially valuable for the fine chemotaxonomy of phytoplankton at taxonomic levels below class and would advance studies on phytoplankton population dynamics and marine ecology.     

Studies on culture conditions of benthic diatoms for feeding abalone

Effects of iron and silicon nutrients and of orthogonal combinations of nitrogen, phosphorus, iron and silicon on the growth rate of three benthic diatoms were studied by using an in situ OD measurement method. The results of monofactor tests of iron and silicon showed that Fe-EDTA was better than ferric citrate in the culture of these diatoms; that the favourable concentration of Fe-EDTA was about 0.5 mg/L of Fe and that of silicate was 2.5 mg/L of Si or more. The orthogonal test showed that the optimal concentration ratios (mg/L) of nitrogen, phosphorus, iron and silicon were: 5.0: 0.25: 0.5: 2.0 forCocconeis scutellum var.parva; 2.5: 1.0: 1.0: 2.0 forAmphora coffeaeformis; and 5.0: 0.15: 0.5: 2.0 forN. mollis. Project 39470065 supported by NSFC.     

Studies on culture conditions of benthic diatoms for feeding abalone

Effects of salinity, pH, nitrogenous and phosphate nutrients on the growth rate of four species of benthic diatoms were studied by using the method of in situ optical density measurement. The optimal culture conditions for the four species of diatoms are as follows: forAmphora coffeaeformis, s 35; pH 8.5; NO₃ ⁻−N 1.54, NH₄ ⁺−N, 7.0; CO (NH₂)₂−N, 2.5 (mg/L); PO₄ ³⁻−P 1.13 (mg/L); forCocconeis scutellum varparva, s 30; pH 8.5; NO ₃ ⁻ −N 3.08, NH ₄ ⁺ −N 3.5, CO(NH₂)₂−N 5.0 (mg/L); pO ₄ ³⁻ −P 0.283 (mg/L); forNavicula corymbosa s 25; pH 8.0; NO ₃ ⁻ −N 1.54, NH ₄ ⁺ −N 3.5 CO(NH₂)₂−N 5.0 (mg/L); PO ₄ ³⁻ −P 0.565 (mg/L); forNavicula mollis. s 25; pH 8.0; NO ₃ ⁻ −N 1.54, NH ₄ ⁺ −N 1.75, CO(NH₂)₂−N 1.25 (mg/L); PO ₄ ³⁻ −P 0.141 (mg/L). Part of the results of this paper were exchanged in the Fourth Asian Aquaculture Forum. Oct. 16–20. 1995. Beijing, P. R. China.     

测震井下观测压制背景噪声特征分析

利用赤峰台井下和山洞观测、二连浩特台井下和地表观测测震数据,通过计算其加速度PSD值和相应的PDF值及1~20 Hz频段RMS值,研究井下观测压制测震台站背景噪声的特征。结果表明,在大于2 Hz频段,井下观测相比于山洞和地表观测有显著的压制背景噪声特征,尤其在大于9 Hz频段压制背景噪声特征突出;在16 s~2 Hz频段,井下、山洞、地表观测测震台站背景噪声水平一致性较高,井下观测在该频段不能压制背景噪声;在低于16 s频段,井下观测相比于山洞和地表观测有一定的压制背景噪声特征。通过井下观测可有效降低测震台站背景噪声水平,从而提高观测数据质量。     

Total lipid and fatty acid composition of eight strains of marine diatoms

Fatty acid composition and total lipid content of 8 strains of marine diatoms (Nitzschia frustrula, Nitzschia closterium, Nitzschia incerta, Navicula pelliculosa, Phaeodactylum tricornutum, Synedra fragilaroides) were examined. The microalgae were grown under defined conditions and harvested at the late exponential phase. The major fatty acids in most strains were 14∶0 (1.0%–6.3%), 16∶0 (13.5–26.4%), 16∶1n−7 (21.1%–46.3%) and 20∶5n−3 (6.5%–19.5%). The polyunsaturated fatty acids 16∶2n−4, 16∶3n−4, 16∶4n−1 and 20∶4n−6 also comprised a significant proportion of the total fatty acids in some strains. The characteristic fatty acid composition of diatoms is readily distinguishable from those of other microalgal groups. Significant concentration of the polyunsaturated fatty acid 20∶5n−3 (eicosapentaenoic acid) was present in each strain, with the highest proportion in B222 (19.5%). Project supported by the Hi-Tech “863” Programs of the China Ministry of Science and Technology (863-819-02-01).     

Inhibition of fish nodavirus by gymnemagenol extracted from Gymnema sylvestre

Viral nervous necrosis(VNN)has emerged to become a major problem in the culture of larval and juvenile marine fish worldwide.Bioactive phytochemicals isolated from commonly available medicinal plants are often screened for their efficacy in controlling fish viral diseases.Occurrence of newer viral strains and resistance to existing antiviral drugs are problems currently as-sociated with treatment of VNN,which necessitates looking for alternate sources for effective antiviral drugs.The aim of the present study was to screen antiviral potential of gymnemagenol(C30H50O4)previously extracted from leaves of Gymnema sylvestre.The fish nodavirus,grouper nervous necrosis virus(GNNV)in infected Sahul Indian Grouper Eye(SIGE)cell lines were used to study the antiviral activity of gymnemagenol under in vitro conditions.The susceptibility of the virus to gymnemagenol was confirmed by measuring the viral titre(TCID50 mL?1)in virus-infected SIGE cells every 24 h.Gymnemagenol at 20 μg mL?1 inhibited the prolifera-tion of GNNV to 53% at the end of the 6th d by inhibiting the proliferation of GNNV-infected SIGE cells.The viable SIGE cells were reduced to 47% as determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay.The viral titre(TCID50 mL?1)was also reduced to log 2.8 at the end of the 7th d in gymnemagenol-treated SIGE cells after inoculated with GNNV when compared to untreated control SIGE cell viral titre(log 4.1).Based on our results it can be concluded that gymnemagenol could be used as an antiviral agent against GNNV infection.     

Impacta of CO2 enrichment on growth and photosynthesis in freshwater and marine diatoms

The physiological responses of Nitzschia palea Kiitzing, a freshwater diatom, to elevated CO2 were investigated and compared with those of a marine diatom, Chaetoceros muelleri Lemmermann previously reported. Elevated CO2 concentration to 700 μl/L increased the dissolved inorganic carbon (DIC) and lowered the pH in the cultures of N. palea, thus enhancing the growth by 4%-20% during the whole growth period. High CO2-grown N. palea cells showed lower levels of dark respiration rates and higher Ik values. Light-saturated photosynthetic rates and photosynthetic efficiencies decreased in N. palea with the doubling CO2 concentration in airflow to the bottom of cultures, although the doubling CO2 concentration in airflow to the surface cultures had few effects on these two photosynthetic parameters. N. palea cells were found to be capable of using HCO3- in addition to gaseous CO2, and the CO2 enrichment decreased their affinity for HCO3- and CO2. Although doubled CO2 level would enhance the biomass of N. palea and C. muelleri to different extents, compared with the marine diatom, it had a significant effect on the specific growth rates of N. palea. In addition, the responses of photosynthetic parameters of N. palea to doubled CO2 concentration were almost opposite to those of C. muelleri.     

Effect of growth phase on the fatty acid compositions of four species of marine diatoms

The fatty acid compositions of four species of marine diatoms (Chaetoceros gracilis MACC/B13, Cylindrotheca fusiformis MACC/B211, Phaeodactylum tricornutum MACC/B221 and Nitzschia closterium MACC/B222), cultivated at 22 ℃±1 ℃ with the salinity of 28 in f/2 medium and harvested in the exponential growth phase, the early stationary phase and the late stationary phase, were determined. The results showed that growth phase has significant effect on most fatty acid contents in the four species of marine diatoms. The proportions of 16:0 and 16: 1n-7 fatty acids increased while those of 16 :3n-4 and eicosapentaenoic acid (EPA) decreased with increasing culture age in all species studied. The subtotal of saturated fatty acids (SFA) increased with the increasing culture age in all species with the exception of B13. The subtotal of monounsaturated fatty acids (MUFA) increased while that of polyunsaturated fatty acids (PUFA) decreased with culture age in the four species of marine diatoms. MUFA reached their lowest value in the exponential growth phase, whereas PUFA reached their highest value in the same phase.     

Inhibition of norsolorinic acid accumulation to Aspergillus parasiticus by marine actinomycetes

Thirty-six strains of marine actinomycetes were isolated from a sample of marine sediment collected from the Yellow Sea and evaluated in terms of their inhibitory activity on the growth of Aspergillus parasiticus and the production of norsolorinic acid using dual culture plate assay and agar diffusion methods. Among them, three strains showed strong antifungal activity and were subsequently identified as Streptomyces sp. by 16S rRNA gene sequencing analysis. The supernatant from the fermentation of the MA01 strain was extracted sequentially with chloroform and ethyl acetate, and the activities of the extracts were determined by tip culture assay. The assay results show that both extracts inhibited mycelium growth and toxin production, and the inhibitory activities of the extracts increased as their concentrations increased. The results of this study suggest that marine actinomycetes are biologically important for the control of mycotoxins, and that these bacteria could be used as novel biopesticides against mycotoxins.     

Inhibition of Aspergillus parasiticus and cancer cells by marine actinomycete strains

Ten actinomycete strains isolated from the Yellow Sea off China's coasts were identified as belonging to two genera by 16 S r DNA phylogenetic analysis: Streptomyces and Nocardiopsis. Six Streptomyces strains(MA10, 2SHXF01-3, MA35, MA05-2, MA05-2-1 and MA08-1) and one Nocardiopsis strain(MA03) were predicted to have the potential to produce aromatic polyketides based on the analysis of the KSα(ketoacyl-synthase) gene in the type II PKS(polyketides synthase) gene cluster. Four strains(MA03, MA01, MA10 and MA05-2) exhibited significant inhibitory effects on mycelia growth(inhibition rate 50%) and subsequent aflatoxin production(inhibition rate 75%) of the mutant aflatoxigenic Aspergillus parasiticus NFRI-95. The ethyl acetate extracts of the broth of these four strains displayed significant inhibitory effects on mycelia growth, and the IC50 values were calculated(MA03: 0.275 mg m L-1, MA01: 0.106 mg m L-1, MA10: 1.345 mg m L-1 and MA05-2: 1.362 mg m L-1). Five strains(2SHXF01-3, MA03, MA05-2, MA01 and MA08-1) were selected based on their high cytotoxic activities. The ethyl acetate extract of the Nocardiopsis strain MA03 was particularly noted for its high antitumor activity against human carcinomas of the cervix(He La), lung(A549), kidney(Caki-1) and liver(Hep G2)(IC50: 2.890, 1.981, 3.032 and 2.603 μg m L-1, respectively). The extract also remarkably inhibited colony formation of He La cells at an extremely low concentration(0.5 μg m L-1). This study highlights that marine-derived actinomycetes are a huge resource of compounds for the biological control of aflatoxin contamination and the development of novel drugs for human carcinomas.     

Distribution patterns of benthic diatoms during summer in the Niyang River, Tibet, China

The aim of this study was to investigate the distribution, density, community structure and biodiversity characteristics of benthic diatoms, and to analyze whether differences in species composition and abundance exist in different regions of the Niyang River, Tibet. Among the 157 taxa observed in 15 sampling sites in the main river and tributary, most were casual species (>100), the relative abundance of the genera Achnanthes and Fragilaria was 67% of the total relative abundance. Achnanthes minutissima was the most important species and dominated the whole river reaches (average relative abundance was 30%); the average diatom densities were 7.4 × 10⁵ cell/cm² at all sites, and increased slowly from the upper section to downriver. The significant indicator taxa with higher relative abundance were Achnanthes biasolettiana (18.0%) and Fragilaria arcus (18.2%), Fragilaria capucina var. vaucheriae (31.2%), Fragilaria construens var. venter (11.3%) and Cymbella affinis (11.0%) in the upper, tributary and mid-river sections, respectively. Achnanthes minutissima was the most abundant species (56%) in the downriver section. Biodiversity indices showed a gradual decrease from the up- to down-river section, and dominant species were more abundant in the upper and mid-river sections than in the downriver section. A two-way indictor species analysis (TWINSPAN) of diatom composition clearly showed four different groups, namely the upper, mid, lower and tributary sections. Detrended correspondence analysis (DCA) supported the results of TWINSPAN, and the characteristics of site distribution and species composition in the Niyang River supported the spatial structure of diatom assemblages. This study indicates that bio-assessment programs utilizing benthic diatoms could clearly benefit lotic water with regional stratification.     

Growth inhibition and oxidative stress in two species of marine diatoms exposed to 1-phenylethanol

1-phenylethanol(1-PEA)is a flavor extensively used in the production of co smetics,beverages,and food.The release of 1-PEA into coastal environments has aroused great concern.However,its potential effects on marine organisms are still unknown.In order to provide a better understanding of the ecological risks of 1-PEA in marine environments,this study determined the toxic effects of 1-PEA on two marine diatoms(Phaeodactylum tricornutum and Skeletonema costatum).The diatoms were grown in culture medium containing different concentrations of 1-PEA for 96 h.The contents of chlorophyll a,chlorophyll c,glutathione(GSH),malondialdehyde(MDA),and the activities of superoxide dismutase(SOD),catalase(CAT)and glutathione peroxidase(GPx),were measured at the end of the exposure period.1-PEA was shown to significantly inhibit the growth of diatoms,with 96-h EC_(50) values of 257.14 mg/L and 126.46 mg/L in P.tricornutum and S.costatum,respectively.In P.tricornutum,the levels of SOD,CAT,GPx,GSH,and MDA were stimulated only when 1-PEA concentrations were close to or greater than the 96-h EC_(50)value.However,in S.costatum,the activities of SOD and CAT,and the syntheses of two chlorophylls were inhibited even at an exposure concentration below the 96-h EC_(50) value.Taken together,these findings indicate a potential ecological risk by discharging 1-PEA into coastal areas and its species-specific toxic effects on marine organisms.     

Preliminary investigations on fossil diversity variation of Mesozoic Marattialean ferns in China

The Marattiales is one of the oldest lineages of vascular plants with extensive fossil records dated back to the Carboniferous. Understanding the fossil diversity variation and distribution pattern is helpful for exploring the evolutionary history of this fern group. In this work, the preliminary analysis of diversity change and distribution of the Mesozoic Marattialean fossil records in China are reported covering the Triassic and Jurassic periods based on available published data. In addition, a brief discussion is made regarding to the potential causes for these variation and distribution of this fern group.     

Preliminary investigations on fossil diversity variation of Mesozoic Marattialean ferns in China

The Marattiales is one of the oldest lineages of vascular plants with extensive fossil records dated back to the Carboniferous. Understanding the fossil diversity variation and distribution pattern is helpful for exploring the evolutionary history of this fern group. In this work, the preliminary analysis of diversity change and distribution of the Mesozoic Marattialean fossil records in China are reported covering the Triassic and Jurassic periods based on available published data. In addition, a brief discussion is made regarding to the potential causes for these variation and distribution of this fern group.     

A preliminary investigation of fossil wood from Lower Mekong Basin of Southeast Asia

Nine fossil wood samples from the Mesozoic bedrock and the Quaternary terrace deposits of the Lower Mekong Basin in Southeast Asia including Thailand , Laos and Cambodia were investigated in order to assist in developing a hypothesis about the Mekong River palaeocourses .Six of the samples were conifers assigned to Aga-thoxylon sp., and three were dicots of cf .Pahudioxylon sp.and two unknown taxa ( Dicotyloxylon sp.) . The preservation of two dicotyledonous wood samples is insufficient for precise identification to family level , such that the samples are not suitable with respect to investigation of the river palaeocourse .However , these findings increase the systematic data of the fossil wood from the Mekong Basin .Further investigations of fossil wood from the Mekong Basin are in progress to gain a regional perspective on the plant communities and to form better reconstruction of the palaeoenvironment .