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At least 217 records · Page 12Linked to original sources
PubMed2006

Effect of methyl tert-butyl ether in standard tests for mutagenicity and environmental toxicity.

Methyl tert-butyl ether (MTBE) is a synthetic compound that is used as a technological solution to problems created by air pollution from vehicle emissions. An important source of MTBE in the environment is leakage from underground storage tanks at gasoline stations or accidents during gasoline transport. The aim of this study was to evaluate the risk of MTBE leakage for the environment using the Microtox (Vibrio fischeri) toxicity test, Lactuca sativa seed germination test, and Ames bacterial mutagenicity test with Salmonella typhimurium his(-) strains TA98, TA100, YG1041, and YG1042, using both standard plate and preincubation protocols. The result of Microtox expressed as EC(50) was 33 mg (MTBE)/L. The effect of all tested MTBE concentration (0.05, 0.50, and 1.00% v/v) on Lactuca sativa roots elongation was negative and proved its toxicity. The highest tested concentration of MTBE that could be tested in Ames test was 3 mg (MTBE)/plate, because of cytotoxicity. No mutagenic response was observed at this or lower concentrations in any of the four strains used.

Air Pollutants↗
PubMed2004

Genetic analysis and mapping of resistance to lettuce dieback: a soilborne disease caused by tombusviruses.

A diverse collection of modern, heirloom and specialty cultivars, plant introduction (PI) accessions, and breeding lines of lettuce were screened for susceptibility to lettuce dieback, which is a disease caused by soilborne viruses of the family Tombusviridae. Susceptibility was evaluated by visual symptom assessment in fields that had been previously shown to be infested with Lettuce necrotic stunt virus. Of the 241 genotypes tested in multiple field experiments, 76 remained symptom-free in infested fields and were therefore classified as resistant to dieback. Overall, resistant genotypes were as prevalent among modern cultivars as in heirloom cultivars or primitive germplasm. Within modern germplasm, however, all crisphead (iceberg) cultivars were resistant, while all romaine cultivars were susceptible. Using enzyme-linked immunosorbent assay, tombusviruses were detected in leaves of some plants of resistant genotypes that were grown in infested fields, suggesting that symptom-free plants are not immune to viral infection. The inheritance of resistance was studied for 'Salinas', a modern iceberg cultivar, and PI 491224, the progenitor of recently released romaine germplasm with resistance to lettuce dieback. Resistance was conferred by a dominant allele at a single locus in both genotypes. The tombusvirus resistance locus from 'Salinas', Tvr1, was mapped in an intraspecific Lactuca sativa population to a location that corresponds to linkage group 2 on the consensus map of Lactuca. The largest cluster of resistance genes in lettuce, the Dm1/Dm3 cluster, is found on this linkage group; however, the precise position of Tvr1 relative to this cluster has not yet been determined. To our knowledge, Tvr1 is the first tombusvirus resistance gene identified for any plant host.

Chromosome Mapping↗
PubMed2005

A detailed linkage map of lettuce based on SSAP, AFLP and NBS markers.

Molecular markers based upon a novel lettuce LTR retrotransposon and the nucleotide binding site-leucine-rich repeat (NBS-LRR) family of disease resistance-associated genes have been combined with AFLP markers to generate a 458 locus genetic linkage map for lettuce. A total of 187 retrotransposon-specific SSAP markers, 29 NBS-LRR markers and 242 AFLP markers were mapped in an F(2) population, derived from an interspecific cross between a Lactuca sativa cultivar commonly used in Europe and a wild Lactuca serriola isolate from Northern Europe. The cross has been designed to aid efforts to assess gene flow from cultivated lettuce into the wild in the perspective of genetic modification biosafety. The markers were mapped in nine major and one minor linkage groups spanning 1,266.1 cM, with an average distance of 2.8 cM between adjacent mapped markers. The markers are well distributed throughout the lettuce genome, with limited clustering of different marker types. Seventy-seven of the AFLP markers have been mapped previously and cross-comparison shows that the map from this study corresponds well with the previous linkage map.

Chromosome Mapping↗
PubMed2003

Phytotoxicity to and uptake of enrofloxacin in crop plants.

Phytotoxicity of enrofloxacin on crop plants Cucumis sativus, Lactuca sativa, Phaseolus vulgaris and Raphanus sativus was determined in a laboratory model: the effect of 50, 100 and 5000 microgl(-1) were evaluated after 30 days exposure by measuring post-germinative growth of primary root, hypocotyl, cotyledons and leaves. Concentrations between 50 and 5000 microgl(-1) induced both toxic effect and hormesis in plants, by significantly modifying both length of primary root, hypocotyl, cotyledons and the number/length of leaves. A toxic effect is induced by high concentration (5000 microgl(-1)), while hormesis occurs at low concentrations (50 and 100 microgl(-1)). A continuum between toxic effect and hormesis is found in the four plant species. Both toxic effect and hormesis can be related to an efficient plant drug uptake, in the order of microgg(-1). Plants are able to metabolize enrofloxacin into ciprofloxacin, as also happens in animals; Cucumis, Lactuca and Phaseolus biologically convert about one quarter of stored enrofloxacin. The ecological implication of enrofloxacin contamination in terrestrial environments is discussed.

Anti-Infective Agents↗
PubMed2005

Phylogenetic signal in AFLP data sets.

AFLP markers provide a potential source of phylogenetic information for molecular systematic studies. However, there are properties of restriction fragment data that limit phylogenetic interpretation of AFLPs. These are (a) possible nonindependence of fragments, (b) problems of homology assignment of fragments, (c) asymmetry in the probability of losing and gaining fragments, and (d) problems in distinguishing heterozygote from homozygote bands. In the present study, AFLP data sets of Lactuca s.l. were examined for the presence of phylogenetic signal. An indication of this signal was provided by carrying out tree length distribution skewness (g1) tests, permutation tail probability (PTP) tests, and relative apparent synapomorphy analysis (RASA). A measure of the support for internal branches in the optimal parsimony tree (MPT) was made using bootstrap, jackknife, and decay analysis. Finally, the extent of congruence in MPTs for AFLP and internal transcribed spacer (ITS)-1 data sets for the same taxa was made using the partition homogeneity test (PHT) and the Templeton test. These analytical studies suggested the presence of phylogenetic signal in the AFLP data sets, although some incongruence was found between AFLP and ITS MPTs. An extensive literature survey undertaken indicated that authors report a general congruence of AFLP and ITS tree topologies across a wide range of taxonomic groups, suggesting that the present results and conclusions have a general bearing. In these earlier studies and those for Lactuca s.l., AFLP markers have been found to be informative at somewhat lower taxonomic levels than ITS sequences. Tentative estimates are suggested for the levels of ITS sequence divergence over which AFLP profiles are likely to be phylogenetically informative.

Classification↗
PubMedDate not supplied

Microbiological determinations of some vegetables from the Xochimilco zone in Mexico City, Mexico.

Vegetables intake is widely recommended because of its high content of vitamins, minerals and fiber. However, the irrigation of these vegetables, using wastewaters that have received inadequate treatment often carries unseen microbial pollution that becomes a high risk potential for humans. In the present research, two of the most consumed fresh vegetables cultivated in Mexico City were analyzed, lettuce (Lactuca sativa) and Mexican coriander (Eryngium foetidum). These vegetables are commonly consumed raw. The vegetable choice and the disinfection's method were carried out by the application of two tests to two hundred people in an aleatory form. Similarly, vegetable sampling was carried out by means of a random sampling from the cultivated areas in a chosen "chinampa" (from Náhuatl or Aztec, chinamitl, bulrush or cattail stalks lattice for hydroponics cultivation). Vegetable samples were transferred, in dark plastic bags and in cool boxes at 4 +/- 1.5 degrees C, to the laboratory. Microbiological analysis for Salmonella typhi, mesophilic microorganisms, and fecal coliforms were done according to the "NOM-093SSA1-1994" (Mexico). Results obtained demonstrated that samples treated with the most preferred disinfectant, a colloidal silver based one, had a partial elimination of pathogenic microorganisms found in both vegetables lettuce (Lactuca sativa) and coriander (Eryngium foetidum) samples (mesophyllic microorganisms from 200,000 to 96,500 UFC/g and from 175,000 to 125,000 UFC/g and fecal coliforms from 75 to 0.43 NMP/g and from 150 to 2.10 NMP/g, respectively). Salmonella typhi for all samples gave a positive result. Therefore, it was recommended to the cultivators of the Xochimilco (Náhuatl or Aztec name that means "place where flowers bloom") zone, either stop using contaminated water for irrigation or to use more efficient methods in order to eliminate pathogenic microorganisms, such as diluted chlorine solutions made with commercial cotton clothing bleachers.

Agriculture↗
PubMed1997

Effects on growth and accumulation of zinc in six seaweed species.

Seaweed species from a coastal area contaminated by heavy metals (Sepetiba Bay) in Rio de Janeiro State (Brazil) presented different levels of Zn concentrations. In some species the levels were 20 times higher than that from a noncontaminated area. The present study was undertaken to investigate the capability of different species to tolerate and accumulate zinc. For this purpose six species, Ulva lactuca, Enteromorpha flexuosa, Padina gymnospora, Sargassum filipendula, Hypnea musciformis, and Spyridia filamentosa, were cultivated under laboratory semistatic conditions in five Zn concentrations in seawater, 10, 20, 100, 1000, and 5000 micrograms.liter-1 for a period of 21 days. All species died at 5000 micrograms.liter-1 of Zn, two species (U. lactuca and E. flexuosa) died at 1000 micrograms.liter-1, and one, H. musciformis, died with 100 micrograms.liter-1. The lowest concentration of Zn that presented growth inhibition in the six species was 20 micrograms.liter-1. The brown alga P. gymnospora presented the highest accumulation level of Zn, and H. musciformis the lowest level. The results of tolerance and accumulation under laboratory conditions, associated with field results, indicate the species of Padina and Sargassum as the best species for monitoring heavy metals in tropical coastal areas, and the potential use of their biomass to remove heavy metals from wastewaters.

Environmental Monitoring↗
PubMed1999

Evaluation of the contamination of marine algae (Seaweed) from the St. Lawrence River and likely to be consumed by humans.

The goal of the study was to assess the contamination of marine algae (seaweeds) growing in the St. Lawrence River estuary and Gulf of St. Lawrence and to evaluate the risks to human health from the consumption of these algae. Algae were collected by hand at low tide. A total of 10 sites on the north and south shores of the St. Lawrence as well as in Baie des Chaleurs were sampled. The most frequently collected species of algae were Fucus vesiculosus, Ascophyllum nodosum, Laminaria longicruris, Palmaria palmata, Ulva lactuca, and Fucus distichus. Alga samples were analyzed for metals (As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn), iodine, and organochlorines. A risk assessment was performed using risk factors (e.g., RfD of the U.S. EPA, ADI of Health Canada, etc.). In general, concentrations in St. Lawrence algae were not very high. This was especially true for mercury and the organochlorines, concentrations of which were very low or below detection limits. Consequently, health risks associated with these compounds in St. Lawrence algae were very low. Iodine concentration, on the other hand, could be of concern with regard to human health. Regular consumption of algae, especially of Laminaria sp., could result in levels of iodine sufficient to cause thyroid problems. For regular consumers, it would be preferable to choose species with low iodine concentrations, such as U. lactuca and P. palmata, in order to prevent potential problems. Furthermore, it would also be important to assess whether preparation for consumption or cooking affects the iodine content of algae. Algae consumption may also have beneficial health effects. Scientific literature has shown that it is a good source of fiber and vitamins, especially vitamin B12.

Environmental Exposure↗
PubMed2000

A comparison of Peronospora parasitica (Downy mildew) isolates from Arabidopsis thaliana and Brassica oleracea using amplified fragment length polymorphism and internal transcribed spacer 1 sequence analyses.

Amplified fragment length polymorphism (AFLP) fingerprints and internal transcribed spacer 1 (ITS1) sequences from 27 Peronospora parasitica isolates (collected from Arabidopsis thaliana or Brassica oleracea), 5 Albugo candida isolates (from the same hosts and from Capsella bursa-pastoris), and 1 Bremia lactucae isolate (from Lactuca sativa) were compared. The AFLP analysis divided the isolates into five groups that correlated with taxonomic species and, in most cases, with host origin. The only exception was a group consisting of A. candida isolates from both B. oleracea and C. bursa-pastoris. ITS1 sequence analysis divided the isolates into the same five groups, demonstrated the divergence between P. parasitica isolates from A. thaliana and B. oleracea, and, using previously published ITS1 sequences, clearly showed the relationship between A. candida isolates from different hosts.

Arabidopsis↗
PubMed1992

Regulatory sequences for expressing genes in oomycete fungi.

Promoter and terminator sequences from a range of species were tested for activity in the oomycetes, a group of lower fungi that bear an uncertain taxonomic affinity to other organisms and in which little is known of the sequences required for transcription. Transient assays, using the reporter gene beta-glucuronidase (GUS), were used to examine the function of these promoters and terminators in the plant pathogens Phytophthora infestans and P. megasperma f. sp. glycinea, and in the saprophytic water mold, Achlya ambisexualis. Oomycete promoters, isolated from the ham34 and hsp70 genes of Bremia lactucae and the actin gene of P. megasperma f. sp. glycinea, resulted in high levels of GUS accumulation in each of the three oomycetes. In contrast, little or no activity was detected when promoters from higher fungi (four ascomycetes and one basidiomycete), plants, and animals were tested. The terminator from the ham34 gene resulted in much higher levels of GUS accumulation than did others, although an oomycete terminator was not absolutely required for expression. Transcript mapping of RNA from stable transformants confirmed accurate initiation from the B. lactucae hsp70 promoter and termination within 3' ham34 sequences in P. infestans. Our results indicate that the transcriptional machinery of the oomycetes differs significantly from that of the higher fungi, but that enough conservation exists within the class to allow vectors developed from one oomycete species to be used for others.

Base Sequence↗
PubMed2006

Varying stable nitrogen isotope ratios of different coastal marsh plants and their relationships with wastewater nitrogen and land use in New England, USA.

The stable nitrogen isotope ratios of some biota have been used as indicators of sources of anthropogenic nitrogen. In this study the relationships of the stable nitrogen isotope ratios of marsh plants, Iva frutescens (L.), Phragmites australis (Cav.) Trin ex Steud, Spartina patens (Ait.) Muhl, Spartina alterniflora Loisel, Ulva lactuca (L.), and Enteromorpha intestinalis (L.) with wastewater nitrogen and land development in New England are described. Five of the six plant species (all but U. lactuca) showed significant relationships of increasing delta (15)N values with increasing wastewater nitrogen. There was a significant (P < 0.0001) downward shift in the delta (15)N of S. patens (6.0 +/- 0.48 per thousand) which is mycorrhizal compared with S. alterniflora (8.5 +/- 0.41 per thousand). The downward shift in delta (15)N may be caused by the assimilation of fixed nitrogen in the roots of S. patens. P. australis within sites had wide ranges of delta (15)N values, evidently influenced by the type of shoreline development or buffer at the upland border. In residential areas, the presence of a vegetated buffer (n = 24 locations) significantly (P < 0.001) reduced the delta (15)N (mean = 7.4 +/- 0.43 per thousand) of the P. australis compared to stands where there was no buffer (mean = 10.9 +/- 1.0 per thousand; n = 15). Among the plant species, I. frutescens located near the upland border showed the most significant (R (2) = 0.64; P = 0.006) inverse relationship with the percent agricultural land in the watershed. The delta (15)N of P. australis and I. frustescens is apparently an indicator of local inputs near the upland border, while the delta (15)N of Spartina relates with the integrated, watershed-sea nitrogen inputs.

Ecosystem↗
PubMed2006

Palatability of macroalgae that use different types of chemical defenses.

This study compared algal palatability and chemical defenses from subtropical green algae that may use different types of defense systems that deter feeding by the rock-boring sea urchin Echinometra lucunter. The potential defense systems present include (1) the terpenoid caulerpenyne and its activated products from Caulerpa spp., and (2) dimethylsulfoniopropionate (DMSP)-related defenses in Ulva spp. Secondary metabolites from these chemical groups have been shown to deter feeding by various marine herbivores, including tropical and temperate sea urchins. Live algal multiple-choice feeding assays and assays incorporating algal extracts or isolated metabolites into an artificial diet were conducted. Several green algae, including Ulva lactuca, Caulerpa prolifera, and Cladophora sp., were unpalatable. Nonpolar extracts from U. lactuca deterred feeding, whereas nonpolar extracts from C. prolifera had no effect on feeding. Polar extracts from both species stimulated feeding. Caulerpenyne deterred feeding at approximately 4% dry mass; however, dimethyl sulfide and acrylic acid had no effect at natural and elevated concentrations. E. lucunter is more tolerant than other sea urchins to DMSP-related defenses and less tolerant to caulerpenyne than many reef fish. Understanding the chemical defenses of the algae tested in this study is important because they, and related species, frequently are invasive or form blooms, and can significantly modify marine ecosystems.

Animals↗
PubMed1990

Biochemical characterization of algal coated vesicles.

Thin sections of tissue preparations from a green alga, Ulva lactuca (Ulvophyceae), and brown alga, Laminaria digitata (Pheophyceae) showed the presence of coated pits and coated vesicles in these 2 species. A discontinuous sucrose gradient after subcellular fractionation of the tissue homogenate resulted in an enriched coated vesicle fraction. Electron microscopy of negatively stained samples revealed the presence of coated vesicles of diameter ranging from 40-125 nm, together with large sheets of polygonal nets of clathrin. Electrophoresis of the CV purified fraction revealed various polypeptide components. Two of them, a 175 kDa and a 70 kDa, exhibited a positive response to bovine brain anticlathrin antibodies raised in goat or in rabbit. A third component of 30-40 kDa also gave a faint positive response. These 3 components corresponded to the clathrin heavy and light chains already described in higher plants. Clathrin was released from the CV algal preparations by treatment with 2M urea in Tris buffer, pH 8.5. Interestingly, in Ulva lactuca, the proportion of clathrin relative to the other proteins from the CV decreased with plant growth. Biochemical analysis of the purified CV revealed the presence of all the major phospholipids characterized in mammalian CV. The ratio of protein over lipid was also in the same range as that calculated for mammalian CV. Carbohydrate analysis demonstrated a high proportion of N-acetylgalactosamine and N-acetylglucosamine in both algal CV whereas these sugars were not detectable in the crude homogenate. These results demonstrate the presence of clathrin and coated vesicles in 2 species of algae.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

The impact of a macroalgal mat on benthic biodiversity in Poole Harbour.

Blooms of macroalgal matting are increasingly common within temperate zones and are often comprised of opportunistic species such as Ulva lactuca. Where this algae forms a dense mat, a stressful environment is created in the sediment below, influencing the invertebrate infaunal assemblage. This study was conducted over a six month period during which a dense mat of U. lactuca developed and subsequently dispersed. The algal mat was found to have a significant negative impact on species richness, abundance and biomass of the macroinfauna. However, a faunal community developed within the algal mat which contained several species not previously observed. This community increased the abundance and diversity of the overall invertebrate assemblage. The results are discussed in relation to impacts on the ecosystem as a whole.

Analysis of Variance↗
PubMed2005

Nitrogen isotope ratios in estuarine biota collected along a nutrient gradient in Narragansett Bay, Rhode Island, USA.

Stable nitrogen isotope ratios were used to study the incorporation of anthropogenically-derived nitrogen into the food webs of salt marsh systems along a contamination gradient in Narragansett Bay. Nitrogen isotope ratios (delta(15)N) were measured in six estuarine species collected from three marshes along this gradient, monthly from June to October between 1997 and 1999. A significant decrease in delta(15)N was found with distance along the estuary for four of the six species. Significant differences were found among monthly isotope ratios for some species. Nitrogen isotope ratios in sea lettuce (Ulva lactuca) increased during the summer season with highest delta(15)N values measured during September and October. This trend was most pronounced at the station receiving the highest nutrient inputs. Elevated delta(15)N values at this station appeared to correlate with seawater ammonia/nitrate concentration ratios. The temporal variations in delta(15)N suggest that care should be taken in species selection and the design of sampling schemes of studies using delta(15)N for monitoring anthropogenic nutrients in aquatic systems. Sampling programs designed to determine long-term trends should consider species that do not show rapid fluctuations in isotope ratios. The mud snail, Nassarius obsoletus, responded this way in the present study. Studies designed to measure short-term changes should include species such as U. lactuca, which rapidly respond to isotope changes. The results from this study also help to establish a baseline for nitrogen isotope values in Narragansett Bay. This information can be used to monitor future trends in nitrogen inputs to this estuary.

Animals↗
PubMed2006

PCR-identification of Dunaliella salina (Volvocales, Chlorophyta) and its growth characteristics.

The saline pond microalga, Dunaliella salina (Dunal) Teod. maintained in De Walne's (basal) medium under laboratory conditions was confirmed by amplifying the chromosomal DNA of the microalga by PCR with specific primers MA1 and MA2. Seaweed extracts obtained from Sargassum wightii and Ulva lactuca were amended separately at 1.0%, 1.5%, 2.0% and 2.5% levels to the basal medium in order to assess their potential on the growth and concentration of pigments, viz. Chl a, Chl b and beta-carotene of the alga. beta-Carotene was isolated and visible absorption spectrum was taken at 443 and 475 nm confirmed the presence of 9-cis-beta-carotene and all-trans-beta-carotene isomers. Maximum yield, highest division rate (mu) and highest pigment concentrations were observed in the cells grown in 1.5% S. wightii and 2.0% U. lactuca amended medium and these cells were subjected to DAPI staining. The results of epifluorescence microscopy and image analysis revealed a significant enhancement of the cell and nuclear area of the microalgae.

Chlorophyll↗
PubMed2004

Phylogenetic relationships of Plasmopara, Bremia and other genera of downy mildew pathogens with pyriform haustoria based on Bayesian analysis of partial LSU rDNA sequence data.

Bayesian and maximum parsimony phylogenetic analyses of 92 collections of the genera Basidiophora, Bremia, Paraperonospora, Phytophthora and Plasmopara were performed using nuclear large subunit ribosomal DNA sequences containing the D1 and D2 regions. In the Bayesian tree, two main clades were apparent: one clade containing Plasmopara pygmaea s. lat., Pl. sphaerosperma, Basidiophora, Bremia and Paraperonospora, and a clade containing all other Plasmopara species. Plasmopara is shown to be polyphyletic, and Pl. sphaerosperma is transferred to a new genus, Protobremia, for which also the oospore characteristics are described. Within the core Plasmopara clade, all collections originating from the same host family except from Asteraceae and Geraniaceae formed monophyletic clades; however, higher-level phylogenetic relationships lack significant branch support. A sister group relationship of Pl. sphaerosperma with Bremia lactucae is highly supported. Within Bremia lactucae s. l., three distinct clades are evident, which only partly conform to the published host specificity groups. All species of the genera Basidiophora, Bremia, Paraperonospora and Plasmopara included in the present study were investigated for haustorial morphology, and all had ellipsoid to pyriform haustoria, which are regarded as a diagnostic synapomorphy of the whole clade. Aspects of coevolution and cospeciation within the downy mildew pathogens with ellipsoid to pyriform haustoria are briefly discussed.

Bayes Theorem↗
PubMed2003

The development of a marine natural product-based antifouling paint.

Problems with tin and copper antifouling compounds have highlighted the need to develop new environmentally friendly antifouling coatings. Bacteria isolated from living surfaces in the marine environment are a promising source of natural antifouling compounds. Four isolates were used to produce extracts that were formulated into ten water-based paints. All but one of the paints showed activity against a test panel of fouling bacteria. Five of the paints were further tested for their ability to inhibit the settlement of barnacle larvae, Balanus amphitrite, and algal spores of Ulva lactuca, and for their ability to inhibit the growth of U. lactuca. Two paints caused a significant decrease in the number of settled barnacles. One paint containing extract of Pseudomonas sp. strain NUDMB50-11, showed excellent activity in all assays. The antifouling chemicals responsible for the activity of the extract were isolated, using bioassay guided fractionation, and their chemical structures determined.

Animals↗