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  • 1
    Electronic Resource
    Electronic Resource
    Sediment Toxicity Bioassays for Assessment of Contaminated Sites in the Nervion River (Northern Spain). 2. Tubifex tubifex Reproduction Sediment Bioassay (1999)
    Springer
    Ecotoxicology 8 (1999), S. 111-124 
    Details
    ISSN: 1573-3017
    Keywords: Tubifex tubifex ; sediment bioassay ; hormesis ; growth ; reproduction ; egestion rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Toxicity assessment based on sediment chronic bioassays with the aquatic worm Tubifex tubifex was performed at ten contaminated sites in the industrial area of Bilbao (Northern Spain). One control and three reference sites were also included. Tubifex bioassay measures both survival and reproduction impairment. These endpoints have been contrasted and discussed in relation to somatic growth and both individual and total biomass of cocoons. Survival was only affected at one site which was heavily contaminated by organic compounds, mainly PAHs. A group of four severely ecotoxic sediments was characterised by a drastic reduction in number and size of cocoons, and adult somatic growth. In other group of sediments, some significant increases were found for these variables. It is suggested that these increases represent an effect of hormesis. An index of reproductive effort was used to integrate the relationship between somatic growth and reproduction. Values of reproductive effort at the test sediments were lower than those at the control sediment, suggesting a conservative strategy of oligochaete worms which consisted in an investment into somatic line (growth) at the expenses of offspring. Rates of food consumption which were estimated from egestion rates, were low at the contaminated sites. This fact could be related to the low production levels found at these sites and may reflect avoidance feeding behaviour of the oligochaete worms within the sediments. At some reference sites, high production could have resulted from high nutritional quality of sediments, or to an hormetic effect due to low concentration of some chemicals. Results are discussed in relation to toxicity data from sediment three-brood bioassay with Daphnia magna Straus performed separately on the same sediments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008966702822
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of salinity and pH on growth and agar yield of Gracilaria tenuistipitata var. liui in laboratory and outdoor cultivation (1999)
    Springer
    Journal of applied phycology 11 (1999), S. 543-549 
    Details
    ISSN: 1573-5176
    Keywords: agar ; Gracilaria tenuistipitata ; growth ; salinity ; seawater pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acclimation responses of the red alga Gracilaria tenuistipitata var. liui collected on the northwest coast of Philippines were determined in laboratory setups and outdoor cultivation tanks in Haifa, Israel. Growth under laboratory conditions was influenced by all three variables studied, namely, temperature (20 or 30 °C), salinity (20, 30 or39‰) and seawater pH (6.5, 7.0, 8.0 or ≥ 9.0). In 250 mL flasks lacking pH control growth was influenced by temperature only at 20 ‰, whereas at 39 ‰, growth rates were similar at 20 or 30 °C. In 500 mL cylinders in which pH was controlled, growth rates were significantly different at a pH of 6.5 and 7.0 for all salinities, with maximal rates occurring in 39 ‰. At pH 8.0, and above, growth rates between salinities were similar and reduced to approximately 50% at a pH of 9.0 compared to rates at a pH of 6.5. Photosynthesis responses generally resembled growth responses both, in 250 mL and 500 mL cultures. In 40-L outdoor tanks, weekly growth and agar yields were apparently enhanced by increasing light intensities (up to full sunlight) and nutrient concentrations (up to 0.2 mM PO3 2- and 2.0 mM NH4 +), and rates averaged four times higher than rates determined in the smaller flask cultures. This study shows broad salinity tolerance of G. tenuistipitata var. liui and its ability to sustain growth rates that are among the highest measured for Gracilaria spp. in outdoor cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008141906299
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  • 3
    Electronic Resource
    Electronic Resource
    Food dependent color patterns inThamnocephalus platyurus Packard (Branchiopoda: Anostraca); a laboratory study (1995)
    Springer
    Hydrobiologia 298 (1995), S. 133-139 
    Details
    ISSN: 1573-5117
    Keywords: β-carotene ; baker's yeast ; growth ; survival
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Coloration of phyllopods varies from place to place and from one life stage to another. It ranges from translucent or whitish through gray, blue, green, orange, and reddish. Here, we present experimental evidence for a food- dependent color pattern inThamnocephalus platyurus Packard. The presence or absence of the synthetic pigment trans — β — carotene in a baker's yeast diet was the controlling factor. All the 24 old larvae used in the experiment were whitish in color. From day 6 until the end the experiment (day 11), 100% of the shrimps under a diet with synthetic trans — β — carotene (treatment 1) exhibited a characteristic color pattern which consisted of an orange color in the cercopods, and in all theracopods; the rest of the body exhibited no particular color. In comparison, 100% of the shrimps under a diet without synthetic trans — β — carotene (treatment 2) were whitish throughout the body. In females from treatment 1, the ovaries and oocytes were green-bluish, while in females from treatment 2 the ovaries and oocytes were whitish. No significant differences in survival and growth were found, except that at day 9, there was a significant difference in growth, the females with the synthetic trans — β — carotene group growing faster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033808
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  • 4
    Electronic Resource
    Electronic Resource
    Laboratory culture of fairy shirmps using baker's yeast as basic food in a flow-through system (1995)
    Springer
    Hydrobiologia 298 (1995), S. 141-157 
    Details
    ISSN: 1573-5117
    Keywords: Thamnocephalus ; Branchinecta ; growth ; filter-feeders ; feeding ; clay ; silicium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We designed and standardized a culture method for freshwater anostracans using diets free of live algae.Thamnocephalus platyurus andBranchinecta lindahli were used as test organisms. We used baker's yeast as basic food and added inert particles (clay or amorphic silicium dioxide) to improve the digestion of the yeast. A flow-through culture system was used, according to a fixed feeding schedule, to supply separately, culture medium (tap water), food, and inert particle suspensions. Three variants with baker's yeast as basic, food were compared for survival, growth, and reproduction. A diet of solely baker's yeast (diet 1) or baker's yeast supplemented with vegetal oil containing ß-carotene (diet 2) was unsuitable for reproduction ofT. platyurus. Cyst production was only achieved when diet 2 was supplemented with fish oil andSpirulina powder (diet 3). This suggests that not only a digestibility problem, but also nutritional deficiencies are present in baker's yeast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033809
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  • 5
    Electronic Resource
    Electronic Resource
    A comparison of reproduction, growth and acute toxicity in two populations of Tubifex tubifex (Müller,1774) from the North American Great Lakes and Northern Spain (1996)
    Springer
    Hydrobiologia 334 (1996), S. 199-206 
    Details
    ISSN: 1573-5117
    Keywords: toxicity ; cultures ; oligochaetes ; T. tubifex ; growth ; reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproduction in Tubifex tubifex is being used as part of a suite of indicators of sediment toxicity in Canada and Spain, and reproduction of T. tubifex is being considered as a component of sediment objectives for environmental regulation and clean-up in the Canadian Great Lakes. The data being used to set these reproductive targets have been developed from a single culture of T. tubifex from Lake Erie. The plasticity of this particular species is well known and before it can be adopted widely as a test organism it is necessary to determine whether a single culture source should be used or if cultures derived from different populations respond similarly. A series of experiments with two cultures, one from Lake Erie the second from a small mountain stream in Northern Spain have shown that the Spanish worms appear to produce fewer cocoons per adult (mean 8.6 S.D. 1.0) than those from Lake Erie (mean 10.4 S.D. 0.3) at 22.5 °C, a standard test temperature. The number of young produced per adult by the Spanish culture is also lower (mean 19.0 S.D. 4.6) than the L. Erie population (mean 30.6 S.D. 2.3), however, the Spanish population has higher reproductions rates at a lower temperature. The Spanish worms also have lower and more variable growth rates than the Canadian population. There also appear to be slight differences in the sensitivities to toxicants, with the Canadian worms having higher LC50s for copper, chromium and cadmium. While there are differences in the responses in the two cultures these are not considered to be sufficient to invalidate the use of either population in a standard bioassay protocol as long as appropriate calibration and validation are undertaken.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017370
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  • 6
    Electronic Resource
    Electronic Resource
    Indentification of Acetobacter diazotrophicus, Herbaspirillum seropedicae and Herbaspirillum rubrisubalbicans using biochemical and genetic criteria (1995)
    Springer
    Plant and soil 172 (1995), S. 271-277 
    Details
    ISSN: 1573-5036
    Keywords: Acetobacter ; Herbaspirillum ; growth ; identification ; PCR ; sugarcane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrogen-fixing Acetobacter diazotrophicus, Herbaspirillum seropedicae and Herbaspirillum rubrisubalbicans colonize sugar cane, and are thought to be capable of supplying high levels of fixed nitrogen to this plant. Eight A. diazotrophicus, two H. seropedicae and four H. rubrisubalbicans isolates were identified and compared by complementary biochemical and genetic methods. Utilization of carbon sources and antibiotic resistance patterns allowed differentiation of A. diazotrophicus from Herbaspirillum species. In order to distinguish strains within A. diazotrophicus species, the polymerase chain reaction was employed, using a Rhizobium meliloti dctA primer under low stringency hybridization conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011329
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  • 7
    Electronic Resource
    Electronic Resource
    Fracture of DNA in transient extensional flow. A numerical simulation study (1996)
    New York : Wiley-Blackwell
    Biopolymers 39 (1996), S. 435-444 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the Brownian dynamics simulation technique, we studied the fracture process of DNA chains subjected to transient extensional flow, letting the solution with DNA molecules pass through a very small orifice (radius = 0.0065 cm), thus experiencing extensional flow of the convergent (sink) type. The DNA molecules were modeled as FENE bead-spring chains with the springs obeying a modified Warner force law, as proposed by Reese and Zimm. The fracture yield was strongly dependent on flow rate and molecular weight, reaching, in our setup, a level of 100% at a flow rate of around 0.001 cm3/s for DNA with molecular weight 26 × 106 (T7 DNA). There was found to exist a critical flow rate (Qcrit) below which fracture did not occur, in accordance with what was observed in studies on polystyrene in transient extensional flow. We found that for DNA, the critical flow rate depended on the molecular weight as Qcrit ∼ M-14 when the hydrodynamic interaction effect (HI) was not included in the simulations. When HI was accounted for, the relation was found to be Qcrit ∼ M-1.1, close to the theoretical prediction for fracture of partly extended chains in transient extensional flow. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Conformationally readdressed CCK-B/δ-opioid pepitide ligands (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 439-452 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sequence of a cholecystokinin (CCK) related peptide was modified to obtain analogues, which intereact selectively either with CCK-B, or with δ-opioid receptors. Two kinds of peptides were designed, namely, the cyclic peptides of the H-Tyr-cyclo(D-Pen-Gly-Trp-L-/D-3-transmecaptoproline)-Asp-Phe-NH2 sequence (compounds 1a and 1b, respectively), and the linear peptides of the H-Tyr-D-Val-Gly-Trp-L/D-3-trans-methylmercaptoproline-Asp-Phe-NH2 sequence (compounds 2a and 2b, respectively). The only difference between the chemical structures of the linear analogues compared to the cyclic ones is that one covalent bond has been eliminated and a sulfur atom is replaced by a methyl group. Molecular modeling showed that, among low-energy conformers of cyclic compounds 1, there are three-dimensional structures compatible to the model for δ- receptor- bound conformer, suggested earlier[G. V. Nikiforovich. V. J. Hruby. O. Prakash, and C. A. Gehrig (1991) Biopolymers. vol. 31. pp. 941-955]. Results of binding assays fully supported the rationale for the design of compounds 1 and 2. The cyclic analogue 1a has Ki values of 4.5 and 〉 5000 n M at δ- and μ-opioid receptors, respectively; IC50 values of 3000 n M for both CCK-A and CCK-B receptors, whereas its linear counterpart 2a has ki values of 462 and 229 nM at δ- and μ-opioid receptors, respectively; and IC50 values of 1.6 and 〉 10.000 nM for CCK-A and CCK-B receptors, respectively. The results of this study demonstrate a possibility to redirect a peptide sequence that interacts with one type of receptors (CCK-B receptors) toward interaction with another type (δ-opioid receptors) belonging to a different physiological system. This redirection could be performed by changing the conformational properties of the peptide with very minimal changes in its chemical structure. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360360407
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  • 9
    Electronic Resource
    Electronic Resource
    Poly(α-isobutyl-β-D,L-aspartate)s: Polymerization effects on configuration and crystal structure of the stereocopolymers (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1959-1968 
    Details
    ISSN: 0887-624X
    Keywords: optically active polyamides ; helical nylons ; nylon-3 ; poly(β-amide)s ; poly(β-aspartate)s ; poly(α-isobutyl-β-L-aspartate) ; stereoselective polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Different polymerization methods were used for the preparation of poly(α-isobutyl-β-D,L-aspartate)s containing variable ratios of D- to L-aspartic units and the microstructure of the resulting stereocopolymers was examined by NMR spectroscopy. Anionic ring-opening polymerization in solution of enantiomeric mixtures of α-isobutyl-β-D- and L-aspartalactams was found to proceed stereoselectively rendering block copolymers composed of right- and left-handed helical sequences. Configurationally statistical copolymers were obtained instead when the enantiomeric lactam mixtures were polymerized in the bulk. Random stereocopolymers could be prepared also by polycondensation in solution of mixtures of pentachlorophenyl α-isobutyl-β-D and -L-aspartates. The conformation in solution and the crystal structure of the resulting copolymers were investigated in connection with their stereochemical configuration and these features compared with those displayed by optically pure poly(α-isobutyl-β-L-aspartate). © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Local chain configuration dependence of the mechanisms of analogous reactions of PVC. I. A conclusive study of the microstructure evolution in SN2 nucleophilic substitution (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2387-2397 
    Details
    ISSN: 0887-624X
    Keywords: poly(vinyl chloride) ; nucleophilic substitution ; stereospecific mechanisms ; solvent influence ; microstructural sensitivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nucleophilic substitution in poly(vinyl chloride) (PVC) with sodium benzenethiolate has been studied in two kinds of solvent differing in the molecular structure in the vicinity of the carbonyl group. From the evolution of the content of isotactic (mm), heterotactic (mr), and syndiotactic (rr) triads; and of mmmm, mmmr and rmmr isotactic pentads, in the unmodified parts of the polymer, as followed by 13C-NMR, it is unambiguously inferred that any chlorine but the central one of either the isotactic triad at mmr tetrads or the heterotactic triad at rmrr pentads is unreactive. Only a small fraction of mmr tetrads reacts occasionally by the central chlorine of its mr triad instead of the mm. Of those structures, the mmr, especially when located at the end of long isotactic sequences, proves to be highly reactive compared to the rmrr structure. By comparing quantitatively the microstructural changes with degree of substitution and taking into account that the reaction is of SN2 type, the mechanisms of substitution through the three foregoing reactive chlorines have been stated. They are found to be independent of the type of solvent and to account for all the changes in triad and pentad content as experimentally found. Instead, the solvent dependence of the ratio between the mmr- and rmrr-based processes of substitution is such that the depletion of mmr compared to that of rmrr structure may be controlled. The conformational sensitivity of this behavior is discussed on the basis of side work in our laboratory. As a whole, the results of the present work provide some original concepts as to the role of the tacticity dependent microstructure and the related local conformations in the chemical reactions of PVC. © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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