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  • 1
    Electronic Resource
    Electronic Resource
    Traveling bands of chemotactic bacteria in the context of population growth (1984)
    Springer
    Bulletin of mathematical biology 46 (1984), S. 19-40 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A mathematical model for traveling bands of motile and chemotactic bacteria in the presence of cell growth and death is examined. It is found that asymptotic traveling wave solutions exist in the absence of chemotaxis, due to the balance of growth, death and random motility. Thus random motility confers the ecological advantage of population propagation through migration into nutrient-rich regions. The presence of chemotaxis amplifies this advantage by moving more cells into higher nutrient concentration regions, resulting in larger and faster bands. Therefore there seem to be two types of traveling bands that can be attained by chemotactic bacteria in the presence of growth and death: (1) these growth/death/motility bands; and (2) pure chemotactic ‘Keller-Segel'-type bands. Comparison to experimental observations by Chapman in 1973 indicate that the latter seem to be formed. The relationship between these two types of solution is at present uncertain. The growth/death/motility bands may have relevance on longer time or distance scales characteristic of microbial ecological systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02463721
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  • 2
    Electronic Resource
    Electronic Resource
    Traveling waves in a simple population model involving growth and death (1980)
    Springer
    Bulletin of mathematical biology 42 (1980), S. 397-429 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The structure of solutions to a simple spatially dependent population model involving growth and death is investigated. Two forms of motility of the population are considered: (1) random motion only modeled by a Fickian law, and (2) a directed component of motion (chemotaxis), included in addition to the random motion. Under certain growth conditions a traveling wave of constant speed is approached. This speed can be increased by the addition of the chemotaxis with a corresponding increase in the asymptotic population. Development of initial conditions into a wave is illustrated numerically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02460793
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  • 3
    Electronic Resource
    Electronic Resource
    Benzo[a]pyrene Toxicokinetics in Rainbow Trout (Oncorhynchus mykiss) Acclimated to Different Salinities (2000)
    Springer
    Archives of environmental contamination and toxicology 38 (2000), S. 342-349 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The effects of environmental salinity on the distribution, metabolism, and elimination of benzo[a]pyrene (B[a]P) were examined in mature rainbow trout. Trout acclimated to either fresh water (0 ppt, FW) or sea water (20 ppt, SW) for 3 weeks received a single 10 mg/kg intra-arterial injection of [3H]-benzo[a]pyrene (B[a]P) at their acclimation salinity or when subjected to an acute salinity change. Statistically significant differences in the percent body burden of B[a]P-derived radioactivity in various tissues were seen between fish in FW versus SW. Significant differences in the distribution of B[a]P and its metabolites were also noted when fish were subjected to an acute salinity change after chemical injection. Modulation of B[a]P metabolism by environmental salinity included: (1) significant differences in the proportions of Phase I metabolites in the bile of FW- (2.3%) versus SW-acclimated (14.1%) fish, and (2) alterations in the accumulations of specific metabolites (predominantly t-9, 10-dihydrodiol-B[a]P in FW fish, and 3-hydroxy-B[a]P in SW fish). The percentages of the [3H]-B[a]P dose eliminated by 48 h was similar in FW and SW fish, but decreased in fish subjected to an acute salinity change (FW 98.8% eliminated, FW:SW 90.4%, SW 98.1%, and SW:FW 93.1%). Pharmacokinetic modeling confirmed that acute salinity changes can result in longer terminal half-lives and slower total body clearances of B[a]P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449910045
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  • 4
    Electronic Resource
    Electronic Resource
    The Effect of Bioaccumulated Selenium on Mortalities and Deformities in the Eggs, Larvae, and Fry of a Wild Population of Cutthroat Trout (Oncorhynchus clarki lewisi) (2000)
    Springer
    Archives of environmental contamination and toxicology 39 (2000), S. 46-52 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract To determine if elevated concentrations of waterborne selenium (Se), caused by coal mining, in the Elk River in southeastern British Columbia, may be causing reproductive or teratogenic effects in wild cutthroat trout (Oncorhynchus clarki lewisi), fertilized eggs from exposed and reference fish were raised in the laboratory. Eggs from each female were reared separately and the percent mortalities and deformities were related to the selenium content of the eggs. Selenium concentrations in females from the exposed site were highest in the liver (36.6 ± 22.5 μg/g dry weight, range: 18.3 to 114), followed by the eggs (21.0 ± 18.3 μg/g, range: 8.7 to 81.3) and the muscle (12.5 ± 7.7 μg/g, range: 6.7 to 41). Despite these elevated egg Se concentrations, there was no significant effect on fertilization; time to hatch; percent hatch; or egg, larvae, and fry deformities or mortalities. Reproductive failure and embryonic terata have been reported at much lower egg Se concentrations in other fish species. The lack of any toxic response in this study may be due to an evolved tolerance to higher tissue Se concentrations in a population of fish living in a seleniferous river system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002440010078
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  • 5
    Electronic Resource
    Electronic Resource
    Biochemical Effects of Didecyldimethylammonium Chloride (DDAC) Exposure and Osmoregulatory Stress on Juvenile Coho Salmon, Oncorhynchus kisutch (1998)
    Springer
    Archives of environmental contamination and toxicology 34 (1998), S. 275-279 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The effects of a seawater challenge on coho salmon, Oncorhynchus kisutch, previously exposed to didecyldimethylammonium chloride (DDAC) were examined. In one experiment, salmon were exposed to three sublethal concentrations of DDAC over three durations followed by a 24-h seawater challenge in a computer-controlled, intermittent-flow respirometer to measure effects on several biochemical variables. After a 144-h dose, plasma cortisol, glucose, and gill Na+/K+-ATPase activity were significantly increased at a nominal DDAC concentration of 0.2 mg/L. In the second experiment, animals were exposed to five different concentrations for 24 h followed by a 24-h seawater challenge. Plasma cortisol was significantly increased at the highest exposure concentration (0.75 mg/L). Plasma Na+ was significantly elevated at exposure concentrations of 0.3, 0.5, 0.65, and 0.75 mg/L. Gill Na+/K+-ATPase activity was significantly reduced at exposure concentrations of 0.65 mg/L and 0.75 mg/L. The use of the seawater challenge to demonstrate sublethal physiological stress and impaired osmoregulatory capacity in coho salmon smolts is relevant to salmonid life history in terms of the animal's transition from freshwater to seawater during its seaward migration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449900318
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  • 6
    Electronic Resource
    Electronic Resource
    A Study of the Lethal and Sublethal Toxicity of Polyphase P-100, an Antisapstain Fungicide Containing 3-Iodo-2-Propynyl Butyl Carbamate (IPBC), on Fish and Aquatic Invertebrates (2000)
    Springer
    Archives of environmental contamination and toxicology 38 (2000), S. 260-261 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449910034
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  • 7
    Electronic Resource
    Electronic Resource
    Patch-size dependent habitat modification and facilitation on New England cobble beaches by Spartina alterniflora (2000)
    Springer
    Oecologia 122 (2000), S. 98-108 
    Details
    ISSN: 1432-1939
    Keywords: Key words Cobble beach ; Facilitation ; Flow velocity ; Habitat modification ; Spartina alterniflora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Most marine habitats are generated by the presence of habitat-modifying species. However, little is know about many aspects of this process, such as how individual- and population-level traits of habitat modifiers affect their ability to reduce environmental stress and thus facilitate other species. An important habitat modifier in New England is the intertidal grass Spartina alterniflora which facilitates the establishment and persistence of cobble beach plant communities by reducing wave-related disturbance. The objectives of this study were to (1) quantify the modification of cobble beach habitats by S. alterniflora, (2) determine how this process is related to S. alterniflora bed traits, and (3) determine why small patches of S. alterniflora generally remain unoccupied by cobble beach plants. Our results demonstrate that S. alterniflora substantially reduces flow-related physical disturbance on cobble beaches. Behind S. alterniflora, mean flow velocity was reduced by 40–60% and substrate stability was dramatically increased compared to portions of the shoreline not bordered by this species. These comparative results were supported by a S. alterniflora shoot removal experiment, which resulted in a 33% increase in average flow velocity and an 85% increase in substrate instability relative to control areas. There was a strong inverse logarithmic relationship between bed length and both average flow velocity and substrate instability behind S. alterniflora. Most S. alterniflora beds were small and bed length was significantly related to the presence of one or more cobble beach plant species. Only 13% of beds 〈25 m and 40% of beds 30–40 m in length were occupied, in contrast to an occupancy rate of 87% for beds 〉40 m long. Seeds of two annual cobble beach species (Suaeda linearis and Salicornia europaea) were added to plots behind large (〉100 m in length) and small S. alterniflora (〈25 m) beds with and without a substrate stabilization manipulation. Seedlings of both species only emerged and established behind small beds when the substrate was stabilized. These results indicate that smaller S. alterniflora patches are usually unoccupied because they do not stabilize the substrate to a degree that meets the establishment requirements of seedlings. Thus, both habitat modification and facilitation by S. alterniflora are patch-size dependent. The conditionality of this facilitation appears to generate a pattern of patchy yet predictable population and community distribution at a landscape spatial scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008841
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  • 8
    Electronic Resource
    Electronic Resource
    A Study of the Lethal and Sublethal Toxicity of Polyphase P-100, an Antisapstain Fungicide Containing 3-Iodo-2-Propynyl Butyl Carbamate (IPBC), on Fish and Aquatic Invertebrates (1998)
    Springer
    Archives of environmental contamination and toxicology 35 (1998), S. 472-478 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The acute toxicity of Polyphase P-100, an antisapstain wood preservative that contains 97% 3-iodo-2-propynyl butyl carbamate (IPBC), was determined for three species of fish (coho salmon, rainbow trout, and starry flounder) and three species of aquatic invertebrates (Daphnia magna, Hyalella azteca, and Neomysis mercedis). The 96-h LC50 values for the various fish species exposed to Polyphase P-100 ranged from 95 ppb for coho smolts (Oncorhynchus kisutch) to 370 ppm for juvenile starry flounder (Platichthys stellatus). The sensitivity of coho to Polyphase P-100 was altered by their developmental stage. Coho embryos were six to nine times more tolerant of Polyphase P-100 than coho alevins, which were twice as tolerant as coho smolts. The 48-h LC50 values for the invertebrates D. magna, H. azteca, and N. mercedis were 40 ppb, 500 ppb, and 2,920 ppb, respectively. In addition to a wider range of sensitivity to Polyphase P-100 compared with the fish species, the invertebrate species were characterized by a shallower concentration-response. In acute, 24-h sublethal tests with juvenile starry flounder and rainbow trout, there was no primary or secondary stress response (changes in hematocrit, leucocrit, hemoglobin concentration, plasma lactate concentration, and plasma cortisol concentration) at concentrations up to 50% of the 96-h LC50 value. The acute toxicity of a 1:8 mixture of Polyphase P-100 and Bardac 2280 (another antisapstain compound that contains didecyldimethylammonium chloride [DDAC] as the active ingredient) was close to additive for fish, but not for invertebrate species. The acute toxicity of the mixture was seven to eight times more than additive for H. azteca, but two to three times less than additive for D. magna. Some sublethal stress responses were revealed with the mixture that were not observed with the test chemicals alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449900404
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  • 9
    Electronic Resource
    Electronic Resource
    The fate of benzo[a]pyrene in the scleractinian corals Favia fragum and Montastrea annularis (1992)
    Springer
    Marine biology 113 (1992), S. 313-318 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fate of the polycyclic aromatic hydrocarbon [3H]benzo[a]pyrene (BaP) was examined in two species of scleractinian corals, Favia fragum (Esper) and Montastrea annularis (Ellis and Solander), which were collected in the patch reefs surrounding Alina's Reef (25°23.25′N; 80°09.8′W) in Biscayne National Park, Florida, USA, in July, 1990. Corals were exposed to initial concentrations of 5 μg/l in a simple static system for 25 h. BaP uptake was estimated from the disappearance of BaP from the water. Uptake rates were 6.5±0.7 and 10.8±0.2 μg BaP cm-2h-1 for F. fragum and M. annularis, respectively, at initial BaP concentrations and were directly proportional to the concentration of BaP in the water. The separation of zooxanthellae from coral tissue revealed that zooxanthellae can accumulate up to 53 and 64% of the total BaP-derived radioactivity present in F. fragum and M. annularis, respectively. Both corals metabolized BaP slowly, as most of the accumulated radioactivity was present as the unmetabolized chemical. However, aqueous and organic-soluble metabolites were found in both the animal and zooxanthellae fractions. Analysis by high-performance liquid chromatography (HPLC) revealed that both species of corals metabolized BaP to various tetrols, triols, dihydrodiols, quinones and phenols, although the pattern of metabolites differed between species. Zooxanthellae contained some of the same Phase I metabolites found in the animal tissue; however, tetrols and triols were absent in extracts from the zooxanthellae. The elimination of BAP from corals was also slow; approximately 38 and 65% of the accumulated radioactivity was still present in F. fragum and M. annularis, respectively, 144 h following the transfer of exposed corals to an uncontaminated flow-through seawater system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00347286
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  • 10
    Electronic Resource
    Electronic Resource
    The role of regulatory genes nifA, vnfA, anfA, nfrX, ntrC, and rpoN in expression of genes encoding the three nitrogenases of Azotobacter vinelandii (1994)
    Springer
    Archives of microbiology 162 (1994), S. 422-429 
    Details
    ISSN: 1432-072X
    Keywords: Key words     Nitrogen fixation ; Vanadium ; anf ; Azotobacter ; nif ; Sigma(σ)54 ; Sigma(σ)N ; Molybdenum ; vnf ; ntrC ; rpoN
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract      Several regulatory gene mutants of Azotobacter vinelandii were tested for ability to synthesize functional nitrogenase-1 (Nif phenotype), nitrogenase-2 (Vnf), or nitrogenase-3 (Anf). While nifA mutants were Nif–, Vnf+, and Anf+/–, and ntrC mutants were Nif+, Vnf+, and Anf+, nifA ntrC double mutants were Nif–, Vnf–, and Anf–. A vnfA mutant was Nif+, Vnf+\–, and Anf+\–, and an anfA strain was Nif+, Vnf+, and Anf–. lacZ fusions in the nifH, vnfH, vnfD, anfH, and nifM genes of Azotobacter vinelandii were constructed and introduced into wild-type and regulatory mutants of A. vinelandii. Expression of these operons correlated with the growth phenotype of the regulatory mutants. Apparently either NifA or NtrC can activate expression of nifM. Also, expression of the anf operon required the NifA transcriptional activator, although there are no NifA binding sites at appropriate locations upstream of anfH (or anfA). The results confirm previous reports that VnfA and AnfA are required for expression of vnf and anf genes, respectively, and that VnfA is involved in repression of the nifHDK operon in the absence of molybdenum and of the anfHDGK operon in the presence of vanadium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050160
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