bluuebunny/crossref_metadata_2025 huggingface dataset:
Transcription Activation by NtcA and 2-Oxoglutarate of Three Genes Involved in Heterocyst Differentiation in the Cyanobacterium
Anabaena
sp. Strain PCC 7120
Authors: Valladares Ana , Flores Enrique , Herrero Antonia
Published: July 2008

In
Anabaena
sp. strain PCC 7120, differentiation of heterocysts takes place in response to the external cue of combined nitrogen deprivation, allowing the organism to fix atmospheric nitrogen in oxic environments. NtcA, a global transcriptional regulator of cyanobacteria, is required for activation of the expression of multiple genes involved in heterocyst differentiation, including key regulators that are specific to the process. We have set up a fully defined in vitro system, which includes the purified
Anabaena
RNA polymerase, and have studied the effects of NtcA and its signaling effector 2-oxoglutarate on RNA polymerase binding, open complex formation, and transcript production from promoters of the
hetC
,
nrrA
, and
devB
genes that are activated by NtcA at different stages of heterocyst differentiation. Both RNA polymerase and NtcA could specifically bind to the target DNA in the absence of any effector. 2-Oxoglutarate had a moderate positive effect on NtcA binding, and NtcA had a limited positive effect on RNA polymerase recruitment at the promoters. However, a stringent requirement of both NtcA and 2-oxoglutarate was observed for the detection of open complexes and transcript production at the three investigated promoters. These results support a key role for 2-oxoglutarate in transcription activation in the developing heterocyst.
Purification and Characterization of Active-Site Components of the Putative
p
-Cresol Methylhydroxylase Membrane Complex from
Geobacter metallireducens
Authors: Johannes Jörg , Bluschke Alexander , Jehmlich Nico , von Bergen Martin , Boll Matthias
Published: July 2008

p
-Cresol methylhydroxylases (PCMH) from aerobic and facultatively anaerobic bacteria are soluble, periplasmic flavocytochromes that catalyze the first step in biological
p
-cresol degradation, the hydroxylation of the substrate with water. Recent results suggested that
p
-cresol degradation in the strictly anaerobic
Geobacter metallireducens
involves a tightly membrane-bound PCMH complex. In this work, the soluble components of this complex were purified and characterized. The data obtained suggest a molecular mass of 124 ± 15 kDa and a unique αα′β
2
subunit composition, with α and α′ representing isoforms of the flavin adenine dinucleotide (FAD)-containing subunit and β representing a
c
-type cytochrome. Fluorescence and mass spectrometric analysis suggested that one FAD was covalently linked to Tyr
394
of the α subunit. In contrast, the α′ subunit did not contain any FAD cofactor and is therefore considered to be catalytically inactive. The UV/visible spectrum was typical for a flavocytochrome with two heme
c
cofactors and one FAD cofactor.
p
-Cresol reduced the FAD but only one of the two heme cofactors. PCMH catalyzed both the hydroxylation of
p
-cresol to
p
-hydroxybenzyl alcohol and the subsequent oxidation of the latter to
p
-hydroxybenzaldehyde in the presence of artificial electron acceptors. The very low

K
m

values (1.7 and 2.7 μM, respectively) suggest that the in vivo function of PCMH is to oxidize both
p
-cresol and
p
-hydroxybenzyl alcohol. The latter was a mixed inhibitor of
p
-cresol oxidation, with inhibition constants of a
K
ic
(competitive inhibition) value of 18 ± 9 μM and a
K
iu
(uncompetitive inhibition) value of 235 ± 20 μM. A putative functional model for an unusual PCMH enzyme is presented.
Designation of the Provisional New
Enterococcus
Species CDC PNS-E2 as
Enterococcus sanguinicola
sp. nov., Isolated from Human Blood, and Identification of a Strain Previously Named
Enterococcus
CDC PNS-E1 as
Enterococcus italicus
Fortina, Ricci, Mora, and Manachini 2004
Authors: Carvalho Maria da Glória S. , Steigerwalt Arnold G. , Morey Roger E. , Shewmaker Patricia Lynn , Falsen Enevold , Facklam Richard R. , Teixeira Lucia M.
Published: July 2008

We have previously characterized two new enterococcal species (provisionally designated CDC PNS-E1 and CDC PNS-E2) recovered from clinically significant specimens associated with invasive infections in humans. In the present report we provide additional data and propose formal denominations for isolates of these two species of
Enterococcus
. Results of 16S rRNA gene sequencing, sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of whole-cell protein profiles, and DNA-DNA reassociation experiments indicated that the blood isolate ATCC BAA-780 (SS 1728; CDC PNS-E1) corresponds to
Enterococcus italicus
, whose species epithet was proposed to designate isolates from artisanal Italian cheese. Strain ATCC BAA-781 (CCUG 47861; SS 1729; CDC PNS-E2), a vancomycin-resistant isolate recovered from the blood of a patient in the United States, was found to be highly related at the species level to another blood isolate (SS 1743; CCUG 47884) from Sweden, and for these we propose the designation
Enterococcus sanguinicola
sp. nov.
Lymphoid-Related CD11c+CD8α+Dendritic Cells Are Involved in Enhancing Herpes Simplex Virus Type 1 Latency
Authors: Mott Kevin R. , UnderHill David , Wechsler Steven L. , Ghiasi Homayon
Published: July 2008

The mechanism(s) by which herpes simplex virus type 1 (HSV-1) latency is established in neurons is not known. In this study, we examined the effect of dendritic cells (DCs) on the level of HSV-1 latency in trigeminal ganglia (TGs) of ocularly infected BALB/c and C57BL/6 mice. We found that immunization of wild-type mice with FMS-like tyrosine kinase 3 ligand (Flt3L) DNA, which increases the number of DCs, increased the amount of latency in infected mice. Conversely, depletion of DCs was associated with reduced latency. Latency was also significantly reduced in Flt3L−/−and CD8−/−mice. Interestingly, immunization of Flt3L−/−but not CD8−/−mice with Flt3L DNA increased latency. Transfer experiments using DCs expanded ex vivo with Flt3L or granulocyte-macrophage colony-stimulating factor suggested that increased latency was associated with the presence of lymphoid-related (CD11c+CD8α+) DCs, while reduced latency was associated with myeloid-related (CD11c+CD8α−) DCs. Modulation of DC numbers by Flt3L DNA immunization or depletion did not alter acute virus replication in the eye or TG or eye disease in ocularly infected mice. Our results suggest that CD11c+CD8α+DCs directly or indirectly increase the amount of HSV-1 latency in mouse TGs.
Targeting Tat Inhibitors in the Assembly of Human Immunodeficiency Virus Type 1 Transcription Complexes
Authors: D'Orso Iván , Grunwell Jocelyn R. , Nakamura Robert L. , Das Chandreyee , Frankel Alan D.
Published: July 2008

Human immunodeficiency virus type 1 (HIV-1) transcription is regulated by the viral Tat protein, which relieves a block to elongation by recruiting an elongation factor, P-TEFb, to the viral promoter. Here, we report the discovery of potent Tat inhibitors that utilize a localization signal to target a dominant negative protein to its site of action. Fusing the Tat activation domain to some splicing factors, particularly to the Arg-Ser (RS) domain of U2AF65, creates Tat inhibitors that localize to subnuclear speckles, sites where pre-mRNA processing factors are stored for assembly into transcription complexes. A U2AF65 fusion named T-RS interacts with the nonphosphorylated C-terminal domain of RNA polymerase II (RNAP II) via its RS domain and is loaded into RNAP II holoenzyme complexes. T-RS is recruited efficiently to the HIV-1 promoter in a TAR-independent manner before RNAP II hyperphosphorylation but not to cellular promoters. The “preloading” of T-RS into HIV-1 preinitiation complexes prevents the entry of active Tat molecules, leaving the complexes in an elongation-incompetent state and effectively suppressing HIV-1 replication. The ability to deliver inhibitors to transcription complexes through the use of targeting/localization signals may provide new avenues for designing viral and transcription inhibitors.
Temporal trends in adults’ sports participation patterns in England between 1997 and 2006: the Health Survey for England
Authors: Stamatakis E , Chaudhury M
Published: July 2008

Objective:

To examine temporal trends in participation in sport and exercise activities in England between 1997 and 2006 while taking into account wider societal changes.

Design:

A series of annual cross-sectional surveys.

Setting and participants:

Nationally representative samples of men (n = 27 217) and women (n = 33 721) aged ⩾16 years.

Main outcome measures:

Any (more than once every 4 weeks) and regular (more than once a week) participation in overall sport and exercise and a number of sport and exercise groupings (eg cycling, swimming, gym and fitness club-based activities (G/FC), racquet sports). Time point (1997/98, 2003/04, 2006) was the main dependent variable.

Results:

Age-standardised overall regular participation changed from 40.8% in 1997/98 to 41.2% in 2006 for men (multivariable-adjusted participation OR = 1.11 in 2006, 95% CI 1.03 to 1.19, p<0.001) and from 31.2% to 33.9% for women (1.21, 1.13 to 1.29, p<0.001). Regular G/FC increased from 17.0% to 19.2% for men (1.19, 1.09 to 1.30) and from 15.9% to 18.7% for women (1.23, 1.14 to 1.33) and regular running increased from 2.4% to 4.0% for women only (1.84, 1.56 to 2.18). Overall increases were apparent only in older adults (⩾45 years) (1.25, 1.16 to 1.35, p<0.001). Young men (16–29 years) had reduced ORs for cycling (0.72, 0.58 to 0.88, p = 0.008), dancing (0.60, 0.45 to 0.82, p = 0.001), running (0.78, 0.64 to 0.94, p<0.001) and racquet sports (0.60, 0.42 to 0.86, p = 0.003). In men, increases were pronounced only among men from non-manual social classes, higher income households and white ethnic backgrounds.

Conclusions:

Sports and exercise participation in England has changed between 1997 and 2006 as the result of increases among middle-aged and older adults and decreases among young men. There are no signs that the participation gap between less and more advantaged population groups is narrowing.
The Prediction of Lacustrine Phytoplankton Diversity
Authors: LaZerte Bruce D. , Watson Susan
Published: July 2008

We tested the hypothesis that total phytoplankton biomass can predict phytoplankton community structure independent of its taxonomic composition. From a 2-yr study on Lake Memphremagog, Quebec, which exhibits a marked axial trophic gradient, 133 samples were rarefied to uniform count sizes and a range of diversity numbers, based on proportional biomass, was calculated for each. Biomass is a good predictor of evenness (0.7 < R < 0.9), but not species richness (0.1 < R < 0.3), and this prediction is independent of changes in taxonomic composition. Species richness is more directly related to season and changes in taxonomic composition.Key words: diversity, evenness, species richness, phytoplankton
Discrimination by External Features between Alewife (Alosa pseudoharengus) and Blueback Herring (A. aestivalis)
Authors: MacLellan Patricia , (Buck) Newsome G. E. , Dill Peter A.
Published: July 2008

This study reviews methods formerly recommended for discriminating between the alewife (Alosa pseudoharengus) and blueback herring (A. aestivalis) and suggests an alternate, more efficient, external species-specific character. The method relies on differences in scale imbrication patterns and scale morphology.Key words: alewife, Alosa pseudoharengus; blueback herring, A. aestivalis; morphology, meristics, identification
Empirical Relationships between Bacterial Abundance and Chlorophyll Concentration in Fresh and Marine Waters
Authors: Bird D. F. , Kalff J.
Published: July 2008

A strong, positive empirical relationship was found between bacterial abundance and chlorophyll concentration in fresh and marine waters. Freshwater and marine linear regression equations are statistically indistinguishable. The overall equation is log AODC = 5.867 + 0.776 log chl a, r2 = 0.88, where AODC (acridine orange direct count) is the number of bacteria per millilitre and chl a is micrograms of chlorophyll a per litre. It is apparent that planktonic bacteria and algae are tightly linked in lakes and the sea. The slope of the regression line, however, shows that bacterial numbers do not increase as rapidly as algal biomass with an increase in nutrient concentration. We suggest that this disproportionately smaller increase in bacterial numbers need not signify a smaller role for bacteria in lake metabolism with increasing nutrient availability, if bacterial productivity per unit bacterial biomass increases as total bacterial biomass increases between systems.
Influence of Varying pH and some Inorganic Cations on the Perivitelline Potential of Eggs of Atlantic Salmon (Salmo salar)
Authors: Peterson R. H.
Published: July 2008

A potential difference is maintained between the perivitelline fluid of the Atlantic salmon (Salmo salar) egg and the incubation medium. The magnitude of this potential difference depends on the ionic composition of the incubation medium; it exhibits a maximal negativity in deionized water, then depolarizes, and finally reverses in sign as the ionic content of the incubation medium is raised. The potential difference obeys the Nernst relationship over a limited concentration range of H+, Ca2+, and Mg2+(10−5to 10−3M). The maximal change in potential difference with change in Na+and K+concentrations is less than that predicted by the Nernst equation. The potential difference permits calculation of the degree of concentration of cations in the perivitelline fluid over that of the ambient medium. Depolarizing the perivitelline potential by lowering the ambient pH will result in losses of other cations from the perivitelline fluid.
Differences in Enzyme Frequency and Body Morphology among Three Juvenile Life History Types of Chinook Salmon (Oncorhynchus tshawytscha) in the Nanaimo River, British Columbia
Authors: Carl L. M. , Healey M. C.
Published: July 2008

Chinook salmon (Oncorhynchus tshawytscha), in the Nanaimo River and elsewhere, exhibit three juvenile life history types characterized by different ages at seaward migration. One type migrates to sea immediately after emergence from the spawning gravel and rears in high-salinity estuarine habitats, a second migrates seaward after rearing for about 2 mo in freshwater, and a third type after rearing for a year in freshwater. Nanaimo River chinook were polymorphic at 10 of 31 loci examined electrophoretically. The frequency of allozymes differed significantly among the three life history types at 4 of the 10 loci. A significant deficiency of heterozygotes at the locus for PMI-2 characterized juveniles that reared in estuarine habitats. Fry that died on transfer to salt water in the laboratory had a significant excess of PMI-2 heterozygotes, suggesting that this locus may be associated with salinity adaptation. The three life history types also differed significantly in body morphology. Fish that reared in the estuary had slimmer bodies, smaller heads, and shorter fins than those that reared in the river. Those that spent a year in freshwater had the largest heads, deepest bodies, and longest fins. These observations corroborate the hypothesis that the three life history types represent genetically isolated subpopulations that appear to be physically adapted to their rearing environment. Current plans to increase the numbers of chinook available to commercial and recreational fishermen through artificial propagation of chinook must be made compatible with this degree of genetic variation.
Biochemical Population Genetics of Pacific Halibut (Hippoglossus stenolepis) and Comparison with Atlantic Halibut (H.hippoglossus)
Authors: Grant W. Stewart , Teel David J. , Kobayashi Tokimasa , Schmitt Cyreis
Published: July 2008

The gene products of 35 protein-coding loci were examined for Mendelian variation in three samples of Pacific halibut (Hippoglossus stenolepis) and one sample of Atlantic halibut (H. hippoglossus). Contingency table analyses of allelic frequencies for five polymorphic loci revealed no significant frequency differences between the Bering Sea and the Gulf of Alaska but detected significant Ada-2 frequency differences between these regions and Japan. Average genetic distance between the samples of Pacific halibut was 0.0002 ± 0.0007, and gene diversity analyses showed that 98.7% of the total genetic variation was contained within populations, 0.4% was due to differences between the Bering Sea and the Gulf of Alaska, and 0.9% was due to differences between these regions and Japan. These results are consistent with a larval drift, juvenile migration model of population genetic structure where not all juveniles home to their natal areas. Nei's genetic distance between Pacific and Atlantic halibut was 0.162 ± 0.073, and the molecular clock hypothesis suggests that these species became reproductively isolated from one another in the Pliocene between 1.7 and 4.5 million years ago.
Mortality Rate of Fishes in the Pelagic Ecosystem
Authors: Peterson Ingrid , Wroblewski J. S.
Published: July 2008

A size-dependent equation for mortality rate (M(w)) of fish-sized particles is derived using preexisting theory on the distribution of biomass as a function of size (w) in the pelagic marine ecosystem, assuming that mortality is primarily due to predation. The equation M(w) = ckw−x (where c, k, and x are parameters) yields estimates that are close to observed mortality rates.
Reproductive Capacity of Dragraked and Non-Dragraked Irish Moss (Chondrus crispus Stackhouse) Beds in the Southern Gulf of St. Lawrence
Authors: Chopin T. , Pringle J. D. , Semple R. E.
Published: July 2008

A non-dragraked bed of Chondrus crispus Stackhouse (Rustico) showed a greater year-round carposporangial reproductive capacity than a dragraked bed (Miminegash). The former had a lower frond density but larger fronds which were the major sources of reproduction. Although carposporangial sori had a greater area and were more frequently full in Miminegash, reproductive capacity was higher in Rustico due to higher sorus densities per frond and sample unit. All the studied parameters did not show significant (P = 0.05) differences between the study sites for tetrasporophytes, resulting in similar overall tetrasporangial reproductive capacities. Reproductive capacity peaked in Miminegash prior to the harvesting season. Class 4 and 5 fronds (largest fronds) have the greatest reproductive capacity. To protect this source of spores and thus improve bed reproductive potential, a 1-mo delay in the present season opening date is suggested. The much higher tetrasporophyte reproductive capacity over that of carposporophytes is at least a partial explanation for the greater gametophytic abundance in some populations.
Fatty Acid Composition in Eggs of Atlantic Cod (Gadus morhua)
Authors: Ulvund Kjell Arne , Grahl-Nielsen Otto
Published: July 2008

Fatty acids were determined in single eggs of Atlantic cod (Gadus morhua). The eggs were obtained a few hours after spawning and fertilization from 4-yr-old cod kept in aquaria. By multivariate treatment of the analytical results, the composition of fatty acids was found to vary between eggs within the same spawning batch from the same female. A different variation was found between eggs from the first spawning batch from two different females. The two females had been reared under identical conditions from the egg stage, but were of different sizes at the time of spawning. The fatty acid content in the eggs from the smallest was 4% lower than in the largest. Eggs from the eighteenth spawning batch contained 23% less fatty acids than those from the first batch from the same female. The decrease differed between the acids: the monoenic acids had decreased by 29%, the polyunsaturated acids by 26%, and the saturated acids by 9%.
Assessing the Potential Extent of Damage to Inland Lakes in Eastern Canada due to Acidic Deposition. I. Development and Evaluation of a Simple "Site" Model
Authors: Marmorek David R. , Jones Michael L. , Minns Charles K. , Elder Floyd C.
Published: July 2008

Large scale aquatic effects of acidic deposition have become a prominent environmental issue in North America and Europe. Models are required to assess the potential future impacts of current levels of acidic deposition, and the potential benefits of emission controls. This paper presents a model that uses measurements of current lake chemistry and assumptions about the processes governing acidification, to first estimate original (i.e. preacidification) lake chemistry and then predict the eventual chemistry expected given a specified level of acidic sulphate deposition. The model is deliberately kept simple, so that its input requirements are modest and thus can be met on a regional scale. When applied on a regional scale the model predicts the expected eventual distributions of alkalinity and pH. Application of the model is illustrated for a watershed in north-central Ontario, which includes the area immediately to the south and west of Sudbury. Model-based estimates of current alkalinity are very similar to observed alkalinities. The predicted eventual alkalinity distributions, given current levels of deposition, indicate a trend towards recovery, consistent with other observations in the Sudbury region. A sensitivity analysis of the model indicates that its outputs are highly sensitive to estimates of preacidification lake sulphate levels, and less so to assumptions about the catchment's ability to neutralize incoming acidity. Simple, regional models such as the one presented in this paper should play a more central role than they presently do both in assessment and in the definition of future research and monitoring needs.
Assessing the Potential Extent of Damage to Inland Lakes in Eastern Canada due to Acidic Deposition: II. Application of the Regional Model
Authors: Jones Michael L. , Minns Charles K. , Marmorek David R. , Elder Floyd C.
Published: July 2008

In this, the second of two papers on the development and application of a regional model of surface water acidification, we present the results of initial applications of the model to sensitive regions of eastern Canada. Data used for regional application of the model were obtained from a variety of sources, including acidic sulphate deposition monitoring data and regional lake water chemistry surveys. While these data do not provide a random sample of eastern Canadian lakes, we argue that there are no a priori reasons for expecting highly misleading biases in the data. Results of model applications are presented for observed 1980 sulphate deposition levels and for three alternative emission scenarios. The emission scenarios were simulated using a transfer matrix derived from the AES-LRTAP model. The results suggest that substantial additional damage (declines in surface water alkalinity and pH) is expected in some regions (e.g. northeastern Ontario), even at current deposition levels. The consequences of simple emission reduction strategies differ significantly among regions, suggesting that more complex strategies may be required to produce equitable benefits. To assist interpretation of a complex array of results, we propose an integrated representation of regional impacts that uses quantile-quantile plots of regional distributions of lake chemistry. Finally, we argue that while the results presented are highly uncertain, there are reasons to believe that, if anything, our damage estimates are conservative.
Cascading Effects of Decreased Salinity on the Plankton Chemistry, and Physics of the Great Salt Lake (Utah)
Authors: Wurtsbaugh Wayne A. , Berry Therese Smith
Published: July 2008

Physical, chemical and biological variables were measured in the Great Salt Lake during 1985–87, when salinity in the mixolimnion was near 50 g/L, much lower than the 250 g/L maxima recorded in 1963. Decreased salinity has been accompanied by a change in macrozooplankton from one species (Artemia franciscana), to an assemblage with one rotifer, two copepods, Artemia, and the corixid Trichocorixa verticalis. Predation by the corixid may now limit Artemia to low densities (<100∙m−3). The low biomass of Artemia and other zooplankton has reduced grazing pressure on the algal community so that high chlorophyll levels (5-44 mg∙m−3) and low Secchi depths (0.8–2.7 m) are now present throughout the year. The algae presently reduce soluble reactive phosphorus and inorganic nitrogen in the mixolimnion to below 5 and 50 μg∙L−1, respectively. Shading in the 7-m thick mixolimnion by algae, and by purple-sulfur bacteria in the chemocline, decreases light penetration so that the monimolimnion now maintains a nearly constant temperature (9–11 °C) throughout the year. The data support the hypothesis that the effects of corixid predation have cascaded through the Great Salt Lake, affecting herbivores, nutrients and thermal stratification.
A Fur Seal Population Model Based on Age Structure Data
Authors: Eberhardt L. L.
Published: July 2008

About 16 000 female fur seals from the Pribilof Islands population were aged in pelagic collections from 1958 through 1974. A simple simulation model of the female population was used to vary population parameters until a minimum chi-square value was achieved for the fit of simulated annual age structures to those observed in the pelagic collection. Population trajectories resulting from either a diminishing reproductive rate or diminishing adult female survival rate approximated estimated pup population sizes, which were not used in developing the model, except that a subset of five observations was used to constrain model trajectories to the general neighborhood of the observed pup populations. The main finding of the study was that adult female survival rates varied sharply during the 1964 through 1974 period, after the major period of harvests of female fur seals. Further study of the age structure data may thus be useful in evaluating the poorly understood long-term reduction in abundance of Pribilof fur seals.
Contribution of Rhizosolenia eriensis and Cyclotella spp. to the Deep Chlorophyll Maximum of Sproat Lake, British Columbia, Canada
Authors: Jackson Leland J. , Stockner John G. , Harrison Paul J.
Published: July 2008

Experimental fertilization of Sproat Lake with nitrogen and phosphorus greatly increased the abundance of two centric diatoms: Cyclotella spp. and Rhizosolenia eriensis. A decrease in sinking rates to neutral buoyancy at 17.5–22.5 m, an area of high nutrients and low light, coupled with sedimentation estimates of 106–107 celis∙m−2∙d−1, provide strong evidence that diatoms contribute to the formation of a seasonal deep chlorophyll maximum (DCM). The position of the Sproat Lake DCM, occurring at or just above the 1% light depth, appears to be largely determined by the light regime. R. eriensis bloomed and sank out of the mixed layer early in the spring before lake fertilization began. Immediately after fertilization, concentrations of nitrate and phosphate were elevated for 1 h only in the top 1 m of the water column. Most R. eriensis cells were well below 1 m and benefited little from the nutrient addition because of temporal and spatial separation. Cyclotella spp. occurred in the upper epilimnion and bloomed later in the year and consequently benefited (by large density increases) from fertilization. It is important to consider the temporal and spatial distribution of phytoplankton in determining which species will increase in abundance as a result of areal fertilization.
Effects of Large-Scale Metalimnetic Migration Events on Phosphorus Dynamics In a North-Temperate Reservoir
Authors: James William F. , Kennedy Robert H. , Gaugush Robert F.
Published: July 2008

In Eau Galle Reservoir, Wisconsin, early in the stratified period of 1982, hypolimnetic anoxia developed, soluble reactive phosphorus concentrations increased above the profundal sediment surface, and internal total phosphorus loading was high. Shortly thereafter, the passage of a cold front with high wind power resulted in mixing and a pronounced descent of the metalimnion. During this event, previously anoxic water within the metalimnion and upper hypolimnion became reoxygenated, internal total phosphorus loading declined to a minimum, and a loss of total phosphorus mass occurred from the metalimnion and hypolimnion. Total phosphorus mass in the epilimnion remained constant during this period. A similar pattern occurred during a large, wind-driven migration of the metalimnion in early August. During such events, phosphorus sedimentation rates increased in the hypolimnion, reflecting the loss of total phosphorus mass from the water column. In contrast, other investigations of lakes have reported that phosphorus is entrained into the epilimnion during metalimnetic migrations, rather than lost through sedimentation. Phosphorus sedimentation during large metalimnetic migration events in Eau Galle Reservoir may occur because previously anoxic water containing iron becomes reoxygenated, causing the coprecipitation and sedimentation of oxidized iron and phosphorus.
210Pb/226Ra Determination of Longevity in Redfish
Authors: Campana S. E. , Zwanenburg K. C. T. , Smith J. N.
Published: July 2008

Examination of annular growth rings apparent in charred otolith cross sections is the basis for reports of extreme longevity in the rockfish genus Sebastes, but the interpretation of the annuli has long been disputed. We used a radiochemical assay of the otolith core to confirm our interpretation of annuli in Atlantic redfish, Sebastes mentella, to at least an age of 65 yr. Through measurement of the radioactive disequilibrium between 226Ra and 210Pb, it appears that redfish live to an age of at least 75 yr in the waters off of Nova Scotia.
Intrapopulation Variation in the Breeding of Male Pink Salmon (Oncorhynchus gorbuscha) from a Lake Superior Tributary
Authors: Noltie Douglas B.
Published: July 2008

Studies of breeding pink salmon (Oncorhynchus gorbuscha) from the Carp River, eastern Lake Superior, indicate that males seek fertilizations using two behavioural tactics. In 1985, a large run resulted in high breeding ground densities. During this run, males that resembled females were seen seeking fertilizations by sneaking rather than by competing for proximity to females. Morphological studies in 1985 confirmed the presence of males resembling females, their secondary sexual characters (hump height) being relatively less developed than in typical males. Although in poorer condition, such female-like males were reproductively mature, had returned to spawn at ages typical for this population, and had committed biomass to gonad no differently than had typical males. Furthermore, their spawning performance did not differ from typical males, as assessed both by the amount of gonad they retained unspawned at death and by their spawning ground life expectancies. In contrast, males attempting to sneak fertilizations were not observed during the small 1984 run when densities were low and males were generally in better condition than in 1985. Together, these results indicate that male pink salmon exhibit alternative breeding tactics. However, the demonstration of these tactics appears linked more to proximate factors (density and condition) than to divergent life history strategies as in other salmonid species.
Effects of Aluminum on the Leopard Frog, Rana pipiens: Life Stag Comparisons and Aluminum Uptake
Authors: Freda Joseph , McDonald D. Gordon
Published: July 2008

In this study, we conducted a series of toxicity tests investigating the response of embryos, prestage 25 tadpoles and 3-wk old tadpoles of the leopard frog (Rana pipiens) to a wide range pf pH (4.2–4.8) and Al (0–1000 μg∙:L−1}, and to pH 6.5 with no Al present. In embryos and prestage 25 tadpoles, Al ameliorated the toxic effects of very low pH's (4.2–4.4), while becoming toxic at higher pH's (4.6–4.8). Although both embryos and prestage 25 tadpoles were killed by low pH (pH 4.2–4.4 and 4.2, respectively) and elevated Al ([Formula: see text] and [Formula: see text] Al, respectively), embryos were relatively more sensitive (i.e. higher percent mortality) to low pH, whereas prestage 25 tadpoles were relatively more sensitive to Al Three week old tadpoles did not die at any test pH (without Al) and mortality (>20%) caused by Al occurred at only pH 4.8 and 750–1000 μg∙L−1 Al. The body sodium concentrations of 3-wk old tadpoles that survived high Al exposure were depressed indicating sublethal stress. Whole body Al uptake in 3-wk old tadpoles was also elevated in water containing high concentrations of Al, but it was positively related to water pH and exposure time. This result suggests that body Al content is not an accurate indicator of Al exposure in tadpoles living in acidic, Al contaminated ponds.
Role of Organic Complexation in the Toxicity of Aluminum to Rana pipiens Embryos and Bufo americanus Tadpoles
Authors: Freda Joseph , Cavdek Vandy , McDonald D. Gordon
Published: July 2008

This study investigated the influence of naturally occurring organic compounds on the survival of amphibian embryos and larvae in acidic, aluminum contaminated water. A series of laboratory tests were conducted which measured aluminum toxicity in artificial soft water (ASW) diluted with varying amounts of pond water which contained dissolved organic compounds. At pH 4.5 for tadpoles of Bufo americanus and pH 4.8 for embryos of Rana pipiens, the organic compounds (DOC 5.7 to 16.2 mg∙L−1) complexed the aluminum and thus increased the LC50 for total aluminum by more than two fold. At pH 4.2, 100% ASW and the four dilutions of pond water were toxic to R. pipiens embryos (75–96% mortality), in contrast to higher pH's, aluminum ameliorated acid toxicity which resulted in a 26% reduction in mortality in 100% ASW at 250 mg∙L−1 total aluminum. Although the organic compounds in the pond water also complexed aluminum at pH 4.2, protective levels of labile aluminum [Formula: see text] were still present at 450 μg∙L−1 total aluminum. However, at a given level of labile aluminum in pH 4.2 water, pond water was more toxic to embryos than ASW. At pH 4.2, pond water without added Al was also significantly more toxic to embryos than 100% ASW with 0 μg∙L−1 Al. Toxicity tests using purified humic and fulvic acid sugested that these compounds may be the toxic agents in high dissolved organic carbon (DOC) pond water.
Foraging Movements in Relation to Morphology, Water-Column Use, and Diet for Recently Emerged Brook Trout (Salvelinus fontinalis) in Still-Water Pools
Authors: McLaughlin Robert L. , Grant James W. A. , Kramer Donald L.
Published: July 2008

Recently emerged brook trout (Salvelinus fontinalis) foraging is still-water pools varied considerably in the proportion of time they spent moving, speed while moving, and distance travelled during pursuit of prey. Trout that exhibited a high proportion of time spent moving, fast speeds while moving, and long pursuit distances directed more foraging attempts toward the upper portion of the water column, ate more insect prey and fewer crustaceans, and made more foraging attempts per minute than trout that exhibited a low proportion of time spent moving, slow speeds while moving, and short pursuit distances. The variation in movement was related less strongly to spatial heterogeneity in the locations (pool sizes, water depths) where individuals were observed. It was not significantly related to measures of temporal variation in the environment (date, time-of-day, water temperature), body size and shape, or hunger (the amount of food in the stomach). In these clear, shallow pools, differences in the spatial distribution and behaviour of prey types apparently facilitate divergent foraging behaviour and diet among the trout. Our findings are valuable for understanding the development and maintenance of the individual specializations in water-column use and diet reported previously for several salmonids.
Estimation of Recent Growth of Field-Caught Postlarval American Lobsters,Homarus americanus, from RNA:DNA Ratios
Authors: Juinio Marie Antonette R. , Cobb J. Stanley
Published: July 2008

We developed a growth model for the postlarvae of the American lobster, Homarus americanus, using the relationship of RNA:DNA ratios, temperature, and growth rates during postmolt through early pre-molt of laboratory-reared postlarval lobsters. The model was used to estimate individual growth rates of 385 postlarval lobsters in molt stages C and D0, collected at two sites in Block Island Sound over three years, 1988–90. The mean growth rates of postlarvae collected in June 1989 and 1990 (0.57 ± 0.19 and 0.54 ± 0.18 mg protein∙d−1) were significantly higher than those collected in July (0.39 ± 0.17 and 0.43 ± 0.18 mg protein∙d−1). Changes in sea surface temperatures of zooplankton biomass did not account for the seasonal difference in growth rates, nor was there correlation between the biweekly mean growth rates and postlarval densities. The incidence of poorly nourished postlarval lobsters (individuals with growth rates < 0.22 mg protein∙d−1) was less than 10% of the total samples in each year. We found no evidence that food limitation, resulting in starvation or prolonged duration of the postlarval instar, was a significant factor contributing to the observed interannual variability of postlarval densities.
Transport of Bacillus thuringiensis var. israelensis and Its Effect on Drift and Benthic Densities of Nontarget Macroinvertebrates in the Susquehanna River, Northern Pennsylvania
Authors: Jackson John K. , Sweeney Bernard W. , Bott Thomas L. , Newbold J. Denis , Kaplan Louis A.
Published: July 2008

The microbial pesticide Bacillus thuringiensis var. israelensis (B.t.i.) was applied aerially to suppress larval black fly populations in the Susquehanna River, Pennsylvania. We quantified (1) the passage and retention of B.t.i. spores through a 1.5-km reach and (2) changes in black fly and nontarget macroinvertebrate abundances in the drift and benthos. B.t.i. exposure in the treatment riffle was 1.16 × 105 min-spores/mL or 16 min-mg/L in 1989 and 5.20 × 104 min-spores/mL or 4.4 min-mg/L in 1990. Retention of B.t.i. within the reach was low. While black fly drift from the treatment riffle increased markedly, B.t.i. appeared to have little effect on drift densities of most nontarget macroinvertebrates during the 48-h period following application. Similarly, benthic densities of black flies in the treatment riffle decreased significantly 1 d after the B.t.i. application whereas benthic densities of most nontarget taxa in the treatment riffle and depositional zone appeared unaffected 1, 7, and 28 d following B.t.i. application. Responses potentially related to B.t.i. exposure were observed for the aquatic lepidopteran Petrophila and the chironomid Polypedilum. These results suggest that the application of B.t.i. on the Susquehanna River markedly reduces black fly populations, but does not negatively affect most nontarget macroinvertebrates.
Effects of Dietary Iron Concentrations on the Cytochrome P450 System of Atlantic Salmon (Salmo salar)
Authors: Goksøyr Anders , Bjørnevik Marit , Maage Amund
Published: July 2008

Groups of Atlantic salmon (Salmo salar) parr were fed a basal diet containing 27 mg Fe∙kg feed−1 supplemented with different iron levels (0, 80, and 160 mg∙kg−1, respectively) for 8 wk. After this period, a subgroup of each iron regime was treated intraperitoneally with β-naphthoflavone (BNF), a potent inducer of cytochrome P450 1A1 in fish. Differences between the iron regimes were observed in hepatic iron content, which was higher in the high-iron group, and in P450 1A1 levels and monooxygenase activity, measured as 7-ethoxyresorufin O-deethylase (EROD), which were lower in the high-iron group. Differences were also observed in the induction response of P450 1A1 and EROD to BNF. Levels of a constitutive isozyme denoted P450con, belonging to the P450 3A subfamily, did not respond to the dietary iron in the same manner, demonstrating selective regulatory effects of iron on different P450 isozymes.
Seasonal Effects of Bleached Kraft Mill Effluent on Reproductive Parameters of White Sucker (Catostomus commersoni) Populations of the St. Maurice River, Quebec, Canada
Authors: Gagnon Monique M. , Dodson Julian J. , Hodson Peter V. , Kraak Glen Van Der , Carey John H.
Published: July 2008

Reproductive parameters and accumulation of chlorophenolic compounds by white sucker (Catostomus commersoni) populations exposed to bleached kraft mill effluent (BKME) were studied in the St. Maurice River, Quebec. Compared with unexposed populations from the same waterway, exposed white sucker showed obvious effects of chemical exposure as far as 100 km downstream of the mill, as revealed by a strong induction of ethoxyresorufin O-deethylase (EROD) activity. In males, circulating plasma testosterone levels were the same at all sites, while 11 -ketotestosterone levels were significantly lower at exposed stations. In females, testosterone and 17β-estradiol levels were significantly reduced at the two exposed stations relative to the reference station. Despite different hormone levels during sexual maturation, gonad weight as a proportion of carcass weight was similar at all sites for both sexes during early gonadal development. The relationship between carcass weight and fecundity was more variable at the station immediately downstream of the mill. Biochemical and physiological parameters measured in this study do not allow us to clearly relate perturbations in plasma steroid levels to impaired reproduction as measured by gonad weight and fecundity.
Application of a Generalized Logit Model to Condition Data for Trawl-Caught Pacific Halibut,Hippoglossus stenolepis
Authors: Richards Laura J. , Schnute Jon T. , Fargo Jeff
Published: July 2008

Fisheries data commonly relate a categorical response variable to one or more continuous explanatory variables. We propose a generalized logit model for the analysis of such data. Our model differs from the standard generalized logit model in that transformation parameters for the explanatory variables are estimated simultaneously with other model parameters. We also employ likelihood inference and generic minimization techniques. Our model formulation leads to response surfaces with distinctly different shapes for different levels of the response variable. We illustrate our model with data on the condition of trawl-caught Pacific halibut, Hippoglossus stenolepis, as assessed by observers on commercial trawl vessels. In this data set, the probability of assigning a particular condition level to a fish depends significantly on the time the fish spent on the vessel's deck, fish length, total weight of the catch, tow depth, and tow duration.
Heat and Cold Tolerance of the Fathead Minnow, Pimephales promelas, Exposed to the Synthetic Pyrethroid Cyfluthrin
Authors: Heath Susan , Bennett Wayne A. , Kennedy James , Beitinger Thomas L.
Published: July 2008

Critical thermal maximum (CTMax) and minimum (CTMin) techniques were used to bioassay the effects of sublethal exposures of a synthetic pyrethroid, cyfluthrin, to 240 larval fathead minnows, Pimephales promelas. Fathead minnows were exposed for 24 h to nominal concentrations of cyfluthrin with acetone as a carrier equal to approximately 20 and 70% of the 96-h LC50. Exposure to cyfluthrin caused maximum decreases of 3.3 °C below median heat tolerance of controls (34.4 °C) and a 5.6 °C increase in median cold tolerance above controls (5.9 °C). At the highest concentrations of cyfluthrin tested, the zone of temperature tolerance was reduced by 30%. Concentrations of cyfluthrin that caused these effects were as low as 170 parts per trillion. We believe that this is the first use of CTMin as a bioassay. Although the physical and chemical properties of cyfluthrin may preclude its presence in the environment in large amounts, extremely small concentrations can compromise the ability of fathead minnows to resist extreme temperatures. Cyfluthrin use may have greater adverse effects on nontarget species in northern climates or during colder seasons in southern climates.
Zooplankton Assemblage Responses to Disturbance Gradients
Authors: Stemberger Richard S. , Lazorchak James M.
Published: July 2008

Zooplankton assemblages of 19 New England lakes were evaluated in relation to lake trophic state, riparian land use, fish assemblage features, and physicochemical factors for potential food web indicators of lake ecosystem condition or health. Principal component analysis (PCA) of species abundance data contrasted productive warmwater lakes dominated by rotifers, small cladocerans, and cyclopoid copepods and nauplii with cold-water salmonid systems dominated by calanoid copepods and large cladocerans, and with few rotifers. The use of 12 aggregate zooplankton assemblage variables based on taxonomic group, body size, life-history stage, and feeding guilds improved the amount of the explained cumulative variance (63.2%) over species data (40.3%) in the first two axes of the ordination. In a second PCA the environmental variables were constrained with respect to the zooplankton variables. This analysis identified total phosphorus, chlorophyll a, cold-water fish assemblages, number of introduced fish species, piscivore numbers, and the percentage of disturbed shoreline as dominant gradients. Small-bodied assemblages represented by small cladocerans, rotifers, ostracods, nauplii, and cyclopoid copepodites were associated with the most disturbed systems. The pattern of distribution among large- and small-bodied taxa from the PCA was used to formulate metrics which were then correlated to the gradients.
Role of the Gills and Gill Chloride Cells in Metal Uptake in the Freshwater-Adapted Rainbow Trout,Oncorhynchus mykiss
Authors: Zia S. , McDonald D. G.
Published: July 2008

Fish gills are a primary target of metals from the external environment and serve as a major route for metal uptake. After 12-h exposures to 1 μM109Cd,65Zn, or64Cu in "Ca2+-free" water, gills concentrated metals 3 to 11-fold and contained 38–50% of the total metal burden while sustaining only minor epithelial damage. A twofold increase in chloride cell (CC) surface area had no effect on Cu uptake and actually decreased Zn uptake, confirming that CCs are not primarily involved in the uptake of either metal. In contrast, Cd uptake increased with CC proliferation. Autoradiography revealed a high degree of localization of45Ca in chloride cells confirming their primary role in Ca2+uptake, whereas Cd and Zn were uniformly distributed amongst all gill epithelial cells. Because CCs did not specifically accumulate109Cd, we propose that other effects of softwater acclimation were responsible for the increased uptake of Cd. The only cells in the gills specifically accumulating Cd and Zn were eosinophilic granulocytes localized in the central sinus of gill filaments. Autoradiography of liver and kidney tissue showed uniform distribution of109Cd and65Zn, i.e., there were no cells specifically accumulating metals in these tissues.