bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of small scale fluid motion on bacterial growth and respiration
Authors: Bergstedt Maria S. , Hondzo Miki M. , Cotner James B. 
Published: December 2003

Summary1. Laboratory experiments were conducted to investigate the effect of small‐scale turbulent motion on the growth and respiration of bacteria in an oscillating grid apparatus. The experiments were performed under a range of energy dissipation levels similar to those occurring in freshwater systems.2. The results showed that small‐scale turbulent motion does have an effect on bacterial growth and respiration. A higher gradient in the dissolved oxygen time series, higher 5‐day biochemical oxygen demand values, increased bacterial abundance, increased bacterial specific respiration, higher bacterial growth rate and increased nutrient uptake were all observed when the energy dissipation rate in the water column was increased.3. This has implications for traditional laboratory procedures that are used to characterise bacterial metabolic rates under stagnant fluid‐flow conditions, such as biochemical oxygen demand (BOD), which would be influenced by the effects of the small‐scale fluid motion inherent in aquatic environments. According to our results, BOD values in natural systems experiencing fluid motion would be higher than traditional bottle‐derived rates.
Growth‐ and feeding‐related isotopic dilution and enrichment patterns in young‐of‐the‐year yellow perch (Perca flavescens)
Authors: Murchie Karen J. , Power Michael 
Published: December 2003

Summary1. Isotopic signatures (δ15N and δ13C) from young‐of‐the‐year (YOY) yellow perch (Perca flavescens) were collected over the initial 4 month summer growing period from three separate and distinctive sites in northern Alberta, Canada. Data were analysed to test the hypotheses that there are within‐ and among‐population differences in the patterns of isotopic δ15N and δ13C change over the growing season, and that observed isotopic dilution and/or enrichment patterns were influenced by site‐specific physical and chemical factors.2. Increases in δ15N relative to spawned egg masses were observed in immediate posthatch (emergent) YOY and attributed to enrichment associated with the assimilation of yolk during embryonic development.3. Posthatch dilution of YOY δ15N signatures associated with ontogenetic dietary shifts from yolk to exogenous feeding and zooplanktivory to benthivory occurred at all sites and was associated at most sites with a concomitant increase in δ13C.4. The rate and pattern of δ15N dilution and δ13C enrichment observed for the study populations varied between and within sites and depended on maternal trophic status and timing of ontogenetic dietary shifts, as determined by prey availability and site‐specific biogeochemical factors.5. Comparisons of isotopic dilution patterns among species, using results from this study and literature‐derived values, indicated that dilution rates and patterns are species dependent and may vary in relation to key life‐history events.6. Seasonal and spatial isotopic variability among populations and between species complicates field sampling. In particular, the connectivity to site‐specific conditions found here suggests that for locally resident juvenile fishes, spatial, as well as temporal variability must be included in isotopic sampling programmes designed to characterise littoral zone foodweb relationships.
Testing the ecological relevance of Daphnia species designations
Authors: Duffy Meghan A. , Tessier Alan J. , Kosnik Matthew A. 
Published: December 2003

Summary1. Molecular approaches have increasingly revealed hidden genetic structure within ecologically important species, leading to the creation of sibling species whose ecological relevance is often unclear. A prime example is Daphnia galeata mendotae, which was split into D. dentifera and D. mendotae based on differences at two allozyme loci.2. In a set of lake populations in Michigan USA, we test the geographical and temporal consistency of the genetic structure underlying this species split. We also test the morphological relevance of this molecular variation and its ecological significance in lakes. In essence, we ask: does recognition of these new species provide valuable information for plankton ecologists?3. We found that D. dentifera and D. mendotae represent morphologically and ecologically distinct forms that are distributed among lakes in non‐random fashion, which were remarkably stable over 6 years. Key differences between the species concern their body and head shape, vertical habitat use within lakes and distribution among lakes of different size. We hypothesise that these differences represent specialisation to habitats that differ in risk of invertebrate predation.4. Reproductive barriers alone are insufficient to explain the pattern of genetic structure; in some lakes complete introgression is apparent. However, parent species and hybrids exhibit a stable co‐existence in many lakes, which suggests that ecological specialisation reinforces divergence within this taxon.
Saltcedar (Tamarix ramosissima) invasion alters organic matter dynamics in a desert stream
Authors: Kennedy Theodore A. , Hobbie Sarah E. 
Published: December 2003

Summary1. We investigated the impacts of saltcedar invasion on organic matter dynamics in a spring‐fed stream (Jackrabbit Spring) in the Mojave Desert of southern Nevada, U.S.A., by experimentally manipulating saltcedar abundance.2. Saltcedar heavily shaded Jackrabbit Spring and shifted the dominant organic matter inputs from autochthonous production that was available throughout the year to allochthonous saltcedar leaf litter that was strongly pulsed in the autumn. Specifically, reaches dominated by saltcedar had allochthonous litter inputs of 299 g ash free dry mass (AFDM) m−2 year−1, macrophyte production of 15 g AFDM m−2 year−1 and algal production of 400 g AFDM m−2 year−1, while reaches dominated by native riparian vegetation or where saltcedar had been experimentally removed had allochthonous litter inputs of 7–34 g AFDM m−2 year−1, macrophyte production of 118–425 g AFDM m−2 year−1 and algal production of 640–900 g AFDM m−2 year−1.3. A leaf litter breakdown study indicated that saltcedar also altered decomposition in Jackrabbit Spring, mainly through its influence on litter quality rather than by altering the environment for decomposition. Decomposition rates for saltcedar were lower than for ash (Fraxinus velutina), the dominant native allochthonous litter type, but faster than for bulrush (Scirpus americanus), the dominant macrophyte in this system.
Seasonal and inter‐annual scales of variability in phytoplankton assemblages: comparison of phytoplankton dynamics in three peri‐alpine lakes over a period of 28 years
Authors: Anneville O. , Souissi S. , Gammeter S. , Straile D. 
Published: December 2003

Summary1. A method based on hierarchical clustering and Bayesian probabilities is used to identify phytoplankton assemblages and analyse their pattern of occurrence and temporal coherence in three deep, peri‐alpine lakes. The hierarchical properties of the method allowed ranking by order of importance of the effects of changes related to climate and to human activity on the phytoplankton structure.2. The three deep, peri‐alpine lakes (the Lower Zurich, Upper Zurich and Walen lakes) investigated in this study have been monitored since 1972. During that period they have undergone oligotrophication as a result of management programmes and they have been subject to similar meteorological effects that have led to higher water temperatures since 1988.3. The phytoplankton assemblages of the most eutrophic lake (Lower Zurich) differ strongly from those observed in the two meso‐oligotrophic lakes. Local environmental conditions appear to be the main factor responsible for species composition and change in climate characterised by the warmer water temperatures observed since 1988 have had a major impact on the winter composition of the lower basin of Lake Zurich by promoting Planktothrix rubescens.4. Some phytoplankton assemblages are found in all the lakes. Their patterns of occurrence display strong synchrony at the annual and/or inter‐annual scales. However, temporal coherence between the lakes sometimes also involves different assemblages.5. The reduction in phosphorus had a great influence on long‐term changes in composition. In all three lakes, decreases in phosphorus are associated with a community characterised by some mixotrophic species or species adapted to low nutrient concentrations or sensitive to transparency. In the Lower Lake Zurich the decrease in phosphorus has also led to the development of species adapted to low light intensities.6. Seasonal meteorological forcing has also induced synchronous changes, but the same assemblages are not necessarily involved, because the pool of the well‐placed candidate taxa that may develop is determined by the local environmental conditions, and mainly by phosphorus concentrations. In the most eutrophic lake, the seasonal pattern is characterised by a succession of more stages. However, the seasonal assembly dynamics involve the succession of species sharing common selective advantages that make them relatively stronger under these nutrient and light conditions.
Larval fish‐induced phenotypic plasticity of coexistingDaphnia: an enclosure experiment
Authors: Bernot Randall J. , Dodds Walter K. , Quist Michael C. , Guy Christopher S. 
Published: December 2003

Summary1. The indirect effects of predators on lower trophic levels have been studied without much attention to phenotypically plastic traits of key food web components. Phenotypic plasticity among species creates phenotypic diversity over a changing environmental landscape.2. We measured the indirect effects of planktivorous larval walleye (Stizostedion vitreum) on phytoplankton biomass through their effects on the dominant herbivore species,Daphnia pulicariaandD. mendotae.3. Fish had no effect on phytoplankton biomass or overallDaphniadensity. We observed a compensatory response to predation by functionally comparable species within a trophic level in the form of shifting dominance and coexistence ofDaphniaspecies. We hypothesized that this phenotypically plastic response to predation decoupled a potential trophic cascade in this freshwater pelagic system.Daphnia pulicariadensity decreased over time with fish predation, butD. mendotaedensity increased over time with fish predation.4. Phenotypically plastic life history trait shifts and reproductive rates differed between species in fishless and fish enclosures, accounting for population trends.Daphnia pulicariawere also proportionally higher in walleye larvae stomachs than in the enclosures, indicating that walleye preferred to feed onD. pulcariaoverD. mendotae. The resultant shift in dominance may partially explain the overall benign effect of fish on grazers and supports the hypothesis that trophic level diversity can decouple a trophic cascade.
Selective grazing by adults and larvae of the zebra mussel (Dreissena polymorpha): application of flow cytometry to natural seston
Authors: Dionisio Pires L. M. , Jonker R. R. , Van Donk E. , Laanbroek H. J. 
Published: December 2003

Summary1. Selective grazing of adults and larvae of the zebra mussel (Dreissena polymorpha) on phytoplankton and detritus from both laboratory cultures and natural seston was quantified using flow cytometry.2. Mean clearance rate of adult zebra mussels was higher on a mixture of the green alga Scenedesmus and the cyanobacterium Microcystis than when Scenedesmus was offered as single food, suggesting selective feeding by the mussels.3. Feeding on lake seston both adults and larvae showed a higher clearance rate on phytoplankton than on detritus particles, suggesting that zebra mussels select for phytoplankton. Furthermore, it was noted that adults preferred seston particles in the 0–1 and 30–100 μm size ranges.4. In our study, zebra mussels did not discriminate against cyanobacteria, and our results indicate that they may even ingest them preferentially.
Neuropeptide‐Y Y5 Receptors Modulate the Onset and Maintenance of Operant Ethanol Self‐Administration
Authors: Schroeder Jason P. , Iller Kimberly A. , Hodge Clyde W. 
Published: December 2003

Background: Neuropeptide Y (NPY) is the most abundant and widely distributed peptide in the mammalian central nervous system and increases feeding behavior at NPY Y1 or Y5 receptor subtypes. Recent pharmacological and mutant mouse data indicate that NPY activity at its receptors can influence ethanol self‐administration, although the direction and strength of this influence are not clear.Methods: Effects of the novel NPY Y5 receptor antagonist L‐152,804 on the onset and maintenance of operant self‐administration were examined in male C57BL/6J mice, which were trained to self‐administer ethanol (10% v/v) versus water via the sucrose substitution method during 16 hr overnight sessions. After 4 months of baseline responding, mice were injected with L‐152,804 (0, 10, 30, or 60 mg/kg, intraperitoneally) before operant sessions. Potential locomotor effects of L‐152,804 and possible interaction with the sedative properties of ethanol also were examined.Results: All three doses of L‐152,804 significantly delayed the onset of ethanol‐reinforced responding relative to vehicle injection. L‐152,804 produced no effect on the total number of ethanol‐ or water‐reinforced responses per 16 hr session. However, L‐152,804 selectively modulated the temporal distribution of ethanol‐reinforced responding depending on the dose (10 and 60 mg/kg) and time point measured in a manner consistent with blockade of ethanol reinforcement. Additional experiments determined that L‐152,804 (10 or 60 mg/kg) did not alter spontaneous locomotor activity or influence the sedative effects of ethanol (4 g/kg).Conclusions: These results indicate that blockade NPY Y5 receptor activity modulates the onset and maintenance of ethanol self‐administration. For this reason, NPY‐Y5 receptor antagonists may be useful in medical management of alcohol abuse and alcoholism.
Ethanol Sensitivity of Recombinant Homomeric and Heteromeric AMPA Receptor Subunits Expressed in Xenopus Oocytes
Authors: Akinshola B. Emmanuel , Yasuda Robert P. , Peoples Robert W. , Taylor Robert E. 
Published: December 2003

Background: Ethanol is known to acutely inhibit AMPA receptor function, and sensitivity of AMPA receptors to ethanol is dependent on subunit composition in vivo and in vitro. A commonly used in vitro expression system for studying recombinant receptor subunits is the Xenopus laevis oocyte and two‐electrode voltage‐clamp electrophysiological recording. To date, ethanol sensitivity of injected receptor subunit complementary RNA (cRNA) has not been shown to be correlated with the actual expression of receptor subunits in oocytes. In this study, we compared ethanol sensitivity of homomeric and heteromeric AMPA receptor subunits microinjected into Xenopus oocytes and confirmed subunit expression in oocytes by immunoblot.Methods: cRNAs coding for the “flop” type AMPA GluR1 or GluR3 (homomeric), GluR2/GluR3 (heteromeric combination), and GluR1/2/3 (heteromeric combination) were microinjected in equimolar amounts of 16 to 20 ng into oocytes, which were studied for their sensitivity to ethanol. Oocytes injected with cRNA for homomeric or heteromeric subunit combinations were homogenized and the expressed subunits quantified with anti‐GluR1, anti‐GluR2, and anti‐GluR2/3 antibodies.Results: Ethanol concentrations of 10 to 500 mM consistently inhibited currents activated in oocytes by 200 μM kainic acid. The expressed homomeric GluR1 receptor and heteromeric GluR1/2/3 receptor combination currents showed similar sensitivity to ethanol inhibition with half‐maximal inhibition values of 170 ± 12 mM and 176 ± 8 mM, respectively. The expressed homomeric GluR3 receptor and heteromeric GluR2/3 receptor combination currents were differentially sensitive to ethanol inhibition with respective IC50 values of 238 ± 9 mM and 338 ± 16 mM.Conclusion: The expressed homomeric and heteromeric “flop” type AMPA receptors were differentially sensitive to ethanol, which may in part explain differential ethanol sensitivity in native neurons.
Intra‐Amygdala Infusion of the NPY Y1 Receptor Antagonist BIBP 3226 Attenuates Operant Ethanol Self‐Administration
Authors: Schroeder Jason P. , Olive Foster , Koenig Heather , Hodge Clyde W. 
Published: December 2003

Background: Neuropeptide Y (NPY) is the most abundant and widely distributed peptide in the mammalian central nervous system. Evidence suggests that NPY transmission at Y1 receptors may regulate alcohol self‐administration in rodent models. The purpose of the present study was to test the involvement of NPY Y1 receptors in the amygdala in the reinforcing effects of alcohol.Methods: Long‐Evans rats were trained to self‐administer ethanol (10% v/v) vs. water on a concurrent FR‐1 schedule of reinforcement using a sucrose fading procedure. After a 1 month baseline period, bilateral injector cannulae were surgically implanted to terminate 1 mm dorsal to the central nucleus of the amygdala. Daily (Monday through Friday) operant self‐administration sessions were conducted for 6 months after surgery. Then, the effects of intra‐amygdala infusion of the high‐affinity nonpeptide NPY Y1 receptor antagonist BIBP 3226 (1, 10, or 20 μMg) were determined on parameters of operant alcohol self‐administration.Results: Intra‐amygdala administration of 10 μM or 20 μM BIBP 3226 decreased total alcohol‐reinforced responding and dose of self‐administered ethanol (g/kg) without significantly altering total water responses or intake compared with vehicle control. Response onset was unaffected. Analysis of the temporal pattern of ethanol‐ and water‐reinforced responding showed that BIBP 3226 decreased cumulative ethanol‐reinforced responding during the 30 to 60 min period of the sessions. Water‐reinforced responses were increased by the low dose of BIBP 3226 (1 μM) during the 50 to 60 min period.Conclusions: Results from this study indicate that alcohol‐reinforced responding is reduced by acute blockade of NPY Y1 receptors in the amygdala of rats with a long‐term history of alcohol self‐administration. These data are consistent with the hypothesis that alcohol self‐administration is maintained by NPY neurotransmission at Y1 receptors in the central nucleus of the amygdala.
Serotonergic Agents and Alcoholism Treatment: A Simulation
Authors: Stoltenberg Scott F. 
Published: December 2003

Background: Those with early‐onset alcoholism may better respond to ondansetron (a 5‐HT3 receptor antagonist) than to selective serotonin reuptake inhibitor (SSRI) treatment, whereas those with late‐onset alcoholism may present the reverse response pattern. Johnson and colleagues proposed a model that attempts to explain the observed treatment response patterns of those with early and late alcoholism onset by focusing on the influence of a common genetic variant in the serotonin transporter regulatory region (5‐HTTLPR) on serotonin (5‐HT) and dopamine (DA) system function.Methods: The present study formalizes and extends Johnson's descriptive model into a computer simulation consisting of differential equations. For each of 16 conditions defined by genotype, drinking status, diagnostic status, and drug treatment, data were generated by 100 simulation runs.Results: In every condition, the S/_ genotype (S/S and S/L) had higher extracellular 5‐HT levels than did the L/L genotype. The S/_ genotype also had higher rates of postsynaptic DA firing than did the L/L genotype with the exception of the SSRI treatment condition, where the firing rates were similar. Drinking generally increased levels of extracellular 5‐HT, reduced rates of presynaptic 5‐HT firing, and increased rates of postsynaptic DA firing. Drinking produced increases in DA activation that were greater for the L/L genotype in the SSRI treatment condition and for the S/_ genotype in the ondansetron treatment condition.Conclusions: Genotype at 5‐HTTLPR may influence relative reward of drinking alcohol while a person is under pharmacological treatment for alcoholism. Alternatively, 5‐HTTLPR genotype may influence pathways of alcohol craving. Clinical studies should examine these hypotheses.
Prenatal Ethanol Exposure Modifies [3H]MK‐801 Binding to NMDA Receptors: Spermidine and Ifenprodil
Authors: Honse Yumiko , Randall Patrick K. , Leslie Steven W. 
Published: December 2003

Background: It has been suggested that abnormalities seen in fetal alcohol syndrome are linked with NMDA receptor malfunction. Our laboratory has previously shown that prenatal ethanol treatment decreases [3H]MK‐801 binding density at postnatal day 21, when NMDA receptor subunit protein levels were unaltered. Thus, the focus of the present study was to examine whether prenatal ethanol modifies native NMDA receptor levels.Methods: Cerebral cortices were taken from offspring born to three treatment groups of pregnant Sprague Dawley® rats: an ethanol group given an ethanol liquid diet during the gestational period, a pair‐fed control group that received a liquid diet without ethanol, and an ad libitum group fed rat chow and tap water. Western blot studies were carried out at postnatal days 1, 7, 14, and 21 to examine total protein expression of NR1 and NR1b splice variants. NR2 subunit levels were examined by [3H]MK‐801 binding studies using spermidine, an endogenous polyamine, and ifenprodil, a selective NR2B antagonist.Results: [3H]MK‐801 binding density was significantly reduced in prenatal ethanol‐treated groups compared with ad libitum and pair‐fed control groups. Spermidine increased [3H]MK‐801 binding, although potentiation by spermidine was not significantly different among all three experimental groups. Furthermore, no significant differences in total protein expression of NR1 or NR1b splice variants were observed in cortical membrane homogenates at postnatal days 1 through 21. [3H]MK‐801 binding in the presence of ifenprodil showed that prenatal ethanol treatment significantly decreased low‐affinity ifenprodil binding. High‐affinity ifenprodil binding was reduced in both pair‐fed and ethanol‐treated groups.Conclusions: These results suggest that prenatal ethanol treatment reduces [3H]MK‐801 binding and that this reduction may be due to a decrease in NR2A subunits.
Generation of Aldehyde‐Derived Protein Modifications in Ethanol‐Exposed Heart
Authors: Niemelä Onni , Parkkila Seppo , Worrall Simon , Emery Peter W. , Preedy Victor R. 
Published: December 2003

Background: Although excessive ethanol consumption is known to lead to a variety of adverse effects in the heart, the molecular mechanisms of such effects have remained poorly defined. We hypothesized that posttranslational covalent binding of reactive molecular species to proteins occurs in the heart in response to acute ethanol exposure.Methods: The generation of protein adducts with several aldehydic species was examined by using monospecific antibodies against adducts with malondialdehyde (MDA), acetaldehyde (AA), MDA‐AA hybrids, and hydroxyethyl radicals. Specimens of heart tissue were obtained from rats after intraperitoneal injections with alcohol (75 mmol/kg body weight) with or without pretreatment with cyanamide (0.05 mmol/kg body weight), an aldehyde dehydrogenase inhibitor.Results: The amounts of MDA and unreduced AA adducts were found to be significantly increased in the heart of the rats treated with ethanol, cyanamide, or both, whereas no other adducts were detected in statistically significant quantities. Immunohistochemical studies for characterization of adduct distribution revealed sarcolemmal adducts of both MDA and AA in the rats treated with ethanol and cyanamide in addition to intracellular adducts, which were also present in the group treated with ethanol alone.Conclusions: These findings support the role of enhanced lipid peroxidation and the generation of protein‐aldehyde condensates in vivo as a result of excessive ethanol intake. These findings may have implications in the molecular mechanisms of cardiac dysfunction in alcoholics.