bluuebunny/crossref_metadata_2025_split huggingface dataset:
The micro‐distribution of aquatic macroinvertebrates in the Wye river system: the result of abiotic or biotic factors?
Authors: ORMEROD S. J. 
Published: May 2006

SUMMARY. 1. Macroinvertebrates were sampled from three habitats at each of forty‐five sites in the catchment of the Welsh River Wye. Micro‐distribution patterns between three habitat types were assessed for those species which occurred most commonly.2. Of the fifty‐three taxa for which analysis was possible, twenty showed a significant association with habitat type. Eleven occur mostly in margins, eight mostly in riffles, and one in flats (depositing reaches).3. Twenty‐one taxa, including eleven additional to those show significant associations, showed. significant differences between habitats in their relative abundance. Ten were most abundant in margins, eight in riffles and three in flats.4. Factors possibly responsible for these habitat preferences are discussed.
Size‐structure and productivity of the plankton community of an Ethiopian Rift Valley lake
Authors: TAYLOR WILLIAM D. , GEBRE‐MARIAM ZINABU 
Published: May 2006

SUMMARY. 1. We present a broad description of the plankton community of a polymictic freshwater lake in the Ethiopian part of the rift valley of east Africa.2. Despite intermittent stratification, there is little vertical heterogeneity in pico‐, nano‐ or microplankton biomass. Some chemical constituents (O2 NH4, NO3) showed strong vertical differences, as the hypolimnion quickly became anoxic following stratification.3. Phytoplankton biomass and activity is dominated by small Cyanobacteria, although the colonial green alga Botryococcus is also important. Primary productivity probably was limited only by the relationship of light penetration to mixing depth during our experiments, although neither phosphate nor inorganic nitrogen are so abundant that their exhaustion during prolonged stratification is precluded.4. Zooplankton biomass was dominated by small cyclopoid Crustacea, which were mostly absent from surface waters. Cladocera were small and in very low abundance; ciliates and rotifers were more abundant, and probably were the important grazers.5. We speculate that the present plankton community is sustained by strong vertebrate planktivory in the absence of effective piscivores.
Seasonality and spatial variation in abundance, biomass and activity of heterotrophic bacterioplankton in relation to some biotic and abiotic variables in an Ethiopian rift‐valley lake (Awassa)
Authors: GEBRE‐MARIAM ZINABU , TAYLOR WILLIAM D. 
Published: May 2006

SUMMARY. I. Seasonality and spatial variation in abundance, biomass and activity of heterotrophic bacterioplankton was studied in a tropical freshwater lake. Variation in phytoplankton biomass and production, and several other limnological parameters, were also quantified.2. Bacterial number and biomass fluctuated between 3.88–8.33×106 ml−1 and 68–125 mg C m−3, respectively. No spatial variation was observed in these bacterial variables, although other limnological parameters showed vertical variation.3. Seasonal and vertical variation of heterotrophic bacterial activity were estimated from oxygen consumption, 14CO2dark uptake and plate counts of colony forming units. All three methods showed vertical heterogeneity, with higher activity in the hypolimnion during the long stratification period (February May). Oxygen consumption rate and plate counts showed seasonality.4. In spite of the low seasonality of climate in the tropics, several biological, chemical and physical variables were correlated with changes in bacterial variables. Wind and rainfall, and their effects on stratification and mixing, vertical distribution of nutrients and rate of primary production appeared to be the important parameters affecting heterotrophic bacterioplankton.
An evaluation of the metabolism of sestonic and epilithic communities in running waters using an improved chamber technique
Authors: PAUL B. J. , CORNING K. E. , DUTHIE H. C. 
Published: May 2006

SUMMARY. 1. A chamber technique is described which allows the uptake of nutrients in a lotic system to be assessed during a brief experimental period. Sensitive radioisotope techniques were used to determine the metabolism of the planktonic and epilithic communities simultaneously in a pristine boreal forest stream in N.E. Quebec, Canada.2. Abiotic adsorption of bicarbonate, glucose, methylammonium and phosphate was unimportant in the riffle investigated. Among the biological components, the epilithon was responsible for more than 87% of the uptake of bicarbonate, glucose and methylammonium.3. The uptake of orthophosphate was predominantly (80%) by organisms in the overlying water. Phosphorus, the nutrient most limiting the system, may be conserved by the epilithon through internal cycling. Uptake rates are within the range reported for other oligotrophic systems.
Growth responses of planktonic desmid species in a temperature—light gradient
Authors: COESEL PETER F. M. , WARDENAAR KLAASJAN 
Published: May 2006

SUMMARY. 1. Isolates of twelve planktonic desmid species were tested for their growth response in batch culture, using an apparatus that generates crossed gradients of temperature and light intensity.2. Up to 15°C, growth was mainly temperature‐limited. At higher temperatures, there was an increasing effect of light limitation. Optimal growth temperatures were in the range 25–30°C.3. Highest specific growth rates varied from 0.28 to 1.34 day−1. Species with lowest growth rates originated from oligo‐mesotrophic habitats, those with highest growth rates from eutrophic ones.4. Ecophysiological aspects are discussed in some detail, as well as the significance of the experimental data for distributions in the field.
Trace metal chemistry of a Dutch reservoir, the Tjeukemeer
Authors: DE HAAN H. , VOERMAN J. , DE BOER T. , MOED J. R. , SCHROTENBOER J. , HOOGVELD H. L. 
Published: May 2006

SUMMARY.

The concentrations of total and dissolved (<0.2 μm) Fe, Mn, Cu, Co, Zn and Al in the Dutch reservoir, the Tjeukemeer, were recorded fortnightly between 1984 and 1986.
Due to its reservoir function, the Tjeukemeer receives water that is relatively rich in Fe and Mn from its peaty drainage area in winter. In summer, water that is relatively rich in Cu and Zn from lake IJsselmeer, which is flushed by a tributary of the River Rhine, flows into the lake. Therefore trace metal loads, as estimated from annual mean concentrations and hydraulic data, are climate‐dependent.
In wet years, such as 1985, the annual Fe, Mn, Cu and Zn loads may be 3.1,0.2,0.001 and 0.009 gm−2, respectively. In dry years, such as 1984 and 1986, the Fe and Mn loads may be less than one quarter while the Cu and Zn loads may double. Especially in wet years comparable Cu and Zn inputs occur by deposition.
Despite the dependence of trace metal loads on the climate‐dependent water regime. Principal Component Analysis indicated no strong relation between the total Cu, Co, Zn and Al concentrations in lake water and hydrological tracers such as Cl− and UV absorbance. Instead, wind speed appeared to be more strongly connected with the dynamics of these metals. Thus in the shallow Tjeukemeer, internal trace metal loading due to wind‐induced resuspension starts to dominate the contributions of external loads to the total metal concentrations at wind speeds exceeding 3ms−1.
Effects of micrometazoa on the protistan assemblage of a littoral food web
Authors: MCCORMICK PAUL V. , CAIRNS JOHN 
Published: May 2006

SUMMARY.
1. Effects of two size‐classes of micrometazoa (assemblages of rotifers and of rotifers/cladocerans/copepods) on the abundance and composition of a co‐occurring, substrate‐associated protistan assemblage were assessed by selectively transferring these groups from a small pond to laboratory microcosms.2. Addition of micrometazoa to the microcosms resulted in significant changes in the dominance of different protistan groups within 7 days, including a substantial decrease in the abundance of larger omnivorous and bactivorous Protozoa, mostly ciliates, and dominant algal taxa, and an increase in the abundance of heterotrophic microflagellates.3. Mechanisms whereby micrometazoa reduce the abundance of larger heterotrophic protists may include competition for overlapping resources, but probably involves interference and predation as well. Positive effects of Metazoa on the abundance of heterotrophic microflagellates may result from the elimination of ciliates that prey on and compete with smaller Protozoa.4. Interactions indicated in this study may alter both quantitative and qualitative aspects of energy flow and mineral cycling in benthic food‐webs and be part of a larger trophic cascade involving other Metazoa such as fish.
An experimental study on the effects of salamander larvae on isopods in stream pools
Authors: HUANG CHIFU , SIH ANDREW 
Published: May 2006

SUMMARY 1. We used a combination of field surveys and field and laboratory experiments to examine the effects of predatory small‐mouthed salamander larvae, Ambystoma barbouri (Kraus and Petranka), on the density and microhabitat use of benthic isopods, Lirceus fontinalis (Rafinesque).2. A survey of four field stations yielded a significant negative relationship between the densities of salamander larvae and isopods.3. A field experimental manipulation of salamander density confirmed that salamanders reduce isopod density and isopod use of open micro‐habitat. Salamanders did not significantly affect the mean or coefficient of variation in isopod size.4. A laboratory experiment showed that in the absence of refuges for isopods, salamanders were capable of eating large numbers of isopods; small isopods were particularly vulnerable to salamander predation.
Predicting the growth of age‐0 yellow perch populations from measures of whole‐lake productivity
Authors: ABBEY D.H. , MACKAY W.C. 
Published: May 2006

SUMMARY.
1. The relationship was examined between four measures of lake productivity [total phosphorus (TP) and chlorophyll a (Chl a) concentrations, zooplankton density and biomass] and growth in length and weight of age‐0 yellow perch in ten central Alberta lakes.2. In these lakes, average summer TP and Chl a levels were in the range 11–51 and 1.4–19.5 μg1−1, respectively. The interaction of TP and Chl a could explain 61% and 57% of the variance in total length and wet weight, respectively, of age‐0 yellow perch sampled at the end of August.3. The ability to predict first year fish growth from lake productivity is strongest at low levels of productivity (TP<35μgl−1). In the lakes studied, fish community structure is more complex at high levels of productivity (TP>35μg1−1), and more data on complex community level interactions seem necessary to predict fish growth in these systems.
Morphological responses of Daphnia ambigua to different concentrations of a chemical extract from Chaoborus flavicans
Authors: HANAZATO TAKAYUKI , OOI TAKASHI 
Published: May 2006

SUMMARY1. Daphnia ambigua were reared individually with eight different concentrations of a chemical extract from larvae of Chaohorus flavicans, and the frequency of appearance of helmeted individuals and the helmet sizes were determined in the instars 1–6.2. The animals developed most marked helmets in the second instar in response to the extract. The frequency of the helmeted individuals and helmet size in the second instar increased with increasing chemical concentration, although their dose‐response curves differed between them.3. The results may explain the cyclomorphosis of Daphnia, which develop the highest helmets in summer, when the predators are abundant and active, and the concentrations of the predator‐released chemicals would presumably be high.4. The extract became toxic to Daphnia at the highest concentration prepared.
Long‐term patterns of invertebrate stream drift in an Australian temperate stream
Authors: SCHREIBER E.S.G. 
Published: May 2006

SUMMARY1. Invertebrate stream drift was sampled bimonthly in the Acheron River, Victoria, Australia, over a period of 18 months. Replicated hourly samples were collected over a 25‐h period on each sampling date. A total of 194 taxa were identified in the drift. However, total drift density was dominated by few taxa.2. Some evidence was obtained for a seasonal pattern in drift: this was most pronounced in relative abundances of individual taxa and the composition of the drift, rather than in total drift densities. Most of the commonly collected taxa reflected the seasonal pattern of total drift. However, some of the common taxa did not.3. A small number of taxa showed behavioral drift, with a nocturnal increase in drift densities. One species of ‘Baetis’ drifted in high densities over short periods of time around dusk and dawn. It did not drift in higher densities during the night than during the day. The results emphasize the need for drift studies to be more rigorously designed than is typically the case.
Benthic insects in Swedish lake‐outlet streams: patterns in species richness and assemblage structure
Authors: MALMQVIST BJÖRN , ERIKSSON ÅSA 
Published: May 2006

SUMMARY1. We studied how species richness of three hierarchical insect species groups, namely all benthic, lotic and filtering taxa, were related to a number of environmental variables in a data set from fifteen Swedish lake outlets.2. In partial least‐squares analyses, we found that size‐related factors (stream width, discharge) and velocity‐related factors (current velocity, substratum particle size) were positively associated, and productivity‐related factors (chlorophyll a, seston energy, conductivity) negatively associated, with the species richness of the three groups.3. The weak and negative relationship of richness with productivity largely negated theoretical predictions, whereas the species‐environment results corroborated earlier findings from running water systems.4. The most important factors associated with the species composition of the lake outlets studied included pH, lake area, discharge, channel width and detritus.5. Of the filter feeders, most species of blackflies (Diptera: Simuliidae) showed a negative relationship with pH.6. A nested subset analysis demonstrated that species‐poor sites did not have a subset of species found at more species‐rich sites in any of the three hierarchical groups.
Role of PI3‐kinase/Akt signalling pathway in renal function and cell proliferation after renal ischaemia/reperfusion injury in mice
Authors: XIE LIPING , ZHENG XIANGYI , QIN JIE , CHEN ZHAODIAN , JIN YONGFENG , DING WEI 
Published: May 2006

SUMMARY:Background:  PI3K/Akt pathway has been shown to play a critical role in the regulation of mitogenic signalling, apoptosis, cell proliferation and survival in a variety of cells and tissues. The aim of the present study was to investigate the role of PI3K/Akt pathway in the renal ischaemia/reperfusion.Methods:  Four experimental groups, sham‐operative mice, vehicle‐delivered and wortmannin‐treated ischaemic/reperfusion injury mice, wortmannin‐treated normal mice were designed to examined serum blood urea nitrogen level, renal injury, proliferating cell nuclear antigen protein and Akt phosphorylation status at 30 min, 90 min, 24 h, 48 h of reperfusion after ischaemic treatment. Wortmannin or its vehicle was given intraperitoneally at 4 h before surgery. Blood urea nitrogen was measured, and immunohistochemistry and western blotting were used to detect the components of PI3K/Akt pathway in the ischaemic/reperfusion injury kidney.Results:  PI3‐kinase inhibitor wortmannin imposes a deleterious effect on serum blood urea nitrogen level, renal function after renal ischaemia/reperfusion injury in mice. The renal cell proliferation increased after ischaemia/reperfusion injury in mouse, which could be inhibited by wortmannin. Phosphorylation of Akt was increased after ischaemia/reperfusion in the mouse kidney, and reduced by wortmannin administration.Conclusion:  This primary study suggests that PI3‐kinase/Akt signalling pathway play an important role in the regulation of the renal repair after ischaemia/reperfusion injury.
MOLECULAR BASIS FOR THE ROLE OF IRON IN EXPERIMENTAL ALCOHOLIC LIVER INJURY
Authors: Tsukamoto Hidekazu 
Published: May 2006

SummaryThe role of hepatic macrophage‐derived cytokines such as TNFα in the pathogenesis of ALD is plausible. However, the mechanism of TNFα upregulation is not well understood. Our studies to date offer a unique hypothesis that liver injury, induced by ethanol and a high‐fat diet in the intragastric infusion model, primes hepatic macrophages for NF‐κB activation and expression of TNFα, other cytokines, and chemokines, which are under the transcriptional regulation of this factor via enhanced heme turnover and nonheme iron storage by these cells.
Chronic Ethanol Exposure Increases 3H‐GABA Release in Rat Hippocampus by Presynaptic Muscarinic Receptor Modulation
Authors: Hu Ming , Walker Don W. , Vickroy Thomas W. , Peris Joanna 
Published: May 2006

Background: Chronic ethanol treatmcnt (CET) for 28 weeks significantly increases electrically‐stimulated 3H‐GABA release from hippocampal slices. This increase in GABA release may be one of the mechanisms by which CET decreases the magnitude of long‐term potentiation (LTP) in the hippocampus. The present study examined whether CET increases GABA release via an alteration in heterologous presynaptic cholinergic regulation. Methods: Animals were treated with ethanol or sucrose diet for 28 weeks followed by either no withdrawal or a 48‐hr withdrawal period. The electrically‐stimulated 3H‐GABA release from preloaded superfused hippocampal slices of naive and CET rats was measured. Results: Carbachol increased 3H‐GABA release in a concentration‐dependent manner, and atropine modulated 3H‐GABA release in a biphasic concentration‐dependent manner. Atropine (10 μM) significantly blocked the effects of carbachol. Oxotremorine, a selective muscarinic receptor agonist, also incrcased 3H‐GABA release. Mecamylamine, a selective nicotinic antagonist, did not modulate 3H‐GABA releasc and did not block the effects of carbachol. The effects of these agents were also tested in rats 0 or 48 hrs after withdrawal from CET. The biphasic effects of atropine were decreased, whereas the facilitating effects of carbachol were significantly incrcased. There were no changes in the effects of these agents on 3H‐acetylcholine release from hippocampal slices of CET rats compared to sucrose‐treated rats.Conclusion: These results suggest that presynaptic muscarinic receptors facilitate GABA release, whereas nicotinic receptors do not play a significant role in modulating GABA release in hippocampus. CET selectively alters presynaptic muscarinic regulation of GABA release in hippocampus and may help us to further understand the mechanism underlying the disruption of LTP by CET.
Relative Versus Absolute Carbohydrate‐Deficient Transferrin as a Marker of Alcohol Consumption in Patients With Acute Alcoholic Hepatitis
Authors: Halm Ulrich , Tannapfel Andrea , Mössner Joachim , Berr Frieder 
Published: May 2006

Background: Carbohydrate‐deficient transferrin has been described as a sensitive and specific marker for alcohol consumption. This study investigated the usefulness of carbohydrate‐deficient transferrin as a marker of alcohol consumption in acute alcoholic hepatitis. Methods: Absolute concentrations (U/l) and relative values (%) of carbohydrate‐deficient transferrin dctermined in serum with commercial assays, as well as conventional markers for alcohol consumption, were compared with the alcohol consumption (as estimated by a questionaire) in patients with acute alcoholic hepatitis (n= 19), alcoholic liver cirrhosis (n= 37), and nonalcoholic liver diseases (n= 16). Results: The concentration of carbohydrate‐deficient transferrin was increased (p < 0.001) in nonabstaining paticnts (median intake 80 g alcohol/day) with alcoholic liver cirrhosis (45.7 ± 30 U/l), but not in patients with acute alcoholic hepatitis (20.0 ± 7.8 U/l) despite higher alcohol consumption (median 130 gid), nor in abstaincrs with alcoholic livcr cirrhosis (19.4 ± 6.0 U/l) or nonalcoholic liver disease (18.5 ± 6.7 U/l). However, the relative values of carbohydrate‐deficient transferrin were increased both in acute alcoholic hepatitis (7.9 ± 2.1%) and nonabstainers with alcoholic liver cirrhosis (7.4 ± 2.8%), but not in abstaincrs with alcoholic liver cirrhosis (4.6 ± 3.5%) or nonalcoholic liver disease (3.8 ± 0.9%) (p < 0.001). In acute alcoholic hepatitis, the sensitivity and specificity were only 32% and 87% for absolute concentrations, rcspcctively, but 79% and 97% for relative values of carbohydrate‐deficient transferrin. The concentrations of carhohydrate‐deficient and total transferrin in serum were strongly correlated (r= 0.60; p= 0.008). Conclusions: The relative value (% of total), but not the absolute concentration, of carbohydrate‐deficient transferrin in serum is a useful marker of alcohol consumption in acute alcoholic hepatitis.
Ethanol‐Associated Olfactory Stimuli Reinstate Ethanol‐Seeking Behavior After Extinction and Modify Extracellular Dopamine Levels in the Nucleus Accumbens
Authors: Katner Simon N. , Weiss Friedbert 
Published: May 2006

Background: Alcohol craving or automatic behavioral responses provoked by alcohol‐related cues are thought to contribute to relapse risk in abstinent individuals. However, there is to date only limited direct experimental evidence that supports this hypothesis. The present study employed an operant response‐reinstatement model to examine the effects of ethanol‐associated environmental stimuli on alcohol‐seeking behavior and extracellular dopamine (DA) levels in the nucleus accumbens (NAcc).Methods: Male Wistar rats were prepared with intracerebral guide cannulae for microdialysis and trained to operantly self‐administer ethanol in the presence of discrete olfactoIy discriminative stimuli (SΔ's) signaling the availability of ethanol (10% wiv) versus a nonrewarding stimulus (a 50 μM quinine HCl solution). After the discrimination learning phase, responding for ethanol (and quinine) was extinguished by withholding the drinking solutions as well as the corresponding SΔ's. After reaching and maintaining an extinction criterion of ≤ 5 responsesisession, the rats were exposed noncontingently to the ethanol and nonrcward SΔ's but without the availability of ethanol or quinine.Results: The ethanol SΔ's, but not nonreward SΔ's, elicited significant recovery of responding. Exposure to the operant chamber during a 20 min “waiting period” before presentation of the SΔ's was associated with a small but significant increase in dialysate DA levels. Subsequent exposure to the ethanol SΔ and onset of the reinstatement session was accompanied by a small but significant decrease in DA efflux. Exposure to the nonreward SΔ did not alter DA levels.Conclusions: The behavioral data confirm that ethanol‐predictive discriminative stimuli reliably elicit ethanol‐seeking behavior after extinction. The increase in DA efflux during the waiting period confirms earlier findings and suggests that anticipation of access to ethanol activates mesolimbic DA neurons. The decrease in DA efflux after onset of the reinstatement session in animals that were presented with the ethanol SΔ's may reflect neurochemical events associated with the mismatch between the predicted (i.e., ethanol availability) and actual (i.e., absence of ethanol) stimulus events. This possibility is supported by the lack of changes in DA efflux in rats that were presented with the nonreward SΔ's, a test condition that did not involve such a mismatch. Overall, the findings provide further evidence for a role of conditioning processes in the control of alcohol‐seeking behavior and, by extension, support the hypothesis that conditioned responses to drug‐related stimuli may be an important factor in chronic alcohol abuse and relapse.