bluuebunny/crossref_metadata_2025_split huggingface dataset:
A model approach to planktonic stoichiometry and consumer‐resource stability
Authors: HESSEN DAG , BJERKENG BIRGER 
Published: November 2003

1. The model explores stoichiometric feedback effects between an alga and a grazer (Daphnia) in a simplified chemostat‐type system in stagnant conditions or with fixed dilution rate.2. When running the model with fixed stoichiometry and P‐sufficient food, the grazer with highest requirements for phosphorus (P) will exert the most efficient control of algal biomass owing to more P being allocated to zooplankton biomass and less P recycled.3. When including potential P‐limitation of the grazer, the grazer with high P requirements (high P : C ratio) will be the least efficient grazer in a system with fluctuating and temporarily low P : C ratio in algae (Qa).4. Qualitatively deficient food will yield decreased growth efficiency in zooplankton. As Qa decreases, the grazer isocline for zero net growth is shifted upwards, and the required algal biomass for positive growth increases. There may then be a critical level of Qa below which the grazer with high P : C suffers negative population growth regardless of algal biomass. In cases with low minimum Qa and a P‐demanding grazer, this may cause the system to enter an irreversible stage with high biomass of P‐deficient phytoplankton which do not support zooplankton growth.5. Cumulative primary production for scenarios with continuous P input is, in general, higher the more Qa is allowed to drop below saturation values, and highest when this is combined with a grazer with a high P : C ratio. The lower growth rate of P‐deficient phytoplankton was compensated for by reduced success of the P‐limited grazer, yielding low grazing pressure and resulting in larger phytoplankton biomass.
Effects of enhanced ultraviolet‐B radiation on the production of lipid, polysaccharide and protein in three freshwater algal species
Authors: ARTS MICHAEL , RAI HAKUMAT 
Published: November 2003

1. The effects of ultraviolet‐B (UVB‐enhanced) radiation on the production of photosynthates (lipid, protein, polysaccharide and low molecular weight compounds) was examined for three species of algae. Cryptomonas sp., Nitzschia palea and Synechococcus elongatus were selected as representatives of the Cryptophyceae, Bacilliarophyceae and Cyanobacteria, respectively.2. Laboratory experiments were performed at several UVBweighted dose rates ranging from 0.018 to 0.391 mW cm–2. These dose rates span the range of dose rates used in other studies.3. Effects on the overall photosynthetic rate were observed, even at relatively low UVBweighted dose rates (0.047 mW cm–2).4. The effect of UVB radiation on the fixation of carbon into the main macromolecular pools differed, depending not only on the dosage but on the species examined. However, the observed inhibitory effects were generally non‐stochastic. In addition, within each species there were differences in the apparent sensitivity of the various fractions to inhibition by UVB radiation.5. These results suggest that exposure to UVB radiation has the potential to alter the relative allocation of recently fixed carbon to lipid, protein, polysaccharide and low molecular weight compounds in algae in a species‐specific manner.
Can physicochemical factors predict lipid content in phytoplankton?
Authors: WAINMAN B.C. , SMITH R.E.H. 
Published: November 2003

1. We hypothesized that a large collection of reasonably standardized data for natural algal assemblages would reveal the influence of environmental factors on the fraction of recently produced photosynthate allocated to lipid.2. Our analysis of photosynthate allocation in fresh‐ and saltwater systems showed that allocation of carbon to lipid was not well correlated with any one environmental factor.3. Allocation to lipid increases with temperature up to 12 °C (lipid allocation = 11.7 + 1.70*temperature (°C), n = 48, r2 = 0.50, P < 0.001) but not above.4. The relationship between temperature and lipid allocation appears to be caused by a unique convergence of nutrient limitation (nitrate or silicate) in the presence of facultative lipid‐producing algae (diatoms or other chrysophytes) which occurs at or below 12 °C during stratification of the water column.
Effects of fatty acid and phosphorus content of food on the growth, survival and reproduction ofDaphnia
Authors: SUNDBOM MARCUS , VREDE TOBIAS 
Published: November 2003

1. Mixtures of microencapsulated lipids and Scenedesmus quadricauda grown at different degrees of P limitation were used as food for Daphnia galeata in two growth experiments. Thereby, food quality in terms of ω3‐fatty acid (ω3‐FA) or phosphorus (P) content could be assessed without interference from other factors.2. ω3‐highly unsaturated fatty acids (ω3‐HUFA), given to Daphnia as fish oil or eicosapentaenoic acid (EPA) together with non P‐limited algae, decreased the time to first reproduction. When fed fish oil, somatic growth and survival were also enhanced. Linolenic acid also decreased the time to first reproduction but to a lesser extent than EPA.3. Food quality depended to a large extent on the degree of P limitation of Scenedesmus, which is consistent with P limitation of Daphnia. The overall impact of P was always larger than the effect of ω3‐FA. Growth, survival and reproduction were elevated when Daphnia were fed non P‐limited Scenedesmus compared to treatments with P‐limited algae.4. The relative importance of ω3‐HUFA and P content in the food changed over a C : P gradient, with stronger effects of ω3‐HUFA at low C : P ratios.
Effect of the addition of polyunsaturated fatty acids to the diet on the growth and fecundity ofDaphnia galeata
Authors: WEERS PAUL , GULATI RAMESH 
Published: November 2003

1. The importance of long‐chain polyunsaturated fatty acids (PUFAs), in particular eicosapentaenoic acid (EPA), for the growth and development of Daphnia galeata (Sars) was tested using food types differing in PUFA and EPA contents.2. Life history experiments of D. galeata fed with the cryptophyceans Rhodomonas lacustris (Pascher & Ruttner) and Cryptomonas pyrenoidifera (Gentler), and the green alga Scenedesmus acutus (Meyen), showed that both cryptophycean species were higher in quality than S. acutus.3. Since the cryptomonads contained significant amounts of EPA while no EPA could be detected in Scenedesmus, tests were performed to ascertain whether EPA was responsible for the differences in food quality. Feeding daphnids a mixed diet of Scenedesmus and emulsion particles that were rich in EPA and DHA, resulted in a significant improvement in the intrinsic population growth rate. The initial difference in food quality between Scenedesmus and the cryptomonads was completely compensated for by addition of emulsion to the Scenedesmus food.4. From the observed stimulatory effect of the addition PUFA to the daphnid diet, this study concludes that the presence of such long‐chain PUFA improves food quality for daphnids.
Use of fatty acids for the assessment of zooplankton grazing on bacteria, protozoans and microalgae
Authors: DESVILETTES CH. , BOURDIER G. , AMBLARD CH. , BARTH B. 
Published: November 2003

1. The distribution of fatty acids in different groups of bacteria, ciliated protozoans and microalgae is reviewed emphasizing specific fatty acids like odd‐branched fatty acids and (n‐3) polyunsaturated fatty acids.2. Odd‐branched fatty acids and (n‐6) fatty acids appear to be good indicators of zooplankton grazing on bacteria and ciliates when they are detected in microcrustacean triacylglycerols. We give several examples where these fatty acids may be used as markers. The value of (n‐3) fatty acids in describing zooplankton grazing on phytoplankton seems to be low.
Effects of food type on the life history of Daphnia clones from lakes differing in trophic state. II. Daphnia cucullata feeding on mixed diets*
Authors: REPKA SARI 
Published: November 2003

1. The effects of feeding on suboptimal foods were investigated in Daphnia cucullata a zooplankton common in many types of lakes. Eleven clones of D. cucullata were collected from four lakes of varying trophic levels and fed a high (1 mg C l–1) concentration of one of two diets: (i) a 1 : 9 mixture of the cryptophyte Cryptomonas pyrenoidifera with the green alga Scenedesmus obliquus; and (ii) a 1 : 9 mixture of the cryptophyte C. pyrenoidifera with the filamentous cyanobacterium Oscillatoria limnetica.2. As expected, the diet dominated by Oscillatoria was found to be significantly poorer compared with the diet dominated by Scenedesmus. All D. cucullata clones were, however, able to achieve positive population growth rates on both diets, supporting the view that daphnids can grow and reproduce on a diet dominated by filamentous cyanobacteria.3. Clones originating from different types of lakes differed in their responses to the two diets. On the Scenedesmus‐dominated diet, clones originating from moderately eutrophic lakes had lower population growth rates than clones from hypertrophic lakes. In contrast, on the Oscillatoria‐dominated diet, the clones from moderately eutrophic lakes had higher population growth rates than clones from hypertrophic lakes. Contrary to expectation, clones originating from lakes dominated by filamentous cyanobacteria had more difficulty utilizing filamentous cyanobacteria as food than clones from less eutrophic lakes which contain less filamentous cyanobacteria.4. As the reactions of clones originating from same type of lake resembled each other, it is hypothesized that the life histories of D. cucullata populations are locally adapted to environmental factors other than abundance of filamentous cyanobacteria, which are correlated with trophic levels.
Temperature effect on inclusion body formation and stress response in the periplasm of Escherichia coli
Authors: Hunke Sabine , Betton Jean‐Michel 
Published: November 2003

SummaryWe previously characterized a defective‐folding mutant of maltose‐binding protein of Escherichia coli, MalE31, which formed periplasmic inclusion bodies. Here, we show that MalE31 aggregation does not affect bacterial growth at 30°C but is lethal at 37°C. Surprisingly, under mild heat shock conditions at 42°C, inclusion bodies are degraded and bacterial growth is restored. One physiological consequence for the cells overproducing MalE31 was to induce an extracytoplasmic stress response by increasing the expression of the heat shock protease DegP via the CpxA/CpxR two‐component signalling pathway. Furthermore, we show that the Cpx response is required to rescue the cells from the toxicity mediated by MalE31. Finally, expression of highly destabilized MalE variants that do not aggregate in the periplasm also induces the Cpx pathway, indicating that inclusion body formation is not necessary to activate this specific extracytoplasmic stress regulatory system.
Cell wall stress responses in Bacillus subtilis: the regulatory network of the bacitracin stimulon
Authors: Mascher Thorsten , Margulis Neil G , Wang Tao , Ye Rick W. , Helmann John D. 
Published: November 2003

SummaryIn response to sublethal concentrations of antibiotics, bacteria often induce an adaptive response that can contribute to antibiotic resistance. We report the response of Bacillus subtilis to bacitracin, an inhibitor of cell wall biosynthesis found in its natural environment. Analysis of the global transcriptional profile of bacitracin‐treated cells reveals a response orchestrated by two alternative σ factors (σB and σM) and three two‐component systems (YvqEC, YvcPQ and BceRS). All three two‐component systems are located next to target genes that are strongly induced by bacitracin, and the corresponding histidine kinases share an unusual topology: they lack about 100 amino acids in their extracellular sensing domain, which is almost entirely buried in the cytoplasmic membrane. Sequence analysis indicates that this novel N‐terminal sensing domain is a characteristic feature of a subfamily of histidine kinases, found almost entirely in Gram‐positive bacteria and frequently linked to ABC transporters. A systematic mutational analysis of bacitracin‐induced genes led to the identification of a new bacitracin‐resistance determinant, bceAB, encoding a putative ABC transporter. The bcrC bacitracin resistance gene, which is under the dual control of σX and σM, was also induced by bacitracin. By comparing the bacitracin and the vancomycin stimulons, we can differentiate between loci induced specifically by bacitracin and those that are induced by multiple cell wall‐active antibiotics.
Cyclophilin A and calcineurin functions investigated by gene inactivation, cyclosporin A inhibition and cDNA arrays approaches in the phytopathogenic fungusBotrytis cinerea
Authors: Viaud Muriel , Brunet‐Simon Adeline , Brygoo Yves , Pradier Jean‐Marc , Levis Caroline 
Published: November 2003

SummaryCalcineurin phosphatase and cyclophilin A are cellular components involved in fungal morphogenesis and virulence. Their roles were investigated in the phytopathogenic fungusBotrytis cinereausing gene inactivation, drug inhibition and cDNA macroarrays approaches. First, theBCP1gene coding for cyclophilin A was identified and inactivated by homologous recombination. Thebcp1Δnull mutant obtained was still able to develop infection structures but was altered in symptom development on bean and tomato leaves. Opposite to this, calcineurin inhibition using cyclosporin A (CsA) modified hyphal morphology and prevented infection structure formation. CsA drug pattern signature on macroarrays allowed the identification of 18calcineurin‐dependent (CND) genes among 2839B. cinereagenes. Among the co‐regulatedCNDgenes, three were shown to be organized as a physical cluster that could be involved in secondary metabolism. The signature ofBCP1inactivation on macroarrays allowed the identification of only three BCP1cyclophilin‐dependent (CPD) genes that were different fromCNDgenes. Finally, no CsA drug pattern signature was observed in thebcp1Δnull mutant which provided a molecular target validation of the drug.
Evidence for the importance of genetic structuring to the structural and functional specialization of the Plasmodium falciparum var gene family
Authors: Kraemer Susan M. , Smith Joseph D. 
Published: November 2003

SummaryThe var gene family encodes Plasmodium falciparum erythrocyte membrane 1 (PfEMP1) proteins that act as virulence factors responsible for both antigenic variation and cytoadherence of infected erythrocytes. These proteins orchestrate infected erythrocyte sequestration from blood circulation and contribute to adhesion‐based complications of P. falciparum malaria infections. For this study, we analysed the genetic organization and strain structure of var genes and present evidence for three separately evolving groups that have, in part, functionally diverged and differ between subtelomeric and central chromosomal locations. Our analyses suggest that a recombination hierarchy limits reassortment between groups and may explain why some var genes are unusually conserved between parasite strains. This recombination hierarchy, coupled with binding and immune selection, shapes the variant antigen repertoire and has structural, functional and evolutionary consequences for the PfEMP1 protein family that are directly relevant to malaria pathogenesis.
The RcsC sensor kinase is required for normal biofilm formation in Escherichia coli K‐12 and controls the expression of a regulon in response to growth on a solid surface
Authors: Ferrières Lionel , Clarke David J. 
Published: November 2003

SummaryBacteria are often found associated with surfaces as sessile bacterial communities called biofilms, and the formation of a biofilm can be split up into different stages each requiring the expression of specific genes. The production of extracellular polysaccharides (EPS) is important for the maturation of biofilms and is controlled by the Rcs two‐component pathway in Escherichia coli (and other Gram‐negative bacteria). In this study, we show, for the first time, that the RcsC sensor kinase is required for normal biofilm development in E. coli. Moreover, using a combination of DNA macroarray technology and transcriptional fusion analysis, we show that the expression of > 150 genes is controlled by RcsC in E. coli. In silico analyses of the RcsC regulon predicts that 50% of the genes encode proteins that are either localized to the envelope of E. coli or have activities that affect the structure/properties of the bacterial surface, e.g. the production of colanic acid. Moreover, we also show that RcsC is activated during growth on a solid surface. Therefore, we suggest that the RcsC sensor kinase may play an important role in the remodelling of the bacterial surface during growth on a solid surface and biofilm formation.
IDENTIFYING MUSCULOSKELETAL CONDITIONS AMONG RURAL INDIGENOUS PEOPLES
Authors: Vindigni Dein , Perkins Janice 
Published: November 2003

ABSTRACTObjective: To critically review the methodological properties of previous musculoskeletal studies among Indigenous populations. In particular, non‐rheumatic, musculoskeletal conditions of mechanical origin are examined as these appear to be commonly related to syndromes of pain and disability.Design: Systematic review.Setting: Rural, Indigenous communities throughout the world.Subjects: Indigenous peoples aged 16 and over living in rural communities.Main outcome measure: Minimum requirements for methodologically sound musculoskeletal health research according to previously published criteria.Results: Due to methodological limitations in the 14 studies reviewed, only five methodologically acceptable studies were found.Conclusion: Given the paucity of methodologically sound musculoskeletal studies among Indigenous populations, the true prevalence of musculoskeletal conditions in these communities remains largely unknown.
BALANCING HOSPITAL AND COMMUNITY TREATMENT: EFFECTIVENESS OF AN EXTENDED‐HOURS COMMUNITY MENTAL HEALTH TEAM IN A SEMI‐RURAL REGION OF AUSTRALIA
Authors: Habibis Daphne , Hazelton Mike , Schneider Rosemary , Davidson John , Bowling Alison 
Published: November 2003

ABSTRACTObjective: To examine the effectiveness of the introduction of a community mental health team on consumer psychosocial outcomes.Design: Longitudinal panel design.Setting: District general hospital in a semi‐rural region of Australia.Numbers: Two matched groups (n = 37 in each group)Main outcome measure: These included: Brief Psychiatric Rating Scale (BPRS), Global Assessment Scale (GAS), Rosenberg Self‐Esteem, Life Skills Profile as well as self‐report.Results: The study found that the introduction of the new service resulted in few significant differences in consumer outcomes.Conclusions: The paper argues that because the state was the only specialist mental health service provider and it was unable to offer assertive community treatment, hospital care remained central. Evidence that a substantial proportion of consumers and carers preferred hospital to community care is placed against this background. The paper argues that in regions like these, where community‐based services are likely to remain underdeveloped, it may be best to maintain quality hospital services and to target community services more precisely on what is achievable rather than developing community services at the expense of hospital care.What is already known: Studies on the efficacy of assertive community treatment suggest that it can lead to improved consumer outcomes. However, these studies are usually in urban settings and involve experimental teams. In many rural and regional areas community treatment teams offer standard rather than assertive community care. It is therefore important to investigate the effectiveness of community treatment teams in rural and regional Australia.What this study adds: This study suggests that in rural and regional areas characterised by limited resources, it is too much to expect community treatment teams to have a measurable impact on consumer outcomes. In these settings hospital care remains at the heart of the service. This means that regions such as these need to focus their community services on what is achievable given the level of resources and social ecology. For example, they may need to consider offering either crisis intervention or rehabilitation services and to rely on innovations, such as telehealth or strategic alliances with other service providers to fill the gap.
Effects of losartan on pressure overload‐induced cardiac gene expression profiling in rats
Authors: Li Jinliang , Li Ping , Feng Xinheng , Li Zhaoping , Hou Rong , Han Chide , Zhang Youyi 
Published: November 2003

Summary1. In the present study, the effects of losartan on myocardial gene expression changes following cardiac hypertrophy were investigated.2. Male Wistar rats were randomized to receive 5 or 30 mg/kg per day losartan (i.p.) 1 day after suprarenal abdominal aortic constriction. Two weeks later, cardiac morphology and function were recorded with echocardiography and mean arterial central pressure was measured using carotid catheters. Myocardial gene expression was assessed with cDNA microarrays.3. The ratios of left ventricular weights to bodyweights, the posterior thickness of the left ventricle and mean arterial central pressure were significantly increased by aortic constriction and attenuated by losartan in a dose‐related manner. Genes in different functional categories were regulated in pressure overload‐induced cardiac hypertrophy and the majority of changes in gene expression were inhibited by losartan in a dose‐dependent manner.4. However, there were still some genes that were unaffected by losartan, even at a higher dose. In contrast, losartan, especially at a lower dose, was able to induce changes in the expression of several additional genes that were unregulated in simple aortic constriction.5. In conclusion, losartan is able to inhibit pressure overload‐induced cardiac hypertrophy, as well as the majority of pressure overload‐related changes in gene expression. The genes that remained unaffected or those that were additionally induced by losartan are likely to be new targets for investigation or therapy.