bluuebunny/crossref_metadata_2025 huggingface dataset:
Association analysis of the RGS4 gene in Han Chinese and Scottish populations with schizophrenia
Authors: Zhang F. , St Clair D. , Liu X. , Sun X. , Sham P. C. , Crombie C. , Ma X. , Wang Q. , Meng H. , Deng W. , Yates P. , Hu X. , Walker N. , Murray R. M. , Collier D. A. , Li T.
Published: September 2005

We investigated the RGS4 as a susceptibility gene for schizophrenia in Chinese Han (184 trios and 138 sibling pairs, a total of 322 families) and Scottish (580 cases and 620 controls) populations using both a family trio and case‐control design. Both the samples had statistical power greater than 70% to detect a heterozygote genotype relative risk of >1.2 for frequent RGS4‐risk alleles. We genotyped four single nucleotide polymorphisms (SNPs) which have previously been associated with schizophrenia as either individually or part of haplotypes. Allele frequencies and linkage disequilibrium between the SNPs was similar in the two populations. In the Chinese sample, no individual SNPs or any of their haplotypes were associated with schizophrenia. In the Scottish population, one SNP (SNP7) was significantly over‐represented in the cases compared with the controls (0.44 vs. 0.38; A allele; χ2 7.08, P = 0.011 after correction for correlation between markers by permutation testing). One two‐marker haplotype, composed of alleles T and A of SNP4 and SNP7, respectively, showed individual significance after correction by permutation testing (χ2 6.8; P = 0.04). None of the full four‐marker haplotypes showed association, including the G‐G‐G‐G haplotype previously associated with schizophrenia in more than one sample and the A‐T‐A‐A haplotype. Thus, our data do not directly replicate previous associations of RGS4, but association with SNP 7 in the Scottish population provides some support for a role in schizophrenia susceptibility. We cannot conclusively exclude RGS4, as associated haplotypes are likely to be surrogates for unknown causative alleles, whose relationship with overlying haplotypes may differ between the population groups. Differences in the association seen across the two populations could result from methodological factors such as diagnostic differences but most likely result from ethnic differences in haplotype structures within RGS4.
Banking on Families: How Families Generate and Distribute Social Capital
Authors: Furstenberg Frank F.
Published: September 2005

Before we can determine the relevance of social capital to the sociology of family and kinship, we must fill the gaps in our theoretical knowledge. For example, we still do not know how couples, parents, children, and groups generate, accumulate, manage, and deploy social capital. Neither do we know the consequences of social capital for the welfare of families and their individual members. To investigate these areas, we must replace the makeshift measures currently in use with measures that do not confuse social capital with the presumed consequences of access to same. With this attention to theoretical elaboration and careful measurement, we will discover whether the idea of social capital is fruitful or merely decorative.
Grounded Theory Methods and Qualitative Family Research
Authors: LaRossa Ralph
Published: September 2005

There is an irony—perhaps a paradox—here: that a methodology that is based on “interpretation” should itself prove so hard to interpret. (Dey, 1999, p. 23)

Among the different qualitative approaches that may be relied upon in family theorizing, grounded theory methods (GTM), developed by Barney Glaser and Anselm Strauss, are the most popular. Despite their centrality to family studies and to other fields, however, GTM can be opaque and confusing. Believing that simplifying GTM would allow them to be used to greater effect, I rely on 5 principles to interpret 3 major phases in GTM coding: open, axial, and selective. The history of GTM establishes a foundation for the interpretation, whereas recognition of the dialectic between induction and deduction underscores the importance of incorporating constructivism in GTM thinking. My goal is to propose a methodologically condensed but still comprehensive interpretation of GTM, an interpretation that researchers hopefully will find easy to understand and employ.
Studying Individual and Family Development: Linking Theory and Research
Authors: O'Brien Marion
Published: September 2005

The predominant theoretical orientation of the majority of scientists studying human behavioral development and family functioning is derived from systems models. These theories are dynamic in their conceptualization and emphasize process and context. To a large extent, the analytic strategies we employ are not consistent with our theoretical assumptions. Analytic methods that focus on moderating and mediating processes rather than main effects, on within‐group variability and the sources of that variability, and on the identification of interrelated patterns of change in individuals, families, and environments are needed for our research results to mirror the complexity of our theories.
Utility of Hospital Emergency Department Data for Studying Intimate Partner Violence
Authors: Saltzman Linda E. , Mahendra Reshma R. , Ikeda Robin M. , Ingram Eben M.
Published: September 2005

The authors examine 12 months of emergency department visit data (N= 2,521) from the National Electronic Injury Surveillance System All Injury Program and explore its utility for measuring and studying intimate partner violence. Given the dearth of national data on intimate partner violence–related injury and its potential value for public health surveillance and prevention, the data set appears promising for estimating national rates of emergency department visits. Missing perpetrator‐patient relationship data limit estimation of intimate partner–related hospital visits for injury and pain, which precludes national rate estimation at this time, but the data are still useful for describing documented intimate partner violence cases and may be helpful in designing prevention strategies.
Measures for Studying Poverty in Family and Child Research
Authors: Roosa Mark W. , Deng Shiying , Nair Rajni L. , Lockhart Burrell Ginger
Published: September 2005

Most family scholars take the concept of poverty for granted. The variety of ways people have chosen to define and measure this concept, however, often makes it difficult to interpret or compare research results. We review and critique the ways that poverty has been measured in the family and child literatures as well as the measures that have been used to help understand variations in adaptation among those in poverty. In addition to reviewing more common measures, we include discussions of two new measures that have the potential to contribute to the literature on poverty: basic family budgets and social exclusion.
Measuring Intergenerational Obligations
Authors: Ganong Lawrence , Coleman Marilyn
Published: September 2005

Researchers have defined intergenerational obligations in diverse ways, and they have used many labels and ways of measuring intergenerational obligations. Using vignettes, we compared responses to questions about what family members should do when another family member needed assistance (normative obligations) with responses to questions about what respondents would do if they were in the situation in the vignette (felt responsibilities). Felt and normative obligations were similar. When there were disagreements, respondents indicated they would help more than they thought the character in the vignette should. The results point to the need for researchers to clearly define their terms, and they must carefully select operational definitions that match the conceptual definitions used when studying obligations about intergenerational assistance.
Working With Missing Values
Authors: Acock Alan C.
Published: September 2005

Less than optimum strategies for missing values can produce biased estimates, distorted statistical power, and invalid conclusions. After reviewing traditional approaches (listwise, pairwise, and mean substitution), selected alternatives are covered including single imputation, multiple imputation, and full information maximum likelihood estimation. The effects of missing values are illustrated for a linear model, and a series of recommendations is provided. When missing values cannot be avoided, multiple imputation and full information methods offer substantial improvements over traditional approaches. Selected results using SPSS, NORM, Stata (mvis/micombine), and Mplusare included as is a table of available software and an appendix with examples of programs for Stata and Mplus.
Generalized Linear Models in Family Studies
Authors: WU Zheng
Published: September 2005

Generalized linear models (GLMs), as defined byJ. A. Nelder and R. W. M. Wedderburn (1972), unify a class of regression models for categorical, discrete, and continuous response variables. As an extension of classical linear models, GLMs provide a common body of theory and methodology for some seemingly unrelated models and procedures, such as the logistic, Poisson, and probit models, that are increasingly used in family studies. This article provides an overview of the principle and the key components of GLMs, such as the exponential family of distributions, the linear predictor, and the link function. To illustrate the application of GLMs, this article uses Canadian national survey data to build an example focusing on the number of close friends among older adults. The article concludes with a discussion of the strengths and weaknesses of GLMs.
Effect of Tetrandrine on Calcium‐Dependent Tumour Necrosis Factor‐α Production in Glia‐Neurone Mixed Cultures
Authors: Wang Bin , Yang Li , Yan Hong‐Li , Wang Meng , Xiao Ji‐Gao
Published: September 2005

Abstract: Tumour necrosis factor‐α is believed to have a deleterious role in the pathophysiology of brain injury. Tetrandrine has protective effect on neuronal cells, however, the mechanisms involved in its action have not been clearly established. The aim of this study was to investigate the role of tetrandrine on calcium‐dependent tumour necrosis factor‐α production in glia‐neurone mixed cultures. Glia‐neurone mixed cultures were treated by addition of Ca2+ regulating agents for a period of 6 hr. Tetrandrine or/and TMB‐8 were added 30 min. before the stimulation. The supernatant tumour necrosis factor‐α levels were quantified by enzyme‐linked immunosorbent assay. Exposure of lipopolysaccharide 10 and 100 ng/ml caused significant increase in tumour necrosis factor‐α production respectively, with no alteration in cultures treated with 1 ng/ml lipopolysaccharide. Glia‐neurone mixed cultures exhibited a marked elevation in tumour necrosis factor‐α production after exposure to CaCl2, KCl, thapsigargin, BHQ and norepinephrine in the presence of lipopolysaccharide at 1 ng/ml respectively. Tetrandrine 0.3, 1, and 3 μM concentration‐dependently reduced tumour necrosis factor‐α production evoked by CaCl2 or KCl. Tetrandrine preincubation had no significant effect on the response to Ca2+‐ATPase inhibitor thapsigargin or BHQ. Norepinephrine‐induced tumour necrosis factor‐α production was significantly reduced by tetrandrine and almost abolished by combination of tetrandrine and intracellular Ca2+ release inhibitor TMB‐8. These results suggested that tetrandrine at a concentration of 0.3, 1, or 3 μM inhibited tumour necrosis factor‐α production induced by Ca2+ entry in glia‐neurone mixed cultures.
Chronic Administration of Nandrolone Decanoate Does Not Increase the Plasma Homocysteine Level of Male Rats
Authors: Mirkhani Hossein , Golbahar Jamal , Shokri Saeed
Published: September 2005

Abstract:Androgenic‐anabolic steroids are used widely by many athletes in order to increase muscle mass and strength. Since plasma total homocysteine, an independent risk factor of vascular diseases, is higher in men than in women, it has been proposed that androgenic hormones could increase the plasma total homocysteine level and it might play some role in sudden death when used at supraphysiological doses. To study the association between the use of androgenic‐anabolic steroids and plasma homocysteine level, nandrolone decanoate was administered in 3 and 10 mg/kg doses to male rats by intramuscular weekly injections. Control animals received the solvent of nandrolone decanoate. After 14 weeks, plasma total homocysteine level was measured. In order to make sure about the adequacy of doses and bioavailability of drug, testes parameters were also considered. While all testes parameters were suppressed significantly, no association between androgenic‐anabolic steroids use and total homocysteine level was found.It is concluded that chronic administration of nandrolone decanoate does not have any significant effect on plasma total homocysteine of male rats. Thus, factors other than plasma total homocysteine level may contribute to increased cardiovascular events after chronic abuse of androgenic‐anabolic steroids.
Effect of Thioperamide on Modified Forced Swimming Test‐Induced Oxidative Stress in Mice
Authors: Akhtar Mohd. , Pillai K. K. , Vohora Divya
Published: September 2005

Abstract: This study was designed i) to investigate the role of histamine H3‐receptor ligands on mouse modified forced swimming test, a method that distinguishes the catecholaminergic behaviour with that of serotonergic compounds and ii) to evaluate the role of free radicals in mediation of such effects. Swiss strain albino mice were treated with different doses of histamine H3‐receptor antagonist thioperamide (3.75, 7.5 and 15 mg/kg intraperitoneally) and agonist (R)‐α‐methylhistamine (5 μg intracerebroventricularly). The climbing, swimming and immobility times were recorded for 6 min. Immediately after modified forced swimming test, the animals were sacrificed and parameters of oxidative stress were assessed in the brain by measuring the thiobarbituric acid reactive substance (TBARS), glutathione (GSH) and catalase levels. Thioperamide (7.5 and 15 mg/kg intraperitoneally) dose‐dependently decreased immobility time and increased swimming time but not climbing time. The behaviour of mice treated with (R)‐α‐methylhistamine was similar to that of control mice. A significant reduction in GSH and an increase in catalase levels were observed in brains of mice exposed to modified forced swimming test. Thioperamide pretreatment dose‐dependently reversed such an alteration in oxidative stress parameters. (R)‐α‐methylhistamine caused a reversal of altered catalase but not GSH levels. Thioperamide shows antidepressant effects in the modified forced swimming test and causes a reversal of the test‐induced oxidative stress indicating its antioxidant potential. The antidepressant effect of thioperamide appears to be mediated via serotonergic and/or antioxidant mechanisms.
1H Nuclear Magnetic Resonance Spectroscopic Investigation of Urine for Diagnostic and Clinical Assessment of Methanol Intoxication
Authors: Janus Tomasz , Borowiak Krzysztof S. , Pabisiak Krzysztof , Machoy‐Mokrzyńska Anna , Świniarski Andrzej , Rozwadowski Zbigniew
Published: September 2005

Abstract: Occasional or suicidal methanol intoxications are a permanent problem for most Poisoning Centers around the World. Therefore it is important to look for new diagnostic and clinical prognostic methods. In the present paper 5 cases of methanol intoxication were analyzed. At first the methanol concentrations in blood and urine were estimated with headspace gas chromatography technique. Next the urine samples were examined with 1H NMR spectroscopy, then the levels of ethanol, methanol and its metabolite, formate, lactate and trimethylamine‐N‐oxide with dimethylamine were evaluated. The concentrations of the above compounds were correlated with the patient's clinical status, the level of ethanol and methanol and biochemical parameters. The results indicate the correlation between clinical course of intoxication, prognostication and lactate level. There were no significant parallels for formate level as acidosis causing metabolite and initial methanol levels. In the urine samples of intoxicated patients the increased trimethyl‐N‐oxide and dimethylamine levels were observed, which may indicate renal cortex damage. Contrary to the opinion of some clinicians, methanol intoxication may be connected with renal functional disturbances. 1H NMR examination of urine appears to be an excellent tool to evaluate the clinical course of methanol intoxication.
Metabolism of Repaglinide by CYP2C8 and CYP3A4 in vitro: Effect of Fibrates and Rifampicin
Authors: Kajosaari Lauri I. , Laitila Jouko , Neuvonen Pertti J. , Backman Janne T.
Published: September 2005

Abstract: Repaglinide is an antidiabetic drug metabolised by cytochrome P450 (CYP) 2C8 and CYP3A4 enzymes. To clarify the mechanisms of observed repaglinide drug interactions, we determined the contribution of the two enzymes to repaglinide metabolism at different substrate concentrations, and examined the effect of fibrates and rifampicin on CYP2C8, CYP3A4 and repaglinide metabolism in vitro. We studied repaglinide metabolism using pooled human liver microsomes, recombinant CYP2C8 and recombinant CYP3A4 enzymes. The effect of quercetin and itraconazole on repaglinide metabolism, and of gemfibrozil, bezafibrate, fenofibrate and rifampicin on CYP2C8 (paclitaxel 6α‐hydroxylation) and CYP3A4 (midazolam 1‐hydroxylation) activities and repaglinide metabolism were studied using human liver microsomes. At therapeutic repaglinide concentrations (<0.4 μM), CYP2C8 and CYP3A4 metabolised repaglinide at similar rates. Quercetin (25 μM) and itraconazole (3 μM) inhibited the metabolism of 0.2 μM repaglinide by 58% and 71%, and that of 2 μM repaglinide by 56% and 59%, respectively. The three fibrates inhibited CYP2C8 (Ki: bezafibrate 9.7 μM, gemfibrozil 30.4 μM and fenofibrate 92.6 μM) and repaglinide metabolism (IC50: bezafibrate 37.7 μM, gemfibrozil 111 μM and fenofibrate 164 μM), but had no effect on CYP3A4. Rifampicin inhibited CYP2C8 (Ki 30.2 μM), CYP3A4 (Ki 18.5 μM) and repaglinide metabolism (IC50 13.7 μM). In conclusion, both CYP2C8 and CYP3A4 are important in the metabolism of therapeutic concentrations of repaglinide in vitro, but their predicted contributions in vivo are highly dependent on the scaling factor used. Gemfibrozil is only a moderate inhibitor of CYP2C8 and does not inhibit CYP3A4; inhibition of CYP‐enzymes by parent gemfibrozil alone does not explain its interaction with repaglinide in vivo. Rifampicin competitively inhibits both CYP2C8 and CYP3A4, which can counteract its inducing effect in humans.
Thermodynamic and Economic Investigation of an Improved Graz Cycle Power Plant for CO2 Capture
Authors: Sanz Wolfgang , Jericha Herbert , Moser Mathias , Heitmeir Franz
Published: September 2005

Introduction of closed-cycle gas turbines with their capability of retaining combustion generated CO2 can offer a valuable contribution to the Kyoto goal and to future power generation. Therefore, research and development at Graz University of Technology since the 1990s has lead to the Graz Cycle, a zero emission power cycle of highest efficiency. It burns fossil fuels with pure oxygen, which enables the cost-effective separation of the combustion CO2 by condensation. The efforts for the oxygen supply in an air separation plant are partly compensated by cycle efficiencies far higher than 60%. In this work a further development, the S-Graz Cycle, which works with a cycle fluid of high steam content, is presented. Thermodynamic investigations show efficiencies up to 70% and a net efficiency of 60%, including the oxygen supply. For a 100 MW prototype plant the layout of the main turbomachinery is performed to show the feasibility of all components. Finally, an economic analysis of a S-Graz Cycle power plant is performed showing very low CO2 mitigation costs in the range of $10/ton CO2 captured, making this zero emission power plant a promising technology in the case of a future CO2 tax.
Coupled Simulations of Nozzle Flow, Primary Fuel Jet Breakup, and Spray Formation
Authors: von Berg Eberhard , Edelbauer Wilfried , Alajbegovic Ales , Tatschl Reinhard , Volmajer Martin , Kegl Breda , Ganippa Lionel C.
Published: September 2005

Presented are two approaches for coupled simulations of the injector flow with spray formation. In the first approach the two-fluid model is used within the injector for the cavitating flow. A primary breakup model is then applied at the nozzle orifice where it is coupled with the standard discrete droplet model. In the second approach the Eulerian multi-fluid model is applied for both the nozzle and spray regions. The developed primary breakup model, used in both approaches, is based on locally resolved properties of the cavitating nozzle flow across the orifice cross section. The model provides the initial droplet size and velocity distribution for the droplet parcels released from the surface of a coherent liquid core. The major feature of the predictions obtained with the model is a remarkable asymmetry of the spray. This asymmetry is in agreement with the recent observations at Chalmers University where they performed experiments using a transparent model scaled-up injector. The described model has been implemented into AVL FIRE computational fluid dynamics code which was used to obtain all the presented results.
Modeling Oil Flows on Seal Runners and Engine Sump Walls
Authors: Shimo Masayoshi , Canino James V. , Heister Stephen D.
Published: September 2005

Oil flow behavior within a lubrication system utilized in a turbofan engine has been studied using a two-dimensional model for a seal runner and a sump wall. A two-dimensional, axisymmetric boundary layer method is utilized to derive a model for the film on the seal runner. An integral method analysis of boundary layer equations are utilized to derive a model for the film behavior on the outer wall of the sump neglecting variations in the axial direction. Parametric studies for oil flow at the seal runner and one the sump wall have been generated for a wide range of oil film properties and ambient conditions.
Sensitivity of Tuned Bladed Disk Response to Frequency Veering
Authors: Kenyon J. A. , Griffin J. H. , Kim N. E.
Published: September 2005

A continuous method is presented for representing the mode interaction that occurs in frequency veering in terms of the nominal sector modes of a cyclic symmetric bladed disk model constrained at a reference interblade phase angle. Using this method, the effect of frequency veering on the mode shapes can be considered in the context of the generalized forces exciting the system and the modal response of the bladed disk. It is shown that in a blade-dominated family of modes, the transfer of modal energy to the disk in the veering results in a lower generalized force exciting the mode as well as reduced response amplitude in the blade. For the disk-dominated modes, the sharing of modal energy with the blades can lead to the disk being excited by aerodynamic loading. These effects can have important implications for predicting and interpreting forced response in bladed disks. Numerical examples are provided to illustrate these concepts.
Rotordynamic Coefficients for a Tooth-on-Stator Labyrinth Seal at 70 Bar Supply Pressures: Measurements Versus Theory and Comparisons to a Hole-Pattern Stator Seal
Authors: Picardo Arthur , Childs Dara W.
Published: September 2005

Rotor dynamic and leakage coefficients are presented for a labyrinth seal that was tested at a supply pressure of 70 bar-a and speeds up to 20,200 rpm. Tests were conducted at clearances of 0.1 mm and 0.2 mm, pressure ratios of 0.10, 0.31, and 0.52, and three preswirls ratios. Comparisons are made between test data and predictions from one-control-volume and two-control-volume bulk-flow models. Generally, theoretical predictions agree poorly with the test results, with the one-control volume model giving better predictions. The one-control-volume model provides a conservative prediction for effective damping; i.e., this parameter is underestimated. Both models under predict leakage rates. Comparisons are also made between rotordynamic coefficients of labyrinth and hole-pattern seals.
Comparison of Computational Fluid Dynamics and Particle Image Velocimetry Data for the Airflow in an Aeroengine Bearing Chamber
Authors: Lee C. W. , Palma P. C. , Simmons K. , Pickering S. J.
Published: September 2005

Investigations into the single-phase velocity field of a model aeroengine bearing chamber are presented. Adequately resolving the airflow field is important to subsequent computational modeling of two-phase fluid transport and heat transfer characteristics. A specially designed test rig, representing the features of a Rolls Royce Trent series aeroengine bearing chamber, was constructed. Experimental data for the airflow field was obtained using particle image velocimetry (PIV). The results show a strong influence of shaft rotation and chamber geometry on the flow features within the bearing chamber. A computational fluid dynamics (CFD) simulation was carried out using the commercial CFD code FLUENT 6. Flow features were adequately modeled, showing the features of secondary velocities. Turbulence modeling using the differential Reynolds stress (RSM) model shows good agreement with the experimental data.
Active Instability Control: Feedback of Combustion Instabilities on the Injection of Gaseous Fuel
Authors: Auer M. P. , Gebauer C. , Mösl K. G. , Hirsch C. , Sattelmayer T.
Published: September 2005

Modern low-emission premix combustion systems are often susceptible to combustion instabilities. Active instability control (AIC) systems are commonly used to attenuate these oscillations. For the control authority of AIC systems the effective amplitude and phase of the fuel modulation at the fuel outlet are as critical as the proper injection position. In typical cases the modulation of the fuel at the location of the actuator can be fundamentally different in amplitude and phase from the modulation of the fuel flow at the fuel outlet. In addition to the well-known effects stemming from the acoustics and Mach number of the fuel system, the fuel flow in the fuel system is also modulated by the oscillation of the pressure in the combustor in case of combustion instabilities. The superposition of the upstream modulation by the actuator and the modulation downstream by the combustion instability can result in an unexpected behavior of the fuel injection, from total compensation of the modulation to very high oscillations in the resonant case, accompanied by drastic phase shifts. This paper describes the influence of the secondary fuel modulation because of the combustion instability on the control authority of AIC systems on the basis of theoretical considerations and measurements for an atmospheric test rig with a natural gas-fired swirl burner.
Characterization of Turbine Blade Friction Dampers
Authors: Koh K.-H. , Griffin J. H. , Filippi S. , Akay A.
Published: September 2005

This paper discusses an approach for characterizing the dynamic behavior of a friction damper. To accomplish this, the deflection of the damper is measured as a function of an applied force for a range of amplitudes, normal loads, and excitation frequencies. The resulting hysteresis curves are used to generate curves of nonlinear stiffness and damping as a function of the amplitude of motion. A method of presenting this information in a dimensionless format is demonstrated. This format allows direct comparisons of the nonlinear stiffness and damping of actual dampers with that often used in analytical models to compute the dynamic response of frictionally damped turbine blades. It is shown that for the case of a damper with a spherical head significant differences exist between the actual behavior of the damper and that often assumed in simple analytical models. In addition, Mindlin’s analysis of a sphere on a half space is used to estimate the damper’s stiffness as well as its theoretical hysteresis curves. The hysteresis curves are then used to determine dimensionless stiffness and damping curves. The results compare favorably with those found experimentally.
Regulation of the expression of photorespiratory genes inChlamydomonas reinhardtii
Authors: Tural Baran , Moroney James V
Published: September 2005

The regulation of the photorespiratory pathway in Chlamydomonas reinhardtii Dangeard during a shift from high- to low-CO2conditions was investigated. To this end, a set of C. reinhardtii cDNA sequences for known photorespiratory enzymes was assembled using the Chlamydomonas expressed sequence tag database and primary sequencing data. Expression data indicates that there is a rapid and coordinated induction of photorespiratory and CCM gene expression during a time course switch from high-CO2conditions (5% (v/v)) to low-CO2conditions (0.038% (v/v)). While the expression of photorespiratory and CCM genes are coordinated during the initial change in CO2level, the response of these two sets of genes to the CO2level is not identical. Unlike the sustained high levels of CCM mRNAs seen under low CO2conditions, photorespiratory mRNAs show a transient increase in abundance in time course experiments. In addition, the expression of these photorespiratory genes is reduced in cia5, a C. reinhardtii strain that lacks a transcription factor required for the induction of genes involved in the CO2-concentrating mechanism. From these observations, there appears to be coordination in the expression of the genes involved in the delivery of CO2to Rubisco and the genes involved in the metabolism of the photorespiratory products that form when the CO2level is low.Key words: Chlamydomonas reinhardtii, photorespiratory genes, gene expression, CO2-concentrating mechanism.
Disruption of the glycolate dehydrogenase gene in the high-CO2-requiring mutant HCR89 ofChlamydomonas reinhardtii
Authors: Nakamura Yoshiko , Kanakagiri Saradadevi , Van Kyujung , He Wei , Spalding Martin H
Published: September 2005

One of the most notable contrasts between the photorespiratory pathway of higher plants and that of many of the green algae including Chlamydomonas reinhardtii lies in the enzymes that serve for oxidation of glycolate to glyoxylate. The gene disrupted by insertional mutagenesis in a high-CO2-requiring mutant, HCR89, of C. reinhardtii was determined to encode glycolate dehydrogenase (EC 1.1.99.14), which serves as the counterpart of glycolate oxidase (EC 1.1.3.15) in classical higher plant photorespiration. Neither glycolate nor D-lactate oxidation from the membrane fraction of HCR89 was detected. Excretion of over-accumulated glycolate into media due to the absence of glycolate dehydrogenase activity was observed for HCR89 under both high- and low-CO2conditions. Chlamydomonas glycolate dehydrogenase, CrGDH, with a molecular mass of 118 851 Da, comprises a relatively hydrophobic N-terminal region, a FAD-containing domain homologous to the D subunit of the glycolate oxidase complex from Escherischia coli, and an ironsulfur cluster containing domain homologous to the C subunit of anaerobic glycerol-3-phosphate dehydrogenase complex from Escherichia coli. The second Cys residue in the second ironsulfur cluster motif of CrGDH is replaced by Asp, as CxxDxxCxxxCP, indicating the second ironsulfur cluster coordinates most likely 3Fe4S instead of 4Fe4S. The membrane association of the glycolate dehydrogenase activity agrees with three predicted transmembrane regions on the ironsulfur domain.Key words: algae, Chlamydomonas, CO2, glycolate, lactate, mitochondria, photorespiration, photosynthesis.
Carbon acquisition mechanisms by planktonic desmids and their link to ecological distribution
Authors: Spijkerman Elly , Maberly Stephen C , Coesel Peter FM
Published: September 2005

To test if different inorganic carbon (Ci) uptake mechanisms underlie the ecological distribution pattern of planktonic desmids, we performed pH-drift experiments with 12 strains, belonging to seven species, originating from lakes of different pH. Staurastrum brachiatum Ralfs and Staurodesmus cuspidatus (Ralfs) Teil. var. curvatus (W. West) Teil., species confined to acidic, soft water habitats, showed remarkably different behavior in the pH drift experiments: S. brachiatum appeared to use CO2 only, whereas Staurodesmus cuspidatus appeared to use HCO3 as well. Staurastrum chaetoceras (Schr.) Smith and Staurastrum planctonicum Teil, species well-known for their abundant occurrence in alkaline waters, were the most effective at using HCO3. Other species, to be encountered in both slightly acidic and slightly alkaline waters, took an intermediate position. Experiments using specific inhibitors suggested that Cosmarium abbreviatum Rac. var. planctonicum W. & G.S. West and S. brachiatum use CO2 by an active CO2 uptake mechanism, whereas S. chaetoceras and Staurodesmus cuspidatus showed an active HCO3 uptake pattern. Most likely, these active uptake mechanisms make use of H+-ATPase, as none of the desmids expressed significant carbonic anhydrase activity. A series of strains of Staurastrum planctonicum isolated from different habitats, all clustered in between the species using HCO3, but no further differentiation was observed. Therefore, desmids cannot be simply characterized as exclusive CO2 users, and the ecological distribution pattern of a desmid species does not unequivocally link to a certain Ci uptake mechanism. Nevertheless, there does appear to be a general ecological link between a species' Ci uptake mechanism and its ecological distribution.Key words: pH drift, desmids, isolate variation, inorganic carbon acquisition.
The phosphoglycolate phosphatase gene and the mutation in the phosphoglycolate phosphatase-deficient mutant (pgp1-1) ofChlamydomonas reinhardtii
Authors: Suzuki Kensaku , Uchida Hidenobu , Mamedov Tarlan G
Published: September 2005

The sequences of the phosphoglycolate phosphatase (PGPase) gene Pgp1 and the 5′-upstream region from Chlamydomonas reinhardtii wildtype 2137 and the pgp1-1 mutant N142 that lacks the activity of PGPase (PGP1) were determined. The comparison revealed the alteration of a G to A at position 98 relative to the start codon. This destroyed the "GT" splice donor site at the beginning of the first intron of this gene, resulting in an extension of the first exon to 49 translatable codons followed by a stop codon, containing the codons corresponding to whole transit peptide for the chloroplast stroma and the first four N-terminal amino-acid residues of the PGP1 subunit. The comparison of the upstream nucleotide sequence of Pgp1 with those of 37 other genes including those involved in the CO2-concentrating mechanism and (or) photorespiration showed the high similarity of Pgp1 upstream to a periplasmic carbonic anhydrase gene Cah1; the motifs RAGGTCAGN8-9CCR and TTGGCAG were found only within the low-CO2responsive genes, including Pgp1 and Cah1. GAN7CGNTTGGAAN2AG, TTGGAAGGAG, and CAGAGGTCAGN8CCG were found only with Pgp1 and Cah1, and ACGCTTGGCAGT and CATTACCAT were found only with Pgp1 and alanine aminotransferase gene Aat1. The possibility of functional PGPase isozyme(s) in C. reinhardtii is also discussed.Key words: Chlamydomonas reinhardtii, CO2-concentrating mechanism, low-CO2responsive gene, pgp1-1 mutation, phosphoglycolate phosphatase.
Algae lacking carbon-concentrating mechanisms
Authors: Raven John A , Ball Lucy A , Beardall John , Giordano Mario , Maberly Stephen C
Published: September 2005

Most of the algae and cyanobacteria that have been critically examined express a carbon-concentrating mechanism (CCM) when grown at, or below, the current atmospheric CO2 concentration. This paper considers algae that appear to lack a CCM. Critical examination of the evidence on which the presence or absence of a CCM is decided shows that more information is frequently needed before the criteria can be fully applied. Examples are the pathways of glycolate metabolism in nongreen algae, and the 13C/12C discrimination shown by form ID Rubisco in vitro. The available evidence suggests that the algae lacking CCMs are some terrestrial green microalgae, some florideophyte freshwater red macroalgae, and a number of florideophyte red macroalgae from the supralittoral, littoral, and sublittoral, and almost all of the freshwater chrysophytes and synurophytes examined. Certain environmental, biochemical, and biophysical factors may permit the occurrence of algae lacking CCMs. The absence of CCMs is presumably the plesiomorphic (i.e., ancestral) condition in cyanobacteria (and algae?).Key words: CO2 diffusion, chrysophyte algae, ecology, evolution, green algae, photosynthesis, red algae.
How do marine diatoms fix 10 billion tonnes of inorganic carbon per year?
Authors: Granum Espen , Raven John A , Leegood Richard C
Published: September 2005

Diatoms are responsible for at least a quarter of inorganic carbon fixed each year in the ocean. Despite very considerable research over the last 30 years, there are still a number of fundamental unresolved aspects of inorganic carbon assimilation by marine diatoms. It is not clear how the carbon-concentrating mechanism functions and whether it is based on the direct acquisition of inorganic carbon or on a C4pathway, or a combination of both. Although evidence for the operation of a C4pathway is accumulating, the role(s) of the enzyme(s) responsible for "C3+ C1" inorganic carbon assimilation in the light and dark are still matters of controversy. In this review, we discuss whether diatoms possess the enzymic and structural components necessary for a C4-type CO2-concentrating mechanism. These are compared and contrasted with other C4systems, both single-celled and those in terrestrial plants, which are based on Kranz anatomy. New data are presented on expression of genes that might be involved in C4photosynthesis, including phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxykinase.Key words: CO2-concentrating mechanism, C4photosynthesis, marine diatoms, phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase.
Modulation of photosynthesis and inorganic carbon acquisition in a marine microalga by nitrogen, iron, and light availability
Authors: Young Erica B , Beardall John
Published: September 2005

The marine microalga Dunaliella tertiolecta Butcher expresses a high affinity for dissolved inorganic carbon (DIC) through a carbon-concentrating mechanism (CCM), known to be influenced by CO2 availability and instantaneous light supply. However, the regulation by light and nutrient supply during growth is less understood, although N and Fe limitation impose an energy limitation by compromising the photosynthetic apparatus. Dunaliella tertiolecta was grown under steady-state conditions of limited light, N, and Fe availability, and the affinity for DIC was measured under saturating light. High affinity DIC uptake capacity was maintained by D. tertiolecta under all growth-limiting conditions, but was modulated in response to the limiting resource. Affinity of photosynthesis for DIC(k0.5) was significantly reduced in cells grown under low light, both in turbidostats and in batch culture (p ≤ 0.03), although cell-normalized Pmax was not significantly affected. In contrast, N and Fe limitation resulted in a significant reduction in cell chlorophyll, Pmax, and maximum photosystem II quantum yield (Fv/Fm), but the affinity for DIC was enhanced with increasing N or Fe stress. While the affinity for DIC improved with increasing N stress (k0.5 < 17.8 µM at µ = 0.27 d1 versus k0.5 > 26 µM at µ ≥ 0.77 d1), light use efficiency (α) was impaired under N limitation, suggesting a trade-off between light harvesting capacity and active DIC uptake. Stable C isotope analysis of Fe-limited cells confirmed a lower fractionation by the most Fe-limited cells, consistent with the k0.5 data and more active DIC acquisition (δ13C = 19.56 at µ = 0.27 d1 cf. δ13C = 26.28 at µ = 0.77 d1). Assessment of affinity for DIC using k0.5 was supported by the close fit of P versus DIC curves to MichaelisMenten kinetics; with the high DIC affinity of D. tertiolecta, there was poor resolution in the initial slope of the P versus DIC curve as a parameter of affinity for DIC. Enhanced DIC uptake efficiency under Fe and N limitation may relate to improved resource-use efficiency conferred by CCM activity.Key words: algae, carbon-concentrating mechanism, iron, light, nitrogen, nutrient limitation, photosynthesis.
The influence of phytoplankton biomass on the spatial distribution of carbon dioxide in surface sea water of a coastal area of the Gulf of Cádiz (southwestern Spain)
Authors: Huertas Emma , Navarro Gabriel , Rodríguez-Gálvez Susana , Prieto Laura
Published: September 2005

The spatial variability in carbon dioxide in surface waters of a coastal area of the Gulf of Cádiz (southwestern Spain) was examined in situ under spring bloom conditions. The influence of phytoplankton biomass and physicochemical variables on the CO2 concentration was studied. According to the relationship observed between chlorophyll a and pCO2, phytoplankton biomass was the main factor responsible for variations in carbon dioxide. The distribution of organic matter in the form of dissolved organic carbon and transparent exopolymer particles also reflected changes in phytoplankton abundance, since high levels of both variables were associated with high chlorophyll concentrations and low levels of free CO2. The involvement of the enzyme carbonic anhydrase in the process of inorganic carbon uptake by the phytoplankton community was also investigated through the effect of the inhibitors dextran-bound sulfonamide and ethoxyzolamide on primary production rates. Ethoxyzolamide substantially inhibited carbon fixation, causing decreases of 40%60% in the maximum photosynthetic rates; whereas the membrane impermeable inhibitor dextran-bound sulfonamide affected primary production, depending on the diversity of the phytoplankton species composition. Calculations of CO2 fluxes indicated that the sampled coastal sector of the Gulf of Cádiz behaved as a net sink for atmospheric CO2 at the time of analysis, with an average CO2 absorption of 0.41 mmol·m2·d1.Key words: airsea exchange of CO2, carbonic anhydrase, flow cytometry, Gulf of Cádiz, phytoplankton, transparent exopolymer particles.
Synergic interaction between pomegranate extract and antibiotics against Staphylococcus aureus
Authors: Braga L C , Leite A A.M , Xavier K G.S , Takahashi J A , Bemquerer M P , Chartone-Souza E , Nascimento A M.A
Published: September 2005

We evaluated the interaction between Punica granatum (pomegranate) methanolic extract (PGME) and antibiotics against 30 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA). Susceptibility testing of the isolates to PGME and antibiotics was performed by the broth dilution method. Synergic activity was detected between PGME and the 5 antibiotics tested, chloramphenicol, gentamicin, ampicillin, tetracycline, and oxacillin, ranging from 38% to 73%. For some isolates, PGME did not interfere with the action of any of the antibiotics tested. The bactericidal activity of PGME (0.1 × MIC) in combination with ampicillin (0.5 × MIC) was assessed using chosen isolates by time-kill assays, and they confirmed the synergic activity. Using this combination, cell viability was reduced by 99.9% and 72.5% in MSSA and MRSA populations, respectively. PGME increased the post-antibiotic effect (PAE) of ampicillin from 3 to 7 h. In addition, PGME demonstrated the potential to either inhibit the efflux pump NorA or to enhance the influx of the drug. The detection of in vitro variant colonies of S. aureus resistant to PGME was low and they did not survive. In conclusion, PGME dramatically enhanced the activity of all antibiotics tested, and thus, offers an alternative for the extension of the useful lifetime of these antibiotics.Key words: Staphylococcus aureus, antibiotic-resistance, synergy, NorA, Punica granatum.
The impacts of cyanobacteria on pulp-and-paper wastewater toxicity and biodegradation of wastewater contaminants
Authors: Kirkwood A E , Nalewajko C , Fulthorpe R R
Published: September 2005

This study investigated the effects of cyanobacteria from pulp-and-paper waste-treatment systems on biological toxicity removal and biodegradation of certain wastewater contaminants. In field and batch studies, using the Microtox®assay, cyanobacterial biomass and final wastewater toxicity were significantly correlated. In softwood-based wastewater, a decrease in toxicity was negatively correlated with cyanobacterial biomass, but the correlation was positive in hardwood-based wastewater. In the softwood-based wastewater, toxicity remained higher in the light than it was in the dark, whereas in hardwood-based wastewater, toxicity was lower in the light than it was in the dark. All of these results were light-dependent, suggesting that the photosynthetic growth of cyanobacteria is required to induce significant effects. When grown in mixed cultures with bacterial degraders, cyanobacteria from pulp-and-paper waste-treatment systems generally impeded the biodegradation of the wastewater contaminants phenol and dichloroacetate (DCA). However, there was one case where the cyanobacterium Phormidium insigne improved the bacterial degradation of DCA. Doubling inorganic nutrient concentrations did not improve phenol or DCA biodegradation in the majority of cases, indicating that nutrient competition is not a major factor. These data suggest that cyanobacteria play an important role during the biological treatment of contaminants, and, hence, toxicity removal in pulp-and-paper waste-treatment systems.Key words: cyanobacteria, heterotrophic bacteria, biodegradation, pulp and paper waste-treatment, wastewater toxicity.
The presence of 3-hydroxy oxylipins on the ascospore surfaces of some species representing Saccharomycopsis Schiönning
Authors: Sebolai Olihile M , Kock Johan L.F , Pohl Carolina H , Botes Piet J , Strauss Catharina J , Van Wyk Pieter W.J , Nigam Santosh
Published: September 2005

Through gas chromatography – mass spectrometry, the presence of oxylipins, mainly 3-hydroxy 9:1 and 3-hydroxy 10:1, was detected in Saccharomycopsis fermentans, Saccharomycopsis javanensis, and Saccharomycopsis vini. The distribution of these compounds was mapped using immunofluorescence microscopy, and they were found to be closely associated with the surfaces of aggregating ascospores.Key words: ascospores, gas chromatography – mass spectrometry, 3-hydroxy oxylipins, immunofluorescence microscopy, Saccharomycopsis, yeast.
Biological control of apple blue mold withPseudomonas fluorescens
Authors: Etebarian Hassan-Reza , Sholberg Peter L , Eastwell Kenneth C , Sayler Ronald J
Published: September 2005

Pseudomonas fluorescens isolate 1100-6 was evaluated as a potential biological control agent for apple blue mold caused by Penicillium expansum or Penicillium solitum. Both the wild-type isolate 1100-6 and a genetically modified derivative labeled with the gene encoding the green fluorescent protein (GFP) were compared. The P. fluorescens isolates with or without GFP equally reduced the growth of Penicillium spp. and produced large zones of inhibition in dual culture plate assays. Cell-free metabolites produced by the bacterial antagonists reduced the colony area of Penicillium isolates by 17.3% to 78.5%. The effect of iron chelate on the antagonistic potential of P. fluorescens was also studied. The use of iron chelate did not have a major effect on the antagonistic activity of P. fluorescens. With or without GFP, P. fluorescens significantly reduced the severity and incidence of apple decay by 2 P. expansum isolates after 11 d at 20 °C and by P. expansum and P. solitum after 25 d at 5 °C when the biocontrol agents were applied in wounds 24 or 48 h before challenging with Penicillium spp. Populations of P. fluorescens labeled with the GFP were determined 1, 9, 14, and 20 d after inoculation at 5 °C. The log CFU/mL per wound increased from 6.95 at the time of inoculation to 9.12 CFU/mL (P < 0.05) 25 d after inoculation at 5 °C. The GFP strain did not appear to penetrate deeply into wounds based on digital photographs taken with an inverted fluorescence microscope. These results indicate that P. fluorescens isolate 1100-6 could be an important new biological control for apple blue mold.Key words: Penicillium expansum, P. solitum, postharvest disease, Malus, GFP.