bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of Nitric Oxide Release In Vivo by Ethanol
Authors: Rossetti Zvani L. , Crespi Francesco
Published: November 2004

Objective: Previous studies indicate that the nitric oxide (NO•) pathway is involved in the acute or chronic effects of ethanol on the central nervous system. However, direct evidence for the effect of ethanol on NO• production in vivo is lacking, and it is not clear whether it is inhibition or stimulation of the NO• pathway that contributes to the behavioral effects of ethanol. Herein the release of NO• in the rat striatum in vivo in response to NMDA receptor activation—the dominant mechanism controlling NO• formation–has been investigated after systemic or local injections of ethanol.

Methods: NMDA‐induced release of authentic NO• was measured directly in the striatum of urethane‐anesthetized (1.2 g/kg intraperitoneally) male Sprague‐Dawley rats by using a direct‐current amperometric method coupled to an electrically modified carbon microelectrode. An injector cannula was implanted in the proximity of the electrode (250 μm apart) for focal drugs application.

Results: Local application of NMDA (1 μl, 100 μM) produced a sharp and transient NO• signal. Systemic ethanol, 1 or 2.5 g/kg intraperitoneally, caused a long‐lasting, dose‐dependent inhibition of NMDA‐induced NO• release to 12.2 ± 5.9 and 6.4 ± 3.7% of control, respectively, 60 min after ethanol administration. Dizocilpine (0.5 mg/kg intraperitoneally) mimicked the ethanol effect, inhibiting NO• release to 1.6 ± 0.66% of control. Local application of ethanol (1 μl, 2.5% v/v) in the striatum reduced the NMDA‐induced response to 28.6 ± 3.8% of control. Focal application of the competitive NMDA receptor antagonist d‐(‐)‐2‐amino‐5‐phosphonopentanoic acid (100 μM) or the nonselective NO synthase inhibitor l‐NG‐nitro‐arginine methyl esther (100 μM) also caused inhibition of NMDA‐induced NO• release to 2.4 ± 0.7 and 4.3 ± 0.9% of control, respectively.

Conclusions: Ethanol, at pharmacologically significant doses, strongly inhibits striatal NO• production and release apparently through inhibition of NMDA receptor function. Inhibition of NMDA receptor–mediated activation of the NO• pathway could be a primary neurobiological mechanism contributing to the effects of ethanol.
Enhanced Alcohol Self‐Administration after Intermittent Versus Continuous Alcohol Vapor Exposure
Authors: O'Dell Laura E. , Roberts Amanda J. , Smith Ron T. , Koob George F.
Published: November 2004

Background: Ethanol self‐administering rats exhibit enhanced responding during withdrawal from continuous exposure to ethanol vapor. This study compared self‐administration of ethanol during withdrawal from continuous versus intermittent ethanol vapor.

Methods: Experiment 1 examined self‐administration of ethanol in rats trained to self‐administer ethanol after continuous, intermittent (14 hr on and 10 hr off), or no (i.e., controls) ethanol vapor exposure. Exposure time was equalized such that the intermittent group received 4 weeks of exposure and the continuous group received 2 weeks of exposure. Four self‐administration tests were conducted 2 hr after removal from vapor, and each test was separated by 3 to 4 days of ethanol vapor. Experiment 2 examined self‐administration of ethanol after 2 weeks of intermittent vapor either 2 or 8 hr after removal from vapor. Experiment 3 addressed the specificity of the increased responding for ethanol by examining saccharin self‐administration after 2 weeks of intermittent vapor.

Results: Four weeks of intermittent exposure produced an increase in ethanol self‐administration during the first withdrawal relative to controls and relative to animals receiving 2 weeks of continuous exposure. The continuous group was indistinguishable from controls on the first test and gradually increased their responding across tests. Two weeks of intermittent exposure also increased ethanol self‐administration, and there was no difference in this effect 2 or 8 hr after removal from vapor. There was no difference in saccharin self‐administration in control rats and those given 2 weeks of intermittent exposure.

Conclusions: The finding that intermittent exposure produces more rapid increases in self‐administration of ethanol relative to continuous exposure suggests that intermittent exposure may be associated with a more rapid escalation of the allostatic processes responsible for excessive ethanol self‐administration. The mechanisms that drive the increases in drinking during withdrawal are similar after 2 and 8 hr of withdrawal and seem to be specific to ethanol.
Alcohol Intoxication Impairs Phosphorylation of S6K1 and S6 in Skeletal Muscle Independently of Ethanol Metabolism
Authors: Lang Charles H. , Pruznak Anne M. , Deshpande Nobuko , Palopoli Margaret M. , Frost Robert A. , Vary Thomas C.
Published: November 2004

Background: The purpose of this study was to characterize the ability of alcohol to suppress insulin‐like growth factor (IGF)‐I stimulation of ribosomal S6 kinase 1 (S6K1) and 4E‐BP1 phosphorylation, which are central elements in the signal transduction pathway used to coordinate the protein synthetic response and may contribute to the development of alcoholic myopathy.

Methods: In vivo studies examined the dose and time dependency of the ability of alcohol to impair signal transduction under basal and IGF‐I–stimulated conditions. Additional studies examined the effect of gender, nutritional state, and route of alcohol administration. A separate study determined the direct effects of alcohol on muscle metabolism by using the isolated perfused hindlimb preparation.

Results: The phosphorylation of S6K1 and S6 in muscle was increased after injection of IGF‐I in control rats. In contrast, IGF‐I failed to stimulate S6K1 or S6 phosphorylation 2.5 hr after intraperitoneal administration of alcohol when the blood alcohol concentration was increased between ∼165 and 300 mg/dl. With a maximal suppressive dose of alcohol, the inhibitory effect on S6K1/S6 phosphorylation was observed as early as 1 hr and for up to 8 hr. The ability of alcohol to impair phosphorylation of S6K1 and S6 was independent of gender (male versus female), nutritional status (fed versus fasted), and route of alcohol administration (intraperitoneal versus oral). Furthermore, the suppressive effect of alcohol was still observed in rats pretreated with 4‐methylpyrazole, suggesting that the response was independent of the oxidative metabolism of ethanol. The direct effect of alcohol on IGF‐stimulated S6K1/S6 phosphorylation was also present when the isolated hindlimb was perfused in situ with buffer containing alcohol. In contrast to S6K1, acute alcohol intoxication did not consistently impair the ability of IGF‐I to stimulate 4E‐BP1 phosphorylation under any of the experimental conditions.

Conclusions: These data indicate that acute alcohol intoxication selectively impairs IGF‐I signaling via S6K1, but not 4E‐BP1, and that this defect is independent of gender, nutritional state, route of administration, and alcohol metabolism. The IGF‐I resistance may represent a participating mechanism by which alcohol directly limits the translation of selected messenger RNAs and, ultimately, protein synthesis in skeletal muscle.
Ethanol Induces Expression of the Glutamate Transporters EAAT1 and EAAT2 in Organotypic Cortical Slice Cultures
Authors: Zink Mathias , Schmitt Andrea , Vengeliene Valentina , Henn Fritz A. , Spanagel Rainer
Published: November 2004

Background: Exposure of the developing brain to ethanol disposes the fetus to fetal alcohol syndrome and causes a number of changes in several neurochemical systems. In particular, the glutamatergic system is affected by ethanol. Thus, increased sensitivity of glutamate receptors and enhanced transmembrane transport of glutamate were found in primary astrocyte cultures. However, in these in vitro studies, changes in the expression of glutamate transporters were not detected. To further characterize the influence of chronic ethanol exposure on the developing brain, we assessed the transcriptional and translational regulation of glutamate transporters in a less artificial in vitro system.

Methods: We exposed postnatal rat cortical organotypic slice cultures to ethanol (100 mM) for 4 and 8 days. Expression of the excitatory amino acid transporters EAAT1 and EAAT2 was analyzed in comparison to untreated controls with semiquantitative reverse transcriptase‐polymerase chain reaction. In addition, changes in protein expression were detected by Western blotting.

Results: In ethanol‐exposed cortical slices, we observed more prominent fiber outgrowth and significantly increased gene expression (EAAT1: +35%, p= 0.029; EAAT2: +251%, p= 0.015). These findings could be verified on the protein level, because Western blot analysis revealed significantly higher levels of EAAT1 (+76%; p= 0.008) and EAAT2 (+104%; p= 0.018) in ethanol‐treated slices compared with controls.

Conclusions: Our results are in concert with earlier studies describing the induction of glutamate transport by ethanol. Enhanced expression of EAAT1 and EAAT2 after ethanol exposure can be viewed as a maladaptive process that disposes the developing brain to fetal alcohol syndrome.
Wiener chaos and the Cox–Ingersoll–Ross model
Authors: Grasselli M. R. , Hurd T. R.
Published: November 2004

In this paper we recast the Cox–Ingersoll–Ross (CIR) model of interest rates into the chaotic representation recently introduced by Hughston and Rafailidis. Beginning with the ‘squared Gaussian representation’ of the CIR model, we find a simple expression for the fundamental random variable
X
∞
. By use of techniques from the theory of infinite–dimensional Gaussian integration, we derive an explicit formula for the
n
th term of the Wiener chaos expansion of the CIR model, for
n
= 0,1,2,…. We then derive a new expression for the price of a zero coupon bond which reveals a connection between Gaussian measures and Ricatti differential equations.
The hypoxia-induced paralogs Scylla and Charybdis inhibit growth by down-regulating S6K activity upstream of TSC in Drosophila
Authors: Reiling Jan H. , Hafen Ernst
Published: November 2004

Diverse extrinsic and intrinsic cues must be integrated within a developing organism to ensure appropriate growth at the cellular and organismal level. In Drosophila, the insulin receptor/TOR/S6K signaling network plays a fundamental role in the control of metabolism and cell growth. Here we show that scylla and charybdis, two homologous genes identified as growth suppressors in an EP (enhancer/promoter) overexpression screen, act as negative regulators of growth. The simultaneous loss of both genes generates flies that are more susceptible to reduced oxygen concentrations (hypoxia) and that show mild overgrowth phenotypes. Conversely, scylla or charybdis overactivation reduces growth. Growth inhibition is associated with a reduction in S6K but not PKB/Akt activity. Together, genetic and biochemical analysis places Scylla/Charybdis downstream of PKB and upstream of TSC. Furthermore, we show that scylla and charybdis are induced under hypoxic conditions and that scylla is a target of Drosophila HIF-1 (hypoxia-inducible factor-1) like its mammalian counterpart RTP801/REDD1, thus establishing a potential cross-talk between growth and oxygen sensing.
The typical products within food “glocalisation”
Authors: Mattiacci Alberto , Vignali Claudio
Published: November 2004

The choice of typical products as an area of autonomous business with great potential comes from the development of a scenario of supply made up of important trends – within wealthy countries – that simultaneously invested in: the economy, the agricultural sector, the agro‐food sector and, on the same level, in the tourist industry and (of consumption) in the cultural sector, in the broad sense. It is well‐known that the more significant traits of the matter are connected to the following elements: globalisation; the increased use of technology in agricultural production; the renewed concept of territory; the “philosophical” change of agricultural policies; the great fragmentation of the tourist industry; the tensions generated by public opinion towards subjects like food safety, exacerbated by recent shocking events (mad cow disease, GMO, etc.); and new food consumption behaviour. The definition and background of typical food products are located in these varied elements.
Brunello di Montalcino: how a typical wine could revive a poor country‐village
Authors: Mattiacci Alberto , Zampi Vincenzo
Published: November 2004

None of the numerous food products that comprise the Italian food tradition can boast of business revitalisation as much as that which involved the wine industry in Italy and in the rest of the world in the last decade. This is not the appropriate moment to consider the reasons for this change, nor is it the right place to compare the industrial situations of that time with those present today. Rapidly covering the field of the extensive history of the wine business, it is sufficient to cite certain simplified facts in order to show how the end user of the product – the consumer – has dramatically changed his consumption history, which initiated the process of regeneration of the business, a process never before seen, in the world of agricultural industries. The companies in the vine‐growing and wine‐making business have been both the driving force and the beneficiaries of this state of affairs. Indeed, to have a clearer picture, a hypothetical external person, observing the wine business panorama today, would notice clear features and company models, that are unrelated to the historical past of the industry.
Participation in decision making: a matter of context?
Authors: Scott‐Ladd Brenda , Marshall Verena
Published: November 2004

This paper reports findings on employee participation in decision making from a cross‐section of employees in the public, private and local government sectors in Western Australia. A contextual model of participation relevant to the prevailing industrial climate was developed, then tested using a structural equations modelling approach. Results suggest that participative decision making (PDM) directly contributed to task variety and autonomy, and through autonomy, task identity. Employees perceived that PDM contributed to performance effectiveness and led to greater gains in the workplace. An unexpected result was that these benefits did not contribute to increased job satisfaction or commitment despite PDM having a direct positive influence on job satisfaction, which in turn increases commitment. These findings support arguments that employees believe participation in decision making offers them substantial benefits, but suggests they are more ambivalent about increasing task demands and the gains they receive for this extra effort.
Finite element analyses and simulations of sheet metal forming processes
Authors: Mackerle Jaroslav
Published: November 2004

Sheet metal forming is a process of shaping thin sheets of metal by applying pressure through male or female dies or both. In most of used sheet‐formating processes the metal is subjected to primarily tensile or compressive stresses or both. During the last three decades considerable advances have been made in the applications of numerical techniques, especially the finite element methods, to analyze physical phenomena in the field of structural, solid and fluid mechanics as well as to simulate various processes in engineering. These methods are useful because one can use them to find out facts or study the processes in a way that no other tool can accomplish. Finite element methods applied to sheet metal forming are the subjects of this paper. The reason for writing this bibliography is to save time for readers looking for information dealing with sheet metal forming, not having an access to large databases or willingness to spend own time with uncertain information retrieval. This paper is organized into two parts. In the first one, each topic is handled and current trends in the application of finite element techniques are briefly mentioned. The second part, an Appendix, lists papers published in the open literature. More than 900 references to papers, conference proceedings and theses/dissertations dealing with subjects that were published in 1995‐2003 are listed.
Export performance as an antecedent of export commitment and marketing strategy adaptation
Authors: Filipe Lages Luis , Montgomery David B.
Published: November 2004

This paper argues that performance should be investigated as an independent variable. Using survey data of over 400 managers responsible for the main export ventures of Portuguese SMEs (small and medium exporters), this paper shows that past performance plays a crucial role in building SMEs' commitment to exporting and to the determination of their current marketing strategy. Findings also show that marketing strategy adaptation to the foreign market is particularly noted in firms exporting to the most developed markets, rather than in firms exporting to the most competitive environments. Future international marketing research is encouraged to focus on understanding both the direct and indirect relationships among past performance, firm's commitment to exporting, and current marketing strategy under the influence of external forces. Such a focus has the potential to enrich the theory and generate relevant managerial and public policy implications.
Characterisation of a new tripyrazole derivative as inhibitor for the steel corrosion in acid solution
Authors: Elayyachy M. , El Kodadi M. , Hammouti B. , Ramdani A. , Elidrissi A.
Published: November 2004

The inhibition of corrosion of steel in 1 M HCl solution by newly synthesised pyrazole derivatives has been studied by weight loss and polarisation techniques at 308°K. Its inhibitory power is compared to N,N′‐bis(3,5‐dimethylpyrazol‐1‐yl‐methyl)‐pentanolamine (Bipyr). The results obtained reveal that tripyrazole exhibits a good protection. Inhibition is found to increase with increase in inhibitor concentration. The inhibition behaviour of the compound has been explained on the basis of molecule size and charge density of adsorption active centres. The adsorption phenomenon obeys the Langmuir adsorption isotherm model.
Workspace technology's impact on individual privacy and team interaction
Authors: Peterson Tim O. , Beard Jon W.
Published: November 2004

One way organizations increase their competitive advantage is through innovative strategies that improve human performance. Human performance can be enhanced or constrained by situational factors that are introduced into the organization's work environment. One situational factor is the organization's workspace. This study examines the impact of a new workspace technology on individual privacy and on team interaction. The research found that the participants were generally satisfied with the visual privacy but not with the auditory privacy. The research also found that the participants were satisfied with the workspace's ability to facilitate team interaction. Implications of the findings are discussed.
Engaging marketing in performance measurement
Authors: Woodburn Diana
Published: November 2004

Marketing has habitually avoided performance measurement, pleading difficulties with quantification of its activities and their outcomes. As a result, in many companies marketing has become marginalized to a straightforward marketing communications, whereas, it should hold a pivotal role in the identification of customer needs, specification of the value sought and demand generation, interpreted in its widest sense. This paper shows how marketing and the rest of the organization should relate to each other in the process of customer and value development and delivery, on which business performance depends. It discusses the importance of marketing in four constituents of performance measurement; resources, processes, products/services and financial performance. The CIMBA model of marketing processes is used to demonstrate that there can be no return on marketing investment without delivery through core operations. The paper concludes that marketing and business performance measurement are indispensable to each other.
Measuring and benchmarking intellectual capital
Authors: Marr Bernard
Published: November 2004

The importance of intellectual capital (IC), as a prime value driver in today's knowledge‐based economy, is undisputed. Benchmarking is seen as a tool for identifying, understanding, and adopting best practices in order to increase operational performance. The paper explores techniques of benchmarking the operational management of IC. The research is based on a longitudinal action and case research in an R&D organization. The failure to benchmark IC management practices between two seemingly identical subsidiaries has implications for the measurement and benchmarking of IC. The research concludes that it is critical to understand the context, organizational epistemology and value‐creation pathways before organizations start any attempt to compare or benchmark IC.
Births and perinatal health of infants among women who have had silicone breast implantation in Finland, 1967–2000
Authors: Hemminki Elina , Hovi Sirpa‐Liisa , Sevón Tiina , Asko‐Seljavaara Sirpa
Published: November 2004

Background.  Potential problems with breast implants have been widely discussed, but few data exist on the childbearing and offspring of women with implants. The purpose of this study was to investigate the occurrence and conditions of pregnancies of women who have had cosmetic breast implantation (exposed women), and the health of their newborns.

Methods.  Women who had breast implants for cosmetic reasons in the period 1967–1999 (n = 2236) were identified from hospital surgical records. The births of the exposed women were identified through record linkage to the Population Register. The perinatal health of the infants was studied by the data in the Medical Birth Register in 1987–1999. For each birth to an exposed woman, 20 control mothers who gave birth in the same year were chosen randomly from the Medical Birth Register. Differences in mothers' background characteristics were adjusted by logistic regression.

Results.  The women had received their first cosmetic breast implants at young ages (mean 31 years). By year 2000, 26% of the exposed women had one or more children. Half of these women had not had a liveborn child before getting implants. Of the 1661 exposed women who had not (yet) had children, 32% were less than 35 years of age at the end of follow‐up. The women had children at a mean of 4.7 years after the implants. Some of the perinatal health indicators suggested poorer health and others better health for infants of exposed women, but only transfers to other hospitals and lower birthweight among infants of exposed multipara were statistically significant.

Conclusions.  The study shows that pregnancy and infant health are relevant considerations with regard to breast implants; further studies on implants are needed.
Subclinical abnormalities of glucose metabolism in Brazilian women with a history of gestational diabetes mellitus
Authors: Pimenta Walkyria P. , Calderon Iracema M. P. , Cruz Ney S. , Santos Maria Luiza , Aragon Flávio F. , Padovani Carlos Roberto
Published: November 2004

Background.  To evaluate insulin release and insulin sensitivity in women with prior gestational diabetes mellitus (GDM) to gain a better understanding of type 2 diabetes pathogenesis.

Methods.  GDM women were individually matched for age, body mass index, and waist/hip ratio with those who were normal glucose tolerant in a previous pregnancy (NGT). All women presented with normal glucose tolerance. Twenty pairs were submitted to the oral glucose tolerance test (OGTT) with plasma glucose, insulin, and C‐peptide determinations. Of the 20 pairs, 18 participated in hyperglycemic (10.0 mmol/l) clamp experiments with frequent plasma glucose and insulin determinations, allowing us to calculate first‐ and second‐phase insulin release and the insulin sensitivity index. GDM and NGT women were compared using Student's t‐test, the Mann–Whitney U‐test, Friedman's non‐parametric test, and the two proportion test for independent groups.

Results.  GDM women showed higher glycosylated hemoglobin values; at OGTT, they showed late insulin peak with increased plasma insulin levels only during the second hour, and a similar plasma C‐peptide response despite a higher plasma glucose curve; during hyperglycemic clamp procedures, they showed similar biphasic insulin release and insulin sensitivity index. Considering that a woman with previous GDM had a defect in insulin release and/or insulin sensitivity, if its magnitude was at least 25% lower than that of the matched NGT woman, 43.8% showed impairment of first‐phase insulin release and 55.6% insulin resistance.

Conclusions.  GDM women showed some degree of glucose intolerance. It is therefore necessary to follow them for a longer time.
Reproductive factors and extreme levels of maternal serum alpha‐fetoprotein: a population‐based study
Authors: Lei Ulrikke , Wohlfahrt Jan , Christens Peter , Westergaard Tine , Lambe Mats , Nørgaard‐Pedersen Bent , Melbye Mads
Published: November 2004

Background.  Levels of maternal alpha‐fetoprotein (AFP) are increased during multiple gestations and preeclampsia but little is known regarding AFP levels in relation to other reproductive factors. Consequently, the objective of this work was to describe the possible relationship between AFP levels during pregnancy and maternal age at birth, maternal age at first birth, parity, time since previous birth and gender of the offspring.

Methods.  Based on national registries we obtained the reproductive history on a population‐based cohort of 44 227 women who had serum AFP levels determined in gestational weeks 14–21 and whose present and previous pregnancies resulted in live‐born singletons.

Results.  Many previous births and an interval of less than 2 years since last birth were significantly associated with extremely low levels of AFP in the mother. However, age at first birth and age at present pregnancy did not influence the AFP level. Women who gave birth to a girl had AFP levels that were 5%[95% confidence interval (CI) 4–6%] lower than those of women who had a boy. Adjustment for birthweight did not significantly affect the estimate.

Conclusions.  Low serum AFP levels in pregnancy are significantly correlated with high parity and with a short interval between births. The significantly lower levels of AFP in women who gave birth to girls could indicate a possible gender‐specific regulatory mechanism.
Infertility and celiac disease: do we need more than one serological marker?
Authors: Shamaly Hussein , Mahameed Ahmad , Sharony Asher , Shamir Raanan
Published: November 2004

Objectives.  Celiac disease (CD) prevalence is higher in women with infertility. Our study aims were to evaluate the prevalence of undiagnosed CD in Arab infertile women and to explore the usefulness of using more than one serological marker in the diagnostic screening for CD in this population.

Methods.  Women with unexplained infertility (n = 192) and age‐matched healthy controls (n = 210) were prospectively enrolled. Serum was tested for human tissue transglutaminase antibodies (TTG), antiendomysial antibodies (EMA), and immunoglobulin A. Intestinal biopsy was offered to women with positive serology or immunoglobulin A (IgA) deficiency.

Results.  CD was diagnosed in five infertile women (2.65%) and in one control (0.5%) (p = 0.11). Gastrointestinal complaints were present in 60% (three of five) of women with CD and 11.8% (22 of 187) of women without CD (p = 0.017). Anemia was reported in 80% of infertile women with CD and 4.8% of infertile women without CD (p = 0.0001).

Conclusions.  Undiagnosed CD is prevalent in Arab infertile women as well as in Arab women in general. CD in Arab infertile women is frequently associated with gastrointestinal complaints and anemia. EMA testing is sufficient in suspected cases.
SOMATIC CELL FLAGELLAR APPARATUSES IN TWO SPECIES OF VOLVOX (CHLOROPHYCEAE)1
Authors: Hoops Harold J.
Published: November 2004

The somatic cell flagellar apparatuses of Volvox carteri f. weismannia (Powers) Iyengar and V. rousseletii G. S. West have parallel or nearly parallel basal bodies which are separated at their proximal ends. The four microtubular rootlets alternate between two and four members, and all are associated with a striated microtubular associated component (SMAC) that runs between the basal bodies. In addition, each half of the flagellar apparatus apparently rotates during development and loses the 180° rotational symmetry characteristic of most unicellular chlorophycean motile cells. All of these features appear necessary for efficient motion of a colony composed of numerous radially arranged cells. However, the structural details of the flagellar apparatuses of these two species differ. The distance between flagella is greater in V. rousseletii than in V. carteri. One distal striated fiber and two proximal striated fibers connect the basal bodies in V. carteri, but both types of fibers are absent from V. rousseletii. In the latter species, a striated fiber wraps around each of the basal bodies and attaches to the rootlets and the SMAC. No such fiber is present in V. carteri. Since the similarities in the flagellar apparatuses can be explained as a result of adaptation for efficient colonial motion in organisms with similar colonial morphology, the differences suggest a wider phylogenetic distance than previously believed.
PHOSPHORUS STATUS AND CYTOPLASMIC STRUCTURES IN SCENEDESMUS (CHLOROPHYCEAE) UNDER DIFFERENT METABOLIC REGIMES1
Authors: Tillberg Jan‐Eric , Barnard Tudor , Rowley John R.
Published: November 2004

Phosphorus deficiency affects the anatomy of the unicellular green alga Scenedesmus obtusiusculus Chad. and influences the distribution of other inorganic elements in the cell in addition to phosphorus. Scenedesmus was grown under standard conditions with or without phosphorus. Cells were then cultured with phosphorus under conditions favouring glycolysis, respiration, or photophosphorylation for 2 h or photosynthesis for up to 8 h. The dominating features of phosphorus starvation, were loss of phosphorus and coions from polyphosphate bodies, accumulation of starch, decrease in the volume density of ribosomes both in the chloroplast and cytoplasm, and an increase in wall thickness. Under conditions favoring photosynthesis the mass fraction for phosphorus is low after 1 h, exceptionally high by 2 h, and diminishes by 8 h. High amounts of phosphorus are also regained under conditions favoring glycolysis and photophosphorylation but not respiration. After 2 h under photosynthetic conditions the volume densities of the chloroplast, cytoplasmic ribosomes, the vacuole, and the mitochondrion increased over controls. By 8 h the relative volume of the single ramified mitochondrion had decreased slightly and recognizable segments of it were sequestered within the vacuome. The autophagic nature of the vacuole was further evidenced by the presence of ribosomes and whorls of lamellae within it. Serial sections showed that all polyphosphate granules and sequestered materials were located within a continuous vacuolar cisterna.
MICRONUTRIENT UPTAKE AND TRANSLOCATION BY MACROCYSTIS PYRIFERA (PHAEOPHYTA)1
Authors: Manley Steven L.
Published: November 2004

Radionuclides of the micronutrients (Mn, Co, Cu, Zn, Mo, and I) of Macrocystis pyrifera (L.) C. Ag. and the nonnutrient Ni were concentrated in sieve tube sap. Micronutrient uptake rates of mature blade tissue were determined using the appropriate radionuclide in artificial seawater. Cellular uptake was distinguished from free space uptake by the use of suitable wash solutions. The uptake rates were then transposed to conditions in the sea, with several assumptions being made. Micronutrient content was determined for mature blade tissue before and after treatment to remove extracellular micronutrients. A mathematical description of frond growth was developed from previously published data and used to derive equations relating micronutrient assimilation (tissue incorporation) and uptake by fronds, both expressed in mg·d−1, to frond length. Calculations revealed that at a certain frond length xi assimilation equaled uptake for Mn, Co, and Fe. Uptake was greater than assimilation for fronds longer than xi and less than assimilation for fronds shorter than xi. This indicated that Mn, Co, and Fe translocation was required from fronds longer than xi to fronds shorter than xi. The large assimilation values at xi for Mn and Co further indicate that these elements, at times, may limit Macrocystis growth. Calculations also showed that Cu, Zn, Mo, I, and Ni uptake was greater than their assimilation for all frond lengths, which suggested that these elements are transported to other tissues for storage (e.g. in holdfast) or release (e.g. from frond apices).
GYMNODINIUM ACIDOTUM NYGAARD (PYRROPHYTA), A DINOFLAGELLATE WITH AN ENDOSYMBIOTIC CRYPTOMONAD1
Authors: Wilcox Lee W. , Wedemayer Gary J.
Published: November 2004

Ultrastructural examination of the freshwater, blue‐green dinoflagellate Gymnodinium acidotum Nygaard revealed the presence of an endosymbiotic cryptomonad. Features of the endosymbiont allying it with the Cryptophyceae include mitochondria with flattened cristae, paired thylakoids with electron‐dense contents, and nucleomorphs, bodies unique to the Cryptophyceae. This report is the first conclusive documentation of a symbiosis involving these two groups.
RESPONSES OF CERTAIN FRESHWATER PLANKTONIC ALGAE TO FLUORIDE1
Authors: Hekman Wilhelmina E. , Budd Kenneth , Palmer Gerald R. , MacArthur J. Duncan
Published: November 2004

The effects of dissolved fluoride supplied as NaF at up to 150 p.p.m. F− (7.9 mM) on growth, photosynthesis, dark respiration, enolase activity and fluoride uptake were determined for six phytoplankters: Synechococcus leopoliensis (Racib.) Komarek (Cyanophyta), Oscillatoria limnetica Lemmermann (Cyanophyta), Ankistrodesmus braunii Brun (Chlorophyta), Scenedesmus quadricauda (Turp.) Bréb. (Chlorophyta), Cyclotella meneghiniana Kützing (Bacillariophyta) and Stephanodiscus minutus Grun. ex Cleve et Moll (Bacillariophyta). Growth (determined by absorbance at 660 nm or by cell‐numbers) was unaffected by fluoride at up to 50 p.p.m. (2.6 mM) in all algae except S. leopoliensis, in which growth ceased transiently followed by resumption of growth at reduced rate. These effects showed a threshold at ca. 25 p.p.m. (1.3 mM) F− and increased with increasing F− concentration above this threshold. Photosynthetic O2 evolution in the chlorophytes was unaffected by F− at up to 50 p.p.m., whereas in S. leopoliensis F− above ca. 25 p.p.m. caused a concentration‐dependent inhibition of photosynthesis which was most pronounced at saturating irradiance. Dark O2 uptake was unaffected at up to 50 p.p.m. in chlorophytes but was stimulated in S. leopoliensis. Enolase in clarified cell‐extracts of all six algae was inhibited by F−, with Ki values ranging from 27 to 319 μM. Fluorine (measured by proton‐induced gamma‐ray emission) could not be detected in chlorophytes exposed during growth to up to 50 p.p. m. F−, but was detected in S. leopoliensis, O. limnetica and C. meneghiniana. Fluorine associated with cells of these algae increased as the external F− concentration increased.
CARBOXYSOME CONTENT OF SYNECHOCOCCUS LEOPOLIENSIS (CYANOPHYTA) IN RESPONSE TO INORGANIC CARBON1
Authors: Turpin David H. , Miller A. G. , Canvin David T.
Published: November 2004

The carboxysome content of chemostat grown Synechococcus leopoliensis (Racib.) Komarek increases under inorganic carbon limitation. At growth rates of ca. 85%μmax the carboxysome content (±SE) was 0.57 ± 0.09 carboxysomes·cell section−1. Under severe carbon limitation (ca. 13%μmax) this increased to 3.4 · 0.3 carboxysomes·cell section−1. Corresponding to this change is a three order of magnitude decrease in the half‐saturation constant of photosynthesis for dissolved inorganic carbon. Nitrogen and phosphorus limitation had no effect on carboxysome content or the kinetics of photosynthesis with respect to inorganic carbon. These results are discussed in light of the apparent lack of photorespiration in these organisms.
MORPHOLOGICAL VARIABILITY OF EUNOTIA PECTINALIS (BACILLARIOPHYCEAE) IN A SOFTWATER RHODE ISLAND STREAM AND IN CULTURE1
Authors: Steinman Alan D. , Sheath Robert G.
Published: November 2004

The diatom Eunotia pectinalis (O. F. Müll.?) Rabh. exhibited considerable morphological variability in samples collected over a 13‐month period from a softwater Rhode Island stream. All observed morphotypes were classified into three main complexes based upon their valve configuration. These groupings were confirmed by discriminant analysis using quantitative valve characteristics and were named in accordance with their associated varieties: minor (Kütz.) Rabh., pectinalis and ventricosa Grun. Clonal cultures were subjected to a defined series of temperatures, agitation rates and light intensities in order to assess inherent morphological variability. Similar trends were evident for all complexes. Over time, valve length decreased, valve breadth enlarged, and striae number per 10 μm at valve center and apex increased. Morphological plasticity was evident in culture and appeared to be more a function of the clone genotype than the environmental conditions to which it was subjected. One clone originally identified as E. pectinalis var. minor assumed certain morphological features of E. vanheurckii Patr. after four months in culture.
AN ELECTRON MICROSCOPE STUDY OF GAMETE RELEASE AND SETTLING IN THE COMPLANATE FORM OF SCYTOSIPHON (SCYTOSIPHONACEAE, PHAEOPHYTA)1
Authors: Clayton Margaret N.
Published: November 2004

This paper describes the ultrastructural characteristics of gametes and their liberation from the gametangia in Scytosiphon sp., a brown alga showing only slight sexual differentiation. Both male and female gametes are released initially into a central cavity which forms in the gametangial sorus by the extensive dissolution of the internal cell walls. Scytosiphon sp. gametes possess structural features in common with the zoids of other species of brown algae. Gamete fine structure is discussed in relation to cell function. After release from the gametangial sorus, female gametes can be distinguished from males by the presence of a large number of Golgi‐derived vesicles with electron dense cores. It is possible that these vesicles contain the sex attractant compound. When gametes settle they become spherical, the flagella and eyespot are withdrawn into the cell and adhesive material, apparently originating from the activity of the Golgi body, appears on the surface of the cell.
GROWTH RESPONSE OF A NITROGEN FIXER (ANABAENA FLOS‐AQUAE, CYANOPHYCEAE) TO LOW NITRATE1
Authors: Elder Robert G. , Parker Michael
Published: November 2004

Anabaena flos‐aquae (Lyngb.) Bréb. was grown in varying concentrations of nitrate. Specific growth rates, as estimated in batch culture, were constant and approached the maximum rate at all concentrations of NO3−‐N tested bewteen 0 and 400 μ/L. Steady‐state biomass, as determined in semicontinuous culture, did not vary with NO3− at slower dilution rates. However at a faster dilution rate, significantly less biomass occurred in intermediate concentrations of NO3− than in either higher or lower concentrations. The results indicate that both growth rate and standing crop are maximized by either N2 fixation or NO3− assimilation, but extracellular NO3− reduces the rate of N2 fixation. Consequently, at very low NO3− concentrations, growth is virtually maximized by N2 fixation alone, and at high concentrations of NO3−, N2 fixation is inhibited but growth is maximized by assimilation of NO3−. At intermediate concentrations of NO3−, growth becomes a function of NO3− assimilation augmented by N2 fixation. In this case, full growth potential is realized only if hydraulic residence time is sufficiently long to compensate for the reduced rate of N2 fixation. Growth rate and standing crop are not diminished in response to the large amount of energy allocated to N2 fixation. Instead, other cellular processes are probably affected negatively during N2 fixation.
CYTOLOGY AND ULTRASTRUCTURE OF CHLORARACHNION REPTANS (CHLORARACHNIOPHYTA DIVISIO NOVA, CHLORARACHNIOPHYCEAE CLASSIS NOVA)1
Authors: Hibberd David J. , Norris Richard E.
Published: November 2004

The green amoeboid cells of Chlorarachnion reptans Geitler are completely naked and each contains a central nucleus, several bilobed chloroplasts each with a central projecting pyrenoid enveloped by a capping vesicle, several Golgi bodies, mitochondria with tubular cristae, extensive rough ER, and a distinct layer of peripheral vesicles. Complex extrusome‐like organelles occur rarely in both the amoeboid and flagellate stages. The only organelles entering the reticulopodia are mitochondria, but microtubules are also present. The chloroplasts contain chlorophylls a and b, but histochemical tests suggest that the carbohydrate storage product probably is not a starch. The chloroplast lamellae are composed of one to three thylakoids or form deep stacks. A girdle lamella and interlamellar partitions are absent. Each chloroplast is bounded by either four separate membranes, a pair of membranes with vesicular profiles between them, or three membranes; all three arrangements may occur in the same chloroplast. A periplastidal compartment occurs near the base of the pyrenoid where there are always four surrounding membranes. The compartment has a relatively dense matrix and contains ribosome‐like particles and small dense spheres; it extends over and into a deep invagination in the pyrenoid where its contents are enclosed in a double‐membraned envelope which is penetrated by wide pores. The zoospores are ovoid and each bears a single laterally inserted flagellum which appears to be wrapped helically around the cell body during swimming. The flagellum lies in a groove in the cell surface and bears fine lateral hairs. Neither a second flagellum or vestige of one, nor an eyespot, is present. A single microtubular root and a larger homogeneous root run from the flagellar base parallel to the emerging flagellum, between the nuclear envelope and the plasmalemma. In the simple flagellar transition region, fine filaments connect adjacent axonemal doublets. A detailed comparison of C. reptans with all other algal taxa results in the conclusion that it must be segregated in the new class Chlorarachniophyceae, the only class in the new division Chlorarachniophyta. The possibility that C. reptans evolved from a symbiosis between a colorless amoeboid cell and a chlorophyll b‐ containing eukaryote is considered, but the possible affinities of the symbiont remain enigmatic. The implications of the unique chloroplast structure of C. reptans for current hypotheses concerning the origin of chloroplasts are discussed.
OBSERVATIONS ON THE LIFE HISTORY OF PAPENFUSSIELLA CALLITRICHA (PHAEOPHYCEAE, CHORDARIALES) IN CULTURE1
Authors: Peters Akira F.
Published: November 2004

Papenfussiella callitricha (Rosenv.) Kylin from eastern Canada was studied in culture. Zoids from unilocular sporangia develop into microscopic, filamentous, dioecious gametophytes which produce isogametes in filament cells and few‐chambered plurilocular gametangia. Unfused gametes germinate to reproduce the gametophytes. Fusion takes place between a settled (“female”) and a motile (“male”) gamete. The zygote gives rise to a filamentous plethysmothallus that reproduces asexually by zoids formed in thallus cells and in few‐chambered plurilocular zoidangia. Erect macrothalli are produced on the plethysmothallus, beginning with the formation of upright filaments. Later on, these filaments become the terminal assimilators of the macrothalli. Further assimilatory filaments, rhizoids, and unilocular sporangia are produced in a branching region at the base of the terminal assimilator. Zoids from unilocular sporangia formed in culture germinate to reestablish the gametophyte phase. Chromosome counts yielded n = 19 ± 3 for the gametophytes, and 32 ± 6 for the sporophyte, both plethysmothallus and macrothallus.
LYSIS OFMICROCYSTIS AERUGINOSA(KÜTZ.) BYBDELLOVIBRIO‐LIKE BACTERIA1
Authors: Caiola Maria Grilli , Pellegrini Stefania
Published: November 2004

Cells ofMicrocystis aeruginosa(Kützing), collected from water‐blooms of Lake Varese, were lysed byBdellovibrio‐like bacteria. The cells were lysed only after penetration. The cyanobacteria and lysing bacteria were characterized by a fibrous glycocalyx. Once the host cell was penetrated, the bacteria remained localized mainly between the host cell wall and cytoplasmic membrane, which appeared partially thickened. Cell lysis began by breakdown of cell structures. The cell wall appeared broken at many sites, and in completely lysed cells, was partially interrupted. The lysis ofMicrocystisby bacteria could be one of the causes of the death of algal blooms.
PERIPHYTON COLONIZATION OF ROCK SURFACES IN A BOREAL FOREST STREAM STUDIED BY SCANNING ELECTRON MICROSCOPY AND TRACK AUTORADIOGRAPHY1
Authors: Hamilton Paul B. , Duthie Hamish C.
Published: November 2004

Periphyton colonization of natural rock surfaces and granite tiles was followed experimentally in the Matamek River, an acidic (pH 5.5) sixth order boreal stream in northeast Quebec, Canada. Accumulation of chlorophyll a and freshweight algal biomass was logarithmic over a 25 day colonization period. The major colonizers were Tabellaria flocculosa (Roth) Kütz., T. fenestrata (Lyngb.) Kütz., Mougeotia sp., and Eunotia pectinalis (Kütz) Rabh., and its varieties. The microcolonization sequence on granite tiles, followed over 27 days with scanning electron microscopy, showed an initial accumulation of algal cells on the upstream and downstream margins and in depressions, followed by a gradual filling‐in of the flat surfaces. It is hypothesized that the observed slow rate of colonization was due to the high surface tension of the granite substratum and the absence of preconditioning by an organic film. It is further hypothesized that the increase in cellular carbon fixation rates of T. flocculosa measured over a 23 day period using nuclear track autoradiography parallels the development of an algal‐detrital microcosm on the granite tile, and is evidence for the establishment of localized tight nutrient spiralling. It is suggested that the periphyton community may be regarded as a nutrient recycling system at a microenvironmental level which may be especially important in oligotrophic systems.
TAXONOMIC REVISION OF THE CONJUGATOPHYCEAN FAMILY PENIACEAE ON THE BASIS OF CELL WALL ULTRASTRUCTURE1
Authors: C.Kouwets Frans A. , M.Coesel Peter F.
Published: November 2004

An ultrastructural investigation of the cell wall of Penium silvae‐nigrae Raban. and P. spinospermum Josh. showed that these species possess true pores with a pore apparatus and overlapping semi‐cell walls. It follows that these two taxa belong not to the Peniaceae, but to the Desmidiaceae sensu stricto; they are referred to the genus Actinotaenium Teil. on account of the shape of their cells and chloroplasts. Two other species previously included in Penium Bréb. are referred to Actinotaenium. Although their cell wall structure could not be studied, they are distinguished from “typical” representatives of Penium by the following photomicroscopically observable complex of features: (pseudo‐) girdle bands none, cell wall pores in longitudinal rows, zygospores not globose but of irregular shape. The following new combinations ensued: Actinotaenium borgeanum (Skuja), A. phymatosporum (Nordst.), A. silvae‐nigrae (Raban.), A. silvaenigrae var. parallelum (Krieger) and A. spinospermum (Josh.). In addition the diagnosis of the genus Penium was emended and P. margaritaceum (Ehr.) ex Bréb. was selected as the lectotype species. The family Gonatozy‐gaceae is merged into the Peniaceae on the basis of cell wall structure.