bluuebunny/crossref_metadata_2025 huggingface dataset:
Arachidonic acid release from NIH 3T3 cells by group‐I phospholipase A2: Involvement of a receptor‐mediated mechanism
Authors: Xing Mingzhao , Miele Lucio , Mukherjee Anil B.
Published: February 2005

Group I pancreatic phospholipase A2 (PLA2 I) is primarily a digestive enzyme. Recently, however, in addition to its catalytic activity a receptor‐mediated function has been described for this enzyme. PLA2 I binding to its receptor induces cellular chemokinesis, proliferation, and smooth muscle contraction. This enzyme also induces the production of prostaglandin E2 in certain cells and may have a proinflammatory role. However, despite its ability to hydrolyze phospholipids in in vitro assays, PLA2‐I does not efficiently catalyze release of AA from intact cells. Here, we demonstrate that while short‐term exposure of NIH 3T3 cells to PLA2‐I is ineffective, exposure of 6 h or longer significantly increases the basal release of AA. Dose‐response curve of PLA2‐I‐induced AA release was saturable with an EC50 of 14.01 ± 1.36 nM (n = 3). [3H]‐AA was preferentially released over [3H]‐oleic acid by PLA2‐I, inactivated with 4‐bromophenacyl bromide, was fully capable of mediating AA release. These data suggest that a non‐catalytic, receptor‐mediated mechanism is involved in PLA2‐I‐induced AA release in NIH‐3T3 cells. This relase of AA is not dependent on protein kinase C or Ca2+ concentration. Comparison of the effect of PLA2‐I with those of ATP and platelet‐derived growth factor indicates that each of these agonists regulates AA release via independent pathways. Neither the basal enzymatic activity of the 85‐kDa cytosolic PLA2 nor the protein level of this enzyme was affected by treatment of cells with PLA2‐I. However, the increase in basal enzymatic activity of 85 kDa PLA2 due to protein kinase C activation was further enhanced by pretreatment of cells with PLA2‐I. We conclude that: (1) short‐term exposure of cells to PLA2 I does not cause measurable AA release; (2) release of AA from intact cells by this enzyme requires long‐term exposure; (3) AA release is not mediated by a direct catalytic effect of PLA2 I; and (4) AA release by PLA2 I is accomplished via a receptor‐mediated process. Taken together, these results raise the possibility that PLA2 I, in addition to its digestive function, may also contribute to aggravate preexisting inflammatory processes and/or to initiate new ones when chronic exposure of cells to this enzyme occurs. © 1995 Wiley‐Liss Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Expression and regulation of superoxide dismutase activity in human skin fibroblasts from donors of different ages
Authors: Allen P. G. , Keogh Bart P. , Gerhard Glenn S. , Pignolo Robert , Horton Joseph , Cristofalo Vincent J.
Published: February 2005

We have determined the activities, protein, and mRNA abundances as well as the level of transcriptional activation of two intracellular forms of the free radical metabolizing enzyme superoxide dismutase in 29 human skin fibroblast lines established from donors of different ages. SOD‐1 (a copper and zinc containing from of SOD) and SOD‐2 (a manganese containing form of the enzyme) activities were both observed to be significantly lower in cell lines derived from fetal skin than in lines established form postnatal skin (ages 17–94 years). The percent of total activity contributed by SOD‐1 decreased in an age‐associated manner from approximately 50% in the fetal lines to less than 20% in lines established from old tissue donors. All of the cell lines were screened to exclude the possibility that they contained a polymorphism known to influence SOD‐2 activity. Northern blot analysis revealed three SOD‐1 mRNA transcripts that were 0.5, 0.7, and 1.9 kb in length. Although SOD‐1 protein abundance was lower in fetal lines than in lines derived from postnatal donors, SOD‐1 mRNA abundance did not differ between fetal cells and cell lines derived from young donors. SOD‐2 protein abundance and mRNA abundance were both significantly lower in fetal lines than in postnatal lines. No postnatal age‐dependent differences were observed in any of the SOD‐2 parameters examined. Nuclear run‐on analysis revealed that fetal cell lines exhibited a lower level of transcriptional initiation for SOD‐1 than postnatal lines. The transcription of SOD‐2 was readily detected in postnatal lines, but undetectable in fetal lines. These results are consisten with multiple levels of control of SOD‐1 expression and with a strong transcriptional influence on SOD‐2 expression. © 1995 Wiley‐Liss Inc.
Contribution of increased glutathione content to mechanisms of oxidative stress resistance in hydrogen peroxide resistant hamster fibroblasts
Authors: Spitz Douglas R. , Kinter Michael T. , Roberts Robert J.
Published: February 2005

An H2O2‐resistant variant (OC14) of the HA1 Chinese hamster fibroblast cell line, which demonstrates cross resistance to 95% O2 and a 2‐fold increase in total glutathione content, was utilized to investigate mechanisms responsible for cellular resistance to H2O2‐ and O2‐toxicity. OC14 and HA1 cells were pretreated with buthionine sulfoximine (BSO) to deplete total cellular glutathione. Following BSO pretreatment, cells were either placed in 250 μM BSO to maintain the glutathione depleted condition and challenged with 95% O2, or challenged with hydroged peroxide in the absence of BSO. Total glutathione and the activities of CuZn superoxide dismutase, Mn superoxide dismutase, catalase, glutathione peroxidase, and glutathione transferase were evaluated immediately following the BSO pretreatment as well as following 39 to 42 hr of exposure to 250 μM BSO. BSO treatment did not cause significant decreases in any cellular antioxidant tested, except total glutathione depletion resulted in significant (P < 0.05) sensitization to O2‐toxicity and H2O2‐toxicity in both cell lines at every time point tested. However, glutathione depletion did not completely abolish the resistance to either O2‐ or H2O2‐toxicity demonstrated by OC14 cells, relative to HA1 cells. Also, glutathione depletion did not effect the ability of OC14 cells to metabolize extracellular H2O2. These data indicate that glutathione dependent processes significantly contribute to cellular resistance to acute H2O2‐ and O2‐toxicity, but are not the only determinants of resistance in cell lines. The contribition of aldehydes formed by lipid peroxidation in mechanisms involved with the sensitization to O2‐toxicity in glutathione depleted cells was tested by measuring the lipid peroxidation byproduct, 4‐hydroxy‐2‐nonenal (4HNE), bound in Schiff‐base linkages or in its free form in cell homogenates at 49 hr of 95% O2‐exposure. No significant increase in 4HNE was detected in glutathione depleted cells relative to glutathione competent cells, indicating that glutathione depletion does not sensitize these cells to O2‐toxicity by altering the intracellular accumulation of free or Schiff‐base bound 4HNE. © 1995 Wiley‐Liss Inc.
L‐fucose reduces collagen and noncollagen protein production in cultured cerebral microvessel endothelial cells
Authors: Yorek Mark A. , Conner Corinne E. , Spanheimer Robert G.
Published: February 2005

L‐fucose is a monosaccharide which is present in low concentrations in normal serum but is increased in diabetes, cancer, and inflammatory diseases. The contribution that abnormal L‐fucose levels make to the progression of these disorders is unknown. In a previous study we showed that increased L‐fucose concentration reduced proliferation and proteoglycan production by cultured cerebral microvessel endothelial cells. In the present study we show that exposing cerebral microvessel endothelial cells for 2 weeks to medium containing an increased concentration of L‐fucose causes a significant decrease in collagen and to a lesser extent noncollagan protein production. The effect of L‐fucose on collagen and noncollagen protein production is concentration‐dependent: 1 mM L‐fucose causes a significant decrease in collagen production but has no effect on noncollagen protein production; a 5mM L‐fucose concentration causes a maximum decrease in both collagen and noncollagen protein production. This defect is unrelated to the reduction in myo‐inositol uptake caused by L‐fucose and is not prevented by aminoguanidine. Collagen production can be improved by restoring L‐fucose‐conditioned cells to normal medium. Culturing cells for 2 weeks in medium containing 10 mM L‐fucose resulted in a 50% decrease in collagen production, which was restored to 75% of control after cells were transferred to normal medium for 7 days. In contrast, noncollagen protein production was totally restored after 3 days in normal medium. Increasing levels of L‐fucose in serum of rats also resulted in a decrease in collagen production. Collagenase digestible incorporation of L‐[2,3,4,5‐3H]proline into protein of the articular cartilage from rats fed a diet containing 20% L‐fucose for 3 weeks was reduced by about 40% compared to rats fed a normal diet. The decrease in collagen production in L‐fucose fed rats was less than the reduction that occurred in streptozotocin‐induced diabetic rats. These data suggest that changes in L‐fucose concentration itself may be a factor in the regulation of collagen production. © 1995 Wiley‐Liss Inc.
Proto-oncogene homologous sequences in the sea urchin genome
Authors: Mifflin David , Robinson John J.
Published: February 2005

Using probes specific for several oncogenes/proto-oncogenes we have performed gel blot hybridization analyses of genomic DNA isolated from the sea urchin Strongylocentrotus droebachiensis. Probes prepared from v-erbB, v-myc, c-myb and v-fps were found to hybridize with discrete fragments of HindIII digested genomic DNA. In contrast, probes prepared from v-abl, v-fos, v-sis, v-src, and v-mos either hybridized with multiple fragments, indicating non-specific binding, or failed to hybridize at all above background levels. These results clearly demonstrate the presence of proto-oncogene homologous sequences in the sea urchin genome.
Structure of a gap junction gene: Rat connexin-32
Authors: Miller Todd , Dahl Gerhard , Werner Rudolf
Published: February 2005

A genomic clone for the rat liver gap junction protein (connexin-32) was isolated and characterized by restriction enzyme mapping and sequence analysis. While the complete coding sequence is contained within one uninterrupted block, the 5′-untranslated region of the transcript contains a 6.1 kb intron. Both S1 nuclease protection and primer extension assays indicate multiple transcription start sites. Sequences homologous to cAMP response elements are found near the transcription start sites and within the 3′-end of the intron.
Effect of noradrenaline chronic administration on brown fat phospholipids
Authors: Mory Gérard , Gawer Myriam , Kader Jean-Claude
Published: February 2005

Chronic cold exposure of rats (9 days at 5°C) induces an alteration of the fatty acid composition of phospholipids in brown adipose tissue. The alteration is due to an increase of the unsaturation degree of these lipids. The phenomenon can be reproduced by 10−7 mole. h−1 administration of noradrenaline for 9 days in rats kept at 25°C. Thus, phospholipid alteration in brown fat of cold exposed rats is most probably a consequence of the increase of sympathetic tone which occurs in this tissue during exposure to cold.
Release of neuropeptides does not only occur at nerve terminals
Authors: Nordmann Jean J. , Dayanithi Govindan
Published: February 2005

Neurohypophysial hormones are packed in secretory granules which are stored in nerve endings and in dilatations called nerve swellings. Although it was originally believed that the nerve swellings were storage compartments and that release occurred solely from the nerve terminals, the present paper demonstrates that secretion can occur to the same extent from both nerve endings and nerve swellings.
The relationship between ambient lighting conditions, absolute
dark-adapted thresholds, and rhodopsin in black and hypopigmented
mice
Authors: DALY GERARD H. , DILEONARDO JESSICA M. , BALKEMA NATALIE R. , BALKEMA GRANT W.
Published: February 2005

Significant variation in absolute dark-adapted thresholds is observed
both within and between strains of mice with differing ocular
pigmentation levels. Differences in threshold within a single strain
are related to the Williams' photostasis effect, that is,
photoreceptor rhodopsin levels are dependent upon ambient lighting
conditions. To examine threshold differences among strains, we
equalized rhodopsin levels by maintaining albino mice
(c2J/c2J) at 2 × 10−4
cd/m2 (dim light) and black mice at 2 ×
102 cd/m2 (bright light). This resulted in
ocular rhodopsin levels for albino mice (albino—dim) of 494
± 11 pmoles/eye and rhodopsin levels for black mice
(black—bright) of 506 ± 25 pmoles/eye. For comparison,
rhodopsin levels in black mice maintained in dim light are 586 ±
46 pmoles/eye and 217 ± 46 pmoles/eye in albino mice
maintained in bright light. We found similar dark-adapted thresholds
(6.38 log cd/m2vs. 6.47 log
cd/m2)) in albino and black mice with equivalent
rhodopsin determined with a water maze test. This suggests that
dark-adapted thresholds are directly related to rhodopsin levels
regardless of the level of ocular melanin. The number of
photoreceptors, photoreceptor layer thickness, and outer segment length
did not differ significantly between albino (dark) and black mice
(bright). These results demonstrate that the visual sensitivity defect
found in hypopigmented animals is secondary to abnormal rhodopsin
regulation and that hypopigmented animals have either an improper input
to the photostasis mechanism or that the photostasis mechanism is
defective.
The effects of histamine on rat and monkey retinal ganglion cells
Authors: GASTINGER MATTHEW J. , YUSUPOV RAFAIL G. , GLICKMAN RANDOLPH D. , MARSHAK DAVID W.
Published: February 2005

Mammalian retinas receive input from the posterior hypothalamus, and the neurotransmitter in this pathway is histamine. To determine whether histamine influences ganglion cells, we analyzed the effects of histamine on their maintained and light-evoked activityin vitro. In monkeys, histamine increased the maintained firing rate in 42% of ganglion cells, decreased it in 38%, and had no effect in 20%. When histamine and the HR3 agonist, methylhistamine, were applied to the same cells in succession, their effects were sometimes different, a finding suggesting that at least one other histamine receptor is present. In addition, the responses of some ganglion cells to full-field light stimuli were decreased by histamine and methylhistamine. In rats, the effects of histamine were somewhat different. Histamine increased the maintained firing rate of 82% of ganglion cells. Methylhistamine and the HR2 agonist, dimaprit, had the same effects as histamine. In some cells, histamine increased the light responses, but in others it decreased them. Histamine had no effect on ganglion cells in either species when synaptic transmission was blocked by low Ca2+/high Mg2+Ames medium. Thus, the major effects of histamine were on the maintained activity of retinal ganglion cells. In both rats and monkeys, 80% or more of the ganglion cells were affected by histamine, and these responses were mediated by at least two of the histamine receptor subtypes.
Testing wave packet dynamics in computing radiative association cross sections
Authors: Martinazzo Rocco , Tantardini Gian Franco
Published: February 2005

A time-dependent wave packet method is used to compute cross sections for radiative recombination reactions using the Li(S2)+H+→LiH+(XΣ+2)+γ as a test case. Cross sections are calculated through standard time-to-energy mapping of the time-dependent transition moment and a useful method is introduced to deal with the low collision energy regime. Results are in quantitative agreement over the whole energy range 10−4–5eV with previous time-independent results for the same system [I. Baccarelli, L. Andric, T. Grozdanov, and R. McCarroll, J. Chem. Phys. 117, 3013 (2002)], thereby suggesting that the method can be of help in computing radiative association cross sections for more complicated systems.
Structure and energetics of small gold nanoclusters and their positive ions
Authors: Walker A. V.
Published: February 2005

We performed density functional theory calculations at the PW91PW91/LANL2DZ, PW91PW91/Stuttgart 1997, PW91PW91/CRENBL, B3LYP/LANL2DZ, and SVWN5/LANL2DZ levels of theory to attain the minimum-energy structures of neutral and cationic gold clusters of up to nine gold atoms. We locate the 2D-to-3D (two-dimensional to three-dimensional) transition in cationic clusters as occurring between Au8+ and Au9+. We also demonstrate that we can correlate the 2D-to-3D transition in cationic clusters with a linear extrapolation of the energy differences of the lowest-lying 2D and 3D structures of cluster sizes below the transition. We then use the same approach to predict that the 2D-to-3D transition occurs in neutral clusters at Au11; this is confirmed by locating 3D Au11 structures that are lower in energy than the best 2D structures reported to date. We examine the effects of choice of basis sets and exchange-correlation functionals on the relative stabilities and other properties of the calculated structures. Finally we find that there is good agreement between calculated and experimental data for clusters with up to six constituent atoms. For clusters with more than seven atoms, there are significant differences observed between the calculated and experimental properties using SVWN5/LANL2DZ, but there is still good agreement for the other levels of theory used.
Nonequilibrium energy dissipation at the interface of sliding model hydroxylated α-alumina surfaces
Authors: Mazyar Oleg A. , Xie Hongwei , Hase William L.
Published: February 2005

Nonequilibrium molecular dynamics simulations were performed to study the dynamics of energy transfer at the interface of a small nanoscale hydroxylated α-alumina surface sliding across a much larger surface of the same material. Sliding velocities of 0.05, 0.5, 5, and 50m∕s and loads of 0, 0.0625, 5, 15, 25, and 100 nN were considered. Nonequilibrium energy distributions were found at the interface for each of these conditions. The velocity distribution P(v) for the atoms in a sublayer of the smaller surface oscillates during the sliding, reflecting the periodicity of the interfacial intermolecular potential. When averaged over the sliding, this P(v) for each of the sublayers is bimodal with Boltzmann and non-Boltzmann components. The non-Boltzmann component, with temperatures in excess of 1000 K and as high as 2500 K, is most important for the interfacial H-atom sublayer and becomes less important in moving to a sublayer further from the interface. Similarly, the temperature of the Boltzmann component decreases for sublayers further from the interface and approaches the 300 K temperature of the boundary. The temperature of the Boltzmann component decreases, but the importance of the non-Boltzmann component increases, as the sliding velocity is decreased. The temperature of the non-Boltzmann component is relatively insensitive to the sliding velocity. Friction forces are determined by calculating the energy dissipation during the sliding, and different regimes are found for variation in the friction force versus sliding velocity vs and applied load. For vs of 0.05, 0.5, and 5m∕s, the friction force is inversely proportional to vs reflecting the increased time for energy dissipation as vs is decreased.
Spin-exchange optically pumped polarized He3 target for low-energy charged particle scattering experiments
Authors: Katabuchi T. , Buscemi S. , Cesaratto J. M. , Clegg T. B. , Daniels T. V. , Fassler M. , Neufeld R. B. , Kadlecek S.
Published: February 2005

We have constructed, tested, and calibrated a polarized He3 target system which facilitates p-He3 elastic scattering at proton energies as low as 2MeV. This system consists of a target cell placed in a uniform B field inside a scattering chamber and an external optical pumping station utilizing Rb spin exchange. Computer-controlled valves allow polarized He3 gas to be transferred quickly between the optical pumping station and the spherical Pyrex target cell, which has Kapton film covering apertures for the passing beam and the scattering particles. The magnetic field required to maintain He3 polarization in the target cell is created with a compact, shielded sine-theta coil. Target gas polarimetry is accomplished using nuclear magnetic resonance and calibrated using the known analyzing power of α-He3 scattering.
Phase measurement algorithm without phase jump
Authors: Seo Seong-Heon , Park M. K. , Lee T. G.
Published: February 2005

A phase comparator provides two outputs proportional to the cosine and sine of the input phase difference. A new algorithm is devised which calculates the phase from the comparator outputs without a phase jump and without the limit of 2π. Instead of calculating the absolute phase at a given time, it calculates the relative phase differences between two subsequent measurements and accumulates them to get the absolute phase. The phase jump can be avoided if the sampling time is selected fast enough that the phase variation does not exceed 2π during the sampling period.
Interferometric measurement of the tip oscillation amplitude in apertureless near-field optical microscopy
Authors: Gucciardi Pietro Giuseppe , Bachelier Guillaume , Mlayah Adnen , Allegrini Maria
Published: February 2005

We have implemented an optical homodyne interferometer to measure the tip oscillation amplitude in apertureless near-field optical microscopy. The setup is fully embedded in the microscope’s design, avoiding the presence of external arms. Our method is based on the synchronous detection of the interference between the fields reflected by the tip and a glass sample surface, while scanning the tip–sample distance over a few wavelengths. With the help of a simple model, we show how the different interference terms arising at frequencies multiple of the tip oscillation can be exploited to easily achieve sub-Ångstrom resolution.
Coupling of the cortical hemodynamic response to cortical and thalamic neuronal activity
Authors: Devor Anna , Ulbert Istvan , Dunn Andrew K. , Narayanan Suresh N. , Jones Stephanie R. , Andermann Mark L. , Boas David A. , Dale Anders M.
Published: February 2005

Accurate interpretation of functional MRI (fMRI) signals requires knowledge of the relationship between the hemodynamic response and the neuronal activity that underlies it. Here we address the question of coupling between pre- and postsynaptic neuronal activity and the hemodynamic response in rodent somatosensory (Barrel) cortex in response to single-whisker deflection. Using full-field multiwavelength optical imaging of hemoglobin oxygenation and electrophysiological recordings of spiking activity and local field potentials, we demonstrate that a point hemodynamic measure is influenced by neuronal activity across multiple cortical columns. We demonstrate that the hemodynamic response is a spatiotemporal convolution of the neuronal activation. Therefore, positive hemodynamic response in one cortical column might be explained by neuronal activity not only in that column but also in the neighboring columns. Thus, attempts at characterizing the neurovascular relationship based on point measurements of electrophysiology and hemodynamics may yield inconsistent results, depending on the spatial extent of neuronal activation. The finding that the hemodynamic signal observed at a given location is a function of electrophysiological activity over a broad spatial region helps explain a previously observed increase of local vascular response beyond the saturation of local neuronal activity. We also demonstrate that the oxy- and total-hemoglobin hemodynamic responses can be well approximated by space–time separable functions with an antagonistic center-surround spatial pattern extending over several millimeters. The surround “negative” hemodynamic activity did not correspond to observable changes in neuronal activity. The complex spatial integration of the hemodynamic response should be considered when interpreting fMRI data.
Conservation and Divergence of Circadian Clock Operation in a Stress-Inducible Crassulacean Acid Metabolism Species Reveals Clock Compensation against Stress
Authors: Boxall Susanna F. , Foster Jonathan M. , Bohnert Hans J. , Cushman John C. , Nimmo Hugh G. , Hartwell James
Published: February 2005

One of the best-characterized physiological rhythms in plants is the circadian rhythm of CO2 metabolism in Crassulacean acid metabolism (CAM) plants, which is the focus here. The central components of the plant circadian clock have been studied in detail only in Arabidopsis (Arabidopsis thaliana). Full-length cDNAs have been obtained encoding orthologs of CIRCADIAN CLOCK-ASSOCIATED1 (CCA1)/LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION1 (TOC1), EARLY FLOWERING4 (ELF4), ZEITLUPE (ZTL), FLAVIN-BINDING KELCH REPEAT F-BOX1 (FKF1), EARLY FLOWERING3 (ELF3), and a partial cDNA encoding GIGANTEA in the model stress-inducible CAM plant, Mesembryanthemum crystallinum (Common Ice Plant). TOC1 and LHY/CCA1 are under reciprocal circadian control in a manner similar to their regulation in Arabidopsis. ELF4, FKF1, ZTL, GIGANTEA, and ELF3 are under circadian control in C3 and CAM leaves. ELF4 transcripts peak in the evening and are unaffected by CAM induction. FKF1 shows an abrupt transcript peak 3 h before subjective dusk. ELF3 transcripts appear in the evening, consistent with their role in gating light input to the circadian clock. Intriguingly, ZTL transcripts do not oscillate in Arabidopsis, but do in M. crystallinum. The transcript abundance of the clock-associated genes in M. crystallinum is largely unaffected by development and salt stress, revealing compensation of the central circadian clock against development and abiotic stress in addition to the well-known temperature compensation. Importantly, the clock in M. crystallinum is very similar to that in Arabidopsis, indicating that such a clock could control CAM without requiring additional components of the central oscillator or a novel CAM oscillator.
The Potassium Transporter AtHAK5 Functions in K+ Deprivation-Induced High-Affinity K+ Uptake and AKT1 K+ Channel Contribution to K+ Uptake Kinetics in Arabidopsis Roots
Authors: Gierth Markus , Mäser Pascal , Schroeder Julian I.
Published: February 2005

Potassium is an important macronutrient and the most abundant cation in plants. Because soil mineral conditions can vary, plants must be able to adjust to different nutrient availabilities. Here, we used Affymetrix Genechip microarrays to identify genes responsive to potassium (K+) deprivation in roots of mature Arabidopsis (Arabidopsis thaliana) plants. Unexpectedly, only a few genes were changed in their expression level after 6, 48, and 96 h of K+ starvation even though root K+ content was reduced by approximately 60%. AtHAK5, a potassium transporter gene from the KUP/HAK/KT family, was most consistently and strongly up-regulated in its expression level across 48-h, 96-h, and 7-d K+ deprivation experiments. AtHAK5 promoter-β-glucuronidase and -green fluorescent protein fusions showed AtHAK5 promoter activity in the epidermis and vasculature of K+ deprived roots. Rb+ uptake kinetics in roots of athak5 T-DNA insertion mutants and wild-type plants demonstrated the absence of a major part of an inducible high-affinity Rb+/K+ (K  m approximately 15–24 μ  m) transport system in athak5 plants. In comparative analyses, uptake kinetics of the K+ channel mutant akt1-1 showed that akt1-1 roots are mainly impaired in a major transport mechanism, with an apparent affinity of approximately 0.9 mm K+(Rb+). Data show adaptation of apparent K+ affinities of Arabidopsis roots when individual K+ transporter genes are disrupted. In addition, the limited transcriptome-wide response to K+ starvation indicates that posttranscriptional mechanisms may play important roles in root adaptation to K+ availability in Arabidopsis. The results demonstrate an in vivo function for AtHAK5 in the inducible high-affinity K+ uptake system in Arabidopsis roots.
A Genome-Wide Analysis of the Effects of Sucrose on Gene Expression in Arabidopsis Seedlings under Anoxia
Authors: Loreti Elena , Poggi Alessandra , Novi Giacomo , Alpi Amedeo , Perata Pierdomenico
Published: February 2005

Exogenous sucrose (Suc) greatly enhances anoxia tolerance of Arabidopsis (Arabidopsis thaliana) seedlings. We used the Affymetrix ATH1 GeneChip containing more than 22,500 probe sets to explore the anaerobic transcriptome of Arabidopsis seedlings kept under anoxia for 6 h in presence or absence of exogenous Suc. Functional clustering was performed using the MapMan software. Besides the expected induction of genes encoding enzymes involved in Suc metabolism and alcoholic fermentation, a large number of genes not related to these pathways were affected by anoxia. Addition of exogenous Suc mitigated the effects of anoxia on auxin responsive genes that are repressed under oxygen deprivation. Anoxia-induced Suc synthases showed a lower induction in presence of exogenous Suc, suggesting that induction of these genes might be related to an anoxia-dependent sugar starvation. Anoxic induction of genes coding for heat shock proteins was much stronger in presence of exogenous Suc. Interestingly, a short heat treatment enhanced anoxia tolerance, suggesting that heat shock proteins may play a role in survival to low oxygen. These results provide insight into the effects of Suc on the anoxic transcriptome and provide a list of candidate genes that enhance anoxia tolerance of Suc-treated seedlings.
Factors influencing vascular plant diversity on 22 islands off the coast of eastern North America
Authors: McMaster Robert T.
Published: February 2005

Aim  The influence of physiographic and historical factors on species richness of native and non‐native vascular plants on 22 coastal islands was examined.

Location  Islands off the coast of north‐eastern USA and south‐eastern Canada between 41° and 45° N latitude were studied. Island size ranges from 3 to 26,668 ha. All islands were deglaciated between 15,000 and 11,000 yr bp; all but the four New Brunswick islands were attached to the mainland until rising sea level isolated them between 14,000 and 3800 yr bp.

Methods  Island species richness was determined from floras compiled or revised since 1969. Simple and multiple regression and rank correlation analysis were employed to assess the relative influence of independent variables on species richness. Potential predictors included island area, latitude, elevation, distance from the mainland, distance from the nearest larger island, number of soil types, years since isolation, years since deglaciation, and human population density.

Results  Native vascular plant species richness for the 22 islands in this study is influenced most strongly by island area, latitude, and distance from the nearest larger island; richness increases with island area, but decreases with latitude and distance from the nearest larger island as hypothesized. That a similar model employing distance from the mainland does not meet the critical value of P confirms the importance of the stepping‐stone effect. Habitat diversity as measured by number of soil types is also an important predictor of native plant species richness, but at least half of its influence can be attributed to island area, with which it is correlated. Two historical factors, years since deglaciation and years since isolation, also appear to be highly correlated with native species richness, but their influence cannot be separated from that of latitude for the present sample size. Non‐native vascular plant species richness is influenced primarily by island area and present‐day human population density, although human population density may be a surrogate for the cumulative effect of several centuries of anthropogenic impacts related to agriculture, hunting, fishing, whaling, tourism, and residential development. Very high densities of ground‐nesting pelagic birds may account for the high percentage of non‐native species on several small northern islands.

Main conclusions  Many of the principles of island biogeography that have been applied to oceanic islands apply equally to the 22 islands in this study. Native vascular plant species richness for these islands is strongly influenced by physiographic factors. Influence of two historical factors, years since deglaciation and years since isolation, cannot be assessed with the present sample size. Non‐native vascular plant species richness is influenced by island area as well as by human population density; human population density may be a surrogate for other anthropogenic impacts.
Landscape context of sheetweb spider (Araneae: Linyphiidae) abundance in cereal fields
Authors: Schmidt Martin H. , Tscharntke Teja
Published: February 2005

Aim  Sheetweb spiders (Araneae: Linyphiidae, subfamily Linyphiinae) exemplify a highly mobile group of farmland arthropods with very variable abundances in crops within and between years. Despite their dominance in crops during summer, they overwinter predominantly in perennial non‐crop habitats, and their densities in crops during spring should therefore depend on the amount of favourable overwintering habitat in the surrounding landscape. We tested the effect of landscape composition on sheetweb spider abundance with special attention to the range of their aerial dispersal and weather dependence.

Location  The study was carried out in 18 non‐overlapping landscape sectors of 3 km radius around the city of Göttingen (Germany), forming a gradient from structurally simple, with up to 85% arable land, to structurally complex, with high percentages of grassland and other non‐crop habitats.

Methods  Sheetweb spider abundances in winter wheat fields were sampled during May and June 2001–2003 with a distance method. They were related to landscape composition at 11 spatial scales between 95 and 3000 m radius around the study sites.

Results  In 2001 and 2003, spider abundances were enhanced by high percentages of non‐crop habitats in 1–3 km circumference (e.g. from 18 to 130 m−2 in late May 2001), and multiplied during consecutive sampling periods (e.g. from on average 36 to 131 m−2 between mid‐May and late June 2001). Spider abundances were constantly low and unrelated to the landscape context in 2002. In that year, immigration appeared to be inhibited by factors connected to exceptionally high amounts of rain during May.

Main conclusions  Sheetweb spiders responded to landscape composition up to several kilometres away and the effects varied between years, demonstrating the need to consider large space and time‐scales to understand their population dynamics. Semi‐natural habitats should be preserved to enhance these important natural enemies of crop pests in agricultural landscapes.
Cytokinin and the regulation of a tobacco metallothionein‐like gene during copper stress
Authors: Thomas John C. , Perron Mike , LaRosa P. Christopher , Smigocki Ann C.
Published: February 2005

Higher plant metallothioneins are suspected of reducing metal‐induced oxidative stress and binding copper and zinc cofactor metals for delivery to important apometalloproteins. A metallothionein‐like gene (MT‐L2) cDNA clone pCkn16A1 (Accession U35225) was cloned from heat‐shock‐induced Nicotiana plumbaginifolia containing the heat‐shock‐inducible isopentenyl transferase (ipt) gene (HS‐ipt). Ipt expression in plants leads to enhanced cytokinin biosynthesis. In mature leaves of non‐transformed N. plumbaginifolia and Nicotiana tabacum, copper stress caused a significant loss of MT‐L2 mRNA transcripts. Under non‐stressed conditions, HS‐ipt induced (N. plumbaginifolia) or light‐induced (SSU‐ipt) (N. tabacum) plants had higher MT‐L2 transcript levels than non‐transformed or transformed (GUS) controls. Unlike control plants, copper stress did not reduce MT‐L2 mRNA levels in the cytokinin accumulating transgenic plants. Enhanced cytokinin production also led to lower lipid peroxidation compared with controls under non‐stressed and copper‐stressed conditions. Greater MT‐L2 transcript levels and protection against oxidative events prior to or during copper stress could contribute to the observed eight‐fold accumulation of copper in mature leaves of ipt expressing plants compared to non‐transformed plants. Expression of this tobacco MT‐L2 mRNA may be modulated directly by cytokinin or indirectly as a consequence of cytokinin‐mediated antioxidant activity.
Glycolate metabolism in green algae
Authors: Stabenau Helmut , Winkler Uwe
Published: February 2005

Using 14C‐labelled substrates, the succession of the single steps in the glycolate metabolism was investigated in Mougeotia scalaris and Eremosphaera viridis, which, within the group of green algae, are representatives of the evolutionary lines of Charophyta and Chlorophyta, respectively. In both algae the same metabolites are formed as in higher plants, although in Eremosphaera, which in contrast to Mougeotia does not possess leaf peroxisomes, all reactions are exclusively mitochondrial. Concomitant with the oxidation of glycolate, the synthesis of ATP was demonstrated in Eremosphaera. Formation of tartronic semi‐aldehyde or other products different from those in land plants could not be demonstrated in either of these algae. Excretion of glycolate by Mougeotia and Eremosphaera is enhanced by decreasing the CO2 concentration as well as by increasing the light intensity, but is completely stopped about 14 h later. Whereas increasing enzyme activities of the glycolate pathway apparently reduces glycolate excretion in Mougeotia, activation of CO2 pumps seems to be the dominant reaction to prevent glycolate excretion in Eremosphaera. Mesostigma viride is one of the phylogenetically oldest algae in the group of Charophyceae. As this alga has already been demonstrated to contain microbodies with enzymes of leaf peroxisomes, the peroxisomal glycolate pathway must have originated at a very early stage. Surprisingly, the organelles from Mesostigma contain also the glyoxysomal marker enzyme isocitrate lyase suggesting these microbodies to be prototypes from which both glyoxysomes and leaf peroxisomes evolved.
Salt stress and glycolytic regulation in suspension‐cultured cells of the mangrove tree, Bruguiera sexangula
Authors: Suzuki Mihoko , Hashioka Aya , Mimura Tetsuro , Ashihara Hiroshi
Published: February 2005

Suspension‐cultured cells derived from seedlings of Bruguiera sexangula are tolerant to NaCl. To examine the influence of long‐term salt stress on glycolysis, we determined the effect of 100 mM NaCl on the activities of two key enzymes, phosphofructokinase (PFK, EC 2.7.1.11) and pyruvate kinase (PK, EC 2.7.1.40), and on the bypass enzymes, pyrophosphate: fructose‐6‐phosphate phosphotransferase (PFP, EC 2.7.1.90), phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.49) and phosphoenolpyruvate phosphatase (PEPase, EC 3.1.3.60). From 10 days after NaCl treatment, increases were found in the activities of PFK, PK and PEPC. In contrast, there was little or no difference in the activities of PFP or PEPase. The short‐term effect of salt stress was also investigated. NaCl (150 mM) caused a 1.4‐fold increase in respiratory O2 uptake at 24 h after treatment. Alongside this respiratory rise, drastic changes in the levels of glycolytic metabolites were found: a decrease in the levels of glucose, glucose‐6‐phosphate and fructose‐6‐phosphate, and an increase in the levels of fructose‐1, 6‐bisphosphate and metabolites of the later steps of the glycolytic pathway. The crossover diagram of metabolites suggests that NaCl stimulates those steps catalysed by PFK and/or PFP. The in vitro activities of partially purified PFK and PFP were increased by the addition of 150 mM NaCl. The effect of salt on the kinetic properties of PFK and PFP was studied, and possible control mechanisms of glycolysis on salt stress are discussed.
The response of nodulated alfalfa to water supply, temperature and elevated CO2: photosynthetic downregulation
Authors: Aranjuelo Iker , Pérez Pilar , Hernández Libia , Irigoyen Juan José , Zita Gloria , Martínez‐Carrasco Rafael , Sánchez‐Díaz Manuel
Published: February 2005

Plants grown in an environment of elevated CO2 and temperature often show reduced CO2 assimilation capacity, providing evidence of photosynthetic downregulation. The aim of this study was to analyse the downregulation of photosynthesis in elevated CO2 (700 µmol mol−1) in nodulated alfalfa plants grown at different temperatures (ambient and ambient + 4°C) and water availability regimes in temperature gradient tunnels. When the measurements were taken in growth conditions, a combination of elevated CO2 and temperature enhanced the photosynthetic rate; however, when they were carried out at the same CO2 concentration (350 and 700 µmol mol−1), elevated CO2 induced photosynthetic downregulation, regardless of temperature and drought. Intercellular CO2 concentration measurements revealed that photosynthetic acclimation could not be accounted for by stomatal limitations. Downregulation of plants grown in elevated CO2 was a consequence of decreased carboxylation efficiency as a result of reduced rubisco activity and protein content; in plants grown at ambient temperature, downregulation was also induced by decreased quantum efficiency. The decrease in rubisco activity was associated with carbohydrate accumulation and depleted nitrogen availability. The root nodules were not sufficiently effective to balance the source–sink relation in elevated CO2 treatments and to provide the required nitrogen to counteract photosynthetic acclimation.
Characterization of tomato fruit ripening and analysis of gene expression in F1 hybrids of the ripening inhibitor (rin) mutant
Authors: Kitagawa Mamiko , Ito Hirotaka , Shiina Takeo , Nakamura Nobutaka , Inakuma Takahiro , Kasumi Takafumi , Ishiguro Yukio , Yabe Kimiko , Ito Yasuhiro
Published: February 2005

The ripening inhibitor (rin) mutation of tomato yields non‐ripening fruit, and the gene corresponding to RIN, LeMADS‐RIN, is known to encode a transcriptional factor that controls ripening‐related genes. In this study, to evaluate the heterozygosity effect of rin on fruit ripening, we developed eight F1 hybrid lines of the rin mutant from various crosses between the lines of the rin mutant and wild type. In the fruit of these F1 hybrid lines, the shelf‐life was improved, but both the shelf‐life and colouring varied between the lines. We then chose one line of the F1 hybrids and investigated the physiological and transcriptional properties of the fruit. Compared with the wild‐type parent, this F1 line showed about half the lycopene content, lower fruit softening and lower mRNA accumulation of the genes that encode phytoene synthase (Psy), polygalacturonase (PG), β‐galactosidase (TBG4) and expansin (LeEXP1). The characteristic climacteric rise in ethylene production typically observed in the wild‐type parent during fruit maturation was not observed in the fruit of this F1 line. The genes that encode ethylene biosynthetic enzymes, namely 1‐aminocyclopropane‐1‐carboxylic acid (ACC) synthase (ACS2 and ACS4) and ACC oxidase (ACO1), were, however, significantly expressed in the F1 hybrid, suggesting that the post‐transcriptional regulator for activating these enzymes is affected by LeMADS‐RIN. These results suggest that the heterologous effect of LeMADS‐RIN in F1 hybrids affects the gene transcription and activation of ripening‐related factors, resulting in changes in fruit properties, including the extension of the shelf‐life.
Evaluation of the Suitability of Monoclonal Antibodies for Flow Cytometric Intracellular Cytokine Detection in Porcine Peripheral Blood Lymphocytes
Authors: Sipos W. , Willheim M. , Hofbauer G. , Pietschmann P.
Published: February 2005

Panels of monoclonal antibodies (mAbs) specific for porcine interleukin (IL)‐2, IL‐4, IL‐6, IL‐12, interferon (IFN)‐γ and tumour necrosis factor (TNF)‐α were evaluated for their applicability in flow cytometric intracellular cytokine detection. Peripheral blood mononuclear cells were short‐time stimulated in the presence of brefeldin‐A, ionomycin and phorbol‐12‐myristate‐13‐acetate, fixed and incubated with the respective mAbs as well as phycoerythrin‐conjugated second‐step antibodies. Suitability of mAbs was judged by use of statistical data and by visual control of scattergrams, considering the capability of mAbs to discriminate between cytokine‐positive and cytokine‐negative cell populations. The number of suitable clones differed to a high degree between the investigated cytokines, but at least one mAb fitting for flow cytometric intracellular cytokine detection could be identified within each panel. Monoclonal Abs producing scattergrams with a clear demarcation between positive and negative cell populations were found within the anti‐IL‐2, IL‐6 and IFN‐γ panels, whereas less well defined positive and negative cell populations could be generated by use of mAbs within the anti‐IL‐4 and TNF‐α panels. Only one moderately fitting mAb was identified within the anti‐IL‐12 panel. After having evaluated the best fitting mAbs, these were used to obtain reference levels for the physiological range of porcine lymphocytic cytokine production in a second set of experiments. For that reason, 13 clinically healthy pigs aged between 6 weeks and 6 months were investigated. Data presented are given as mean ± SD of the percentage of positive‐staining lymphocytes: IL‐2, 45.5 ± 27.6; IL‐4, 34.1 ± 21.3; IL‐6, 45.4 ± 23.8; IL‐12, 13.9 ± 8.6; TNF‐α, 43.4 ± 11.3; IFN‐γ, 65.5 ± 14.8.
Morbillivirus Infections in Aquatic Mammals: A Brief Overview
Authors: Guardo G. Di , Marruchella G. , Agrimi U. , Kennedy S.
Published: February 2005

Since 1987, at least eight morbillivirus infection (MI) epidemics have caused mass mortality of several free‐living pinniped and cetacean populations around the world. The responsible agents, all belonging to the genus Morbillivirus (family Paramyxoviridae), have been characterized as either ‘canine distemper virus’ strains, infecting pinnipeds, or as three new morbilliviruses, namely ‘phocid (phocine) distemper virus’ , ‘porpoise morbillivirus’ and ‘dolphin morbillivirus’ . The last two agents are currently gathered under the common denomination of ‘cetacean morbillivirus’. At post‐mortem examination, a commonly occurring macroscopic lesion is represented by more or less severe bilateral pneumonia, with consolidation, congestion and oedema of both lungs, which fail to collapse. Histologically, a non‐suppurative broncho‐interstitial pneumonia, characterized by type II pneumocyte hyperplasia and by formation of endobronchial, endobronchiolar and endoalveolar ‘Warthin–Finkeldey type’ syncytia, as well as a multifocal, non‐suppurative encephalitis, associated with a severe and generalized lymphoid tissue depletion, are common pathological findings. Furthermore, eosinophilic viral inclusions are often detected, at both the intracytoplasmic and intranuclear level, within bronchial and bronchiolar epithelial, pulmonary syncytial, neuronal and other cell types. These inclusions, along with lymphoid and other cellular elements, are often found to be immunohistochemically positive for morbillivirus antigen. Among the still debated, or even controversial issues regarding MI in sea mammals, the one related to the origin of their causative agents is of particular concern. Another intriguing issue regards the synergistic effects, if any, associated with chronic exposure to a number of environmental pollutants, such as organochlorines and heavy metals. In fact, it is also unknown whether and how these chemicals contribute towards modulating the pathogenic and pathogenetic activity primarily displayed by sea mammal morbilliviruses.