Effects of common soil anions and pH on the uptake and accumulation of perchlorate in lettuce

A mechanistic understanding of perchlorate () entry into plants is important for establishing the human health risk associated with consumption of contaminated produce and for assessing the effectiveness of phytoremediation. To determine whether common soil anions affect uptake and accumulation in higher plants, a series of competition experiments using lettuce (Lactuca sativa L.) were conducted between (50 nM) and (4–12 mM), (1–10 mM), or Cl⁻ (5–15 mM) in hydroponic solution. The effects of (0–5 mM) and pH (5.5–7.5) on uptake were also examined. Increasing in solution significantly reduced the amount of taken up by green leaf, butter head, and crisphead lettuces. Sulfate and Cl⁻ had no significant effects on uptake in lettuce over the concentrations tested. Increasing pH significantly reduced the amount of taken up by crisphead and green leaf lettuces, whereas increasing significantly reduced uptake in butter head lettuce. The inhibition by across all lettuce genotypes suggests that may share an ion carrier with , and the decrease in uptake with increasing pH or provides macroscopic evidence for cotransport across the plasma membrane.     

Cell-to-cell pathway dominates xylem-epidermis hydraulic connection in<Emphasis Type="Italic"> Tradescantia fluminensis</Emphasis> (Vell. Conc.) leaves

A steady supply of water is indispensable for leaves to fulfil their photosynthetic function. Understanding water movement in leaves, especially factors that regulate the movement of water flux from xylem to epidermis, requires that the nature of the transport pathway be elucidated. To determine the hydraulic linkage between xylem and epidermis, epidermal cell turgor pressure (P _t) in leaves of Tradescantia fluminensis was monitored using a cell pressure probe in response to a 0.2 MPa step change in xylem pressure applied at the leaf petiole. Halftime of P _t changes were 10–30 times greater than that of water exchange across an individual cell membrane suggesting that cell-to-cell water transport constitutes a significant part of the leaf hydraulic path from xylem to epidermis. Furthermore, perfusion of H₂O₂ resulted in increases of both and by a factor of 2.5, indicating that aquaporins may play a role in the xylem to epidermis hydraulic link. The halftime for water exchange did not differ significantly between cells located at the leaf base (2.5 s), middle (2.6 s) and tip (2.5 s), indicating that epidermal cell hydraulic properties are similar along the length of the leaf. Following the pressure application to the xylem (0.2 MPa), P _t changed by 0.12, 0.06 and 0.04 MPa for epidermal cells at the base, middle and the tip of the leaf, respectively. This suggests that pressure dissipation between xylem and epidermis is significant, and that the pressure drop along the vein may be due to its structural similarities to a porous pipe, an idea which was further supported by measurements of xylem hydraulic resistance using a perfusion technique.     

The Influence of Hydroregime on Catch, Abundance And Recruitment of the Catfish, Chrysichthys Nigrodigitatus (Bagridae) and the Bonga, Ethmalosa Fimbriata (Clupeidae) of Southeastern Nigeria's Inshore Waters

This paper investigates the relationship between the hydroclimatic parameters (rainfall and flood index) and the catch, stock abundance and recruitment of the catfish, Chrysichthys nigrodigitatus (Bagridae) and the bonga, Ethmalosa fimbriata (Clupeidae) of southeastern Nigeria's inshore waters. For C. nigrodigitatus, most peaks in the mean biomass and recruitment curves occurred during the 'wet' years, i.e., years for which the percentage deviations of rainfall and flood index from their means remained above their averages. Catch and abundance respectively showed good positive linear correlation with the flood index. E. fimbriata behaved differently; some peaks in the and curves occurred in the 'wet' and some in the 'dry' years; and there was no correlation between the annual catch of bonga and either the rainfall or the flood index. The hypothesis, that linear relationships exist between the interannual variations in the hydroregime and the yearly fluctuations in the catch and population structure of some coastal and estuarine fishes, holds true for the catfish, C. nigrodigitatus, but not for bonga, E. fimbriata.     

The mechanism and kinetics of decomposition of 5-aminotetrazole

The pathway and ab initio direct kinetics of the decomposition 5-aminotetrazole (5-ATZ) to HN₃ and NH₂CN was investigated. Reactant, products and transition state were optimized with MP2 and B3LYP methods using 6–311G** and aug-cc-pVDZ basis sets. The intrinsic reaction coordinate curve of the reaction was calculated using the MP2 method with 6–311G** basis set. The energies were refined using CCSD(T)/6–311G**. Rate constants were evaluated by conventional transition-state theory (CVT) and canonical variational transition-state theory (TST), with tunneling effect over 300 to 2,500 K. The results indicated that the tunneling effect and the variational effect are small for the calculated rate constants. The fitted three-parameter expression calculated using the CVT and TST methods are and , respectively. Figure The mechanism of the decomposition process of 5-ATZ to HN₃ and NH₂CN     

Phase Transitions of Frozen Camu-camu (Myrciaria dubia (H.B.K.) McVaugh) Pulp: Effect of Cryostabilizer Addition

Camu-camu is a tropical fruit with very high vitamin C content and commercialized as frozen pulp. Enthalpies of freezing, temperatures of the onset of ice melting, and glass transition temperatures of the maximally freeze-concentrated phase () of camu-camu pulp and of samples containing maltodextrin (DE20) and sucrose were measured by differential scanning calorimetry. Maltodextrin exhibited the largest freeze stabilization potential, increasing from −58.2 °C (natural pulp) to −39.6 °C when 30% (w/w) maltodextrin DE 20 was added. Sucrose showed negligible effect on but enhanced considerably the freezing point depression and less amount of ice was formed.     

Theoretical study of AlH(2+)n (n=1-7) dications

The structures and stability of 1–7 dications were calculated at the ab initio MP2/aug-cc-pVTZ level of theory. The dications AlH²⁺ 1 and 2 were characterized to be unstable thermodynamically. However, these and the stable dications, 3–7 have considerable kinetic barriers for deprotonation. Each of the structures 3–7 contains one or more two-electron three-center (2e–3c) bonds. Aluminum atoms of these dications carry most of the positive charges, as indicated by NBO charge calculations.Dedicated to Professor Dr. Paul von Ragué Schleyer on the occasion of his 75th birthday     

Nitrogen metabolism of asparagine and glutamate in Vero cells studied by <Superscript>1</Superscript>H/<Superscript>15</Superscript>N NMR spectroscopy

Glutamine-free culture of Vero cells has previously been shown to cause higher cell yield and lower ammonia accumulation than that in glutamine-containing culture. Nitrogen metabolism of asparagine and glutamate as glutamine replacer was studied here using nuclear magnetic resonance (NMR) spectroscopy. ¹⁵N-labelled glutamate or asparagine was added and their incorporation into nitrogenous metabolites was monitored by heteronuclear multiple bond coherence (HMBC) NMR spectroscopy. In cells incubated with l-[¹⁵N]glutamate, the ¹⁵N label was subsequently found in a number of metabolites including alanine, aspartate, proline, and an unidentified compound. No detectable signal occurred, indicating that glutamate was utilized by transamination rather than by oxidative deamination. In cells incubated with l-[2-¹⁵N]asparagine, the ¹⁵N label was subsequently found in aspartate, the amine group of glutamate/glutamine, and in two unidentified compounds. Incubation of cells with l-[4-¹⁵N]asparagine showed that the amide nitrogen of asparagine was predominantly transferred to glutamine amide. There was no detectable production of , showing that most of the asparagine amide was transaminated by asparagine synthetase rather than deaminated by asparaginase. Comparing with a glutamine-containing culture, the activities of phosphate-activated glutaminase (PAG), glutamate dehydrogenase (GDH) and alanine aminotransferase (ALT) decreased significantly and the activity of aspartate aminotransferase (AST) decreased slightly.     

Use of isotopic signatures to assess the food web in a tropical shallow marine ecosystem of Southeastern Brazil

A dual isotope approach was used to assess the relative importance of terrestrial vegetation detritus and other primary producers in the trophic web of Flamengo Sound (Ubatuba, SP), SE Brazil, surrounded by the Atlantic Rain Forest. Primary producers showed distinct C signatures and the observed values suggest that little terrestrial or bulk sediment organic matter enter the food web of the sound. Suspended particulate organic matter (POM, supports the bulk of the consumers, with some contribution by macroalgae . Consumers C values ranged from −17.4 to . At least three trophic levels were detectable in the food web. The N value of POM was , while that of sediment and detritus was . The N values of suspension feeding benthic invertebrates were 8.2–, deposit feeders 8.3–, and carnivores 10.7–. Values for fishes were for detritivore, 11.4– for benthic feeders, 12.4– for zooplanktivores, and for piscivores/benthic invertebrate feeders. Squid mean value was . There is a reasonable agreement between feeding habits information from the literature and N values from this study. In the sound, the first and second trophic steps seem to be about 1– higher than those of similar organisms studied in temperate waters and this may reflect an input of allochtonous anthropogenic nitrogen enriched in ¹⁵N from human activities.     

Seven new species of Eimeria Schneider, 1875 (Apicomplexa: Eimeriidae) from colubrid snakes of Guatemala and a discussion of what to call ellipsoid tetrasporocystic, dizoic coccidia of reptiles

During a survey of Guatemalan herpetofauna in the summers of 1998–2000, 29 presumed new species of Eimeria Schneider, 1875 were found, seven of which have a distinct elongate-ellipsoidal shape (L/W ratio ≥ 1.7) and are described herein. Six of the seven new species are similar in oöcyst length, width and L/W ratio and sporocyst length, width and L/W ratio, lack a micropyle, oöcyst residuum, Stieda body, sub- and parastieda bodies, have a polar granule and sporocyst residuum, and their sporocysts appear to have dehiscence sutures. The seventh is slightly smaller and has sporocysts with a Stieda body. The new species are: E. coniophanes n. sp – whose sporulated oöcysts from Coniophanes fissidens are 29.2×14.9 (27–31×13–16) m, with sporocysts m; E. coniophis n. sp. –from Conophis lineatus are 32.0×16.5 (30–34×14–18) m, with sporocysts m; E. dryomarchoni n. sp. – from Drymarchon corais are 32.2×17.7 (31–34×17–19) m, with sporocysts m; E. leptophis n. sp. – from Leptophis mexicanus are 29.5×17.0 (28–31×16–18) m, with sporocysts m; E. oxybelis n. sp. – from Oxybelis aeneus are 31.8×16.5 (29–33×15–18) m, with sporocysts m; and E. scaphiodontophis n. sp. – from Scaphiodontophis annulatus are 30.0×15.3 (28–33×14–16) m, with sporocysts m. Sporulated oöcysts of E. siboni n. sp. from Sibon nebulata are 24.3×14.2 (21–27×13–16) m, with sporocysts m and with a Stieda body. We conclude that until all aspects of each life-cycle are known, it is prudent at this time to name all tetrasporocystic dizoic coccidia from snakes as members of Eimeria rather than place some of them in Choleoeimeria Paperna & Landsberg, 1989.     

Complexation of oxoanions and cationic metals by the biscatecholate siderophore azotochelin

Azotochelin is a biscatecholate siderophore produced by the nitrogen-fixing soil bacterium Azotobacter vinelandii. The complexation properties of azotochelin with a series of oxoanions [Mo(VI), W(VI) and V(V)] and divalent cations [Cu(II), Zn(II), Co(II) and Mn(II)] were investigated by potentiometry, UV–vis and X-ray spectroscopy. Azotochelin forms a strong 1:1 complex with molybdate (log K = 7.6 ± 0.4) and with tungstate and vanadate; the stability of the complexes increases in the order Mo < V < W (log K _app^Mo = 7.3 ± 0.4; log K _app^V = 8.8 ± 0.4 and log K _app^W = 9.0 ± 0.4 at pH 6.6). The Mo atom in the 1:1 Mo–azotochelin complex is bound to two oxo groups in a cis position and to the two catecholate groups of azotochelin, resulting in a slightly distorted octahedral configuration. Below pH 5, azotochelin appears to form polynuclear complexes with Mo in addition to the 1:1 complex. Azotochelin also forms strong complexes with divalent metals. Of the metals studied, Cu(II) binds most strongly to azotochelin , followed by Zn(II) , Mn(II) and Co(II) . Since very few organic ligands are known to bind strongly to oxoanions (and particularly molybdate) at circumneutral pH, the unusual properties of azotochelin may be used for the separation and concentration of oxoanions in the laboratory and in the field. In addition, azotochelin may prove useful for the investigation of the biogeochemistry of Mo, W and V in aquatic and terrestrial systems. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

A bias correction for estimates of effective population size based on linkage disequilibrium at unlinked gene loci*

Analysis of linkage disequilibrium (=mean squared correlation of allele frequencies at different gene loci) provides a means of estimating effective population size (N _e) from a single sample, but this method has seen much less use than the temporal method (which requires at least two samples). It is shown that for realistic numbers of loci and alleles, the linkage disequilibrium method can provide precision comparable to that of the temporal method. However, computer simulations show that estimates of N _e based on for unlinked, diallelic gene loci are sharply biased downwards ( in some cases) if sample size (S) is less than true N _e. The bias is shown to arise from inaccuracies in published formula for when S and/or N _e are small. Empirically derived modifications to for two mating systems (random mating and lifetime monogamy) effectively eliminate the bias (residual bias in % in most cases). The modified method also performs well in estimating N _e in non-ideal populations with skewed sex ratio or non-random variance in reproductive success. Recent population declines are not likely to seriously affect , but if N has recently increased from a bottleneck can be biased downwards for a few generations. These results should facilitate application of the disequilibrium method for estimating contemporary N _e in natural populations. However, a comprehensive assessment of performance of with highly polymorphic markers such as microsatellites is needed.The US Governmentȁ9s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.     

Genetic structure of an insect-pollinated and bird-dispersed tropical tree in vegetation fragments and corridors: implications for conservation

In the vegetation corridors that connect small remnants of undisturbed primary forest in the Lavras landscape (Brazil), Protium spruceanum is a representative of a mass-flowering insect-pollinated and bird-dispersed tree. Allozyme variation was quantified from five forest remnants (N = 150) from secondary vegetation corridors linking them (N = 80) to generate information for genetic conservation. The species adhered to H-W equilibrium in all fragments in most of the loci. The results indicated high gene diversity in the fragments and corridors positively correlated with the plant density (r = 0.742, R ² = 0.551, d.f. = 4). We did not find evidence of inbreeding within fragments nor overall The genetic differentiation among remnants was low Evidence of recent bottlenecks by anthropogenic disturbance was detected in fragments (P < 0.05, Wilcoxon sign-rank test). The minimal viable population was estimated for conservation in situ, indicating fragments with possibilities of maintaining genetic equilibrium diversity in the short term (except F3) and in the long term (only F5). The ratios was also calculated to contribute to vegetation enrichment, area recovery or creation of new vegetation corridors. We found high levels of gene diversity in the vegetation corridors, genetic identity with the fragments and absence of inbreeding. Thus, our results suggest that landscape management strategies should therefore consider both the creation of new vegetation corridors and the protection of extant ones.     

Kinetics and mechanistic studies of the reactions of metleghemoglobin, ferrylleghemoglobin, and nitrosylleghemoglobin with reactive nitrogen species

It is now established that nitrogen monoxide is produced not only in animals but also in plants. However, much less is known about the pathways of generation and the functions of in planta. One of the possible targets of is leghemoglobin (Lb), the hemoprotein found in high concentrations in the root nodules of legumes that establish a symbiosis with nitrogen-fixing bacteria. In analogy to hemoglobin and myoglobin, we have shown that different forms of Lb react not only with , but also with so-called reactive nitrogen species derived from it, among others peroxynitrite and nitrite. Because of the wider active-site pocket, the rate constants measured in this work for and for nitrite binding to metLb are 1 order of magnitude larger than the corresponding values for binding of these species to metmyoglobin and methemoglobin. Moreover, we showed that reactive nitrogen species are able to react with two forms of Lb that are produced in vivo but that cannot bind oxygen: ferrylLb is reduced by and nitrite, and nitrosylLb is oxidized by peroxynitrite. The second-order rate constants of these reactions are on the order of 10², 10⁶, and 10⁵ M⁻¹ s⁻¹, respectively. In all cases, the final reaction product is metLb, a further Lb form that has been detected in vivo. Since a specific reductase is active in nodules, which reduces metLb, reactive nitrogen species could contribute to the recycling of these inactive forms to regenerate deoxyLb, the oxygen-binding form of Lb.     

Dynamics of cardiorespiratory function in Standardbred horses during different intensities of constant-load exercise

Summary Six Standardbred horses were used to evaluate the time course of pulmonary gas exchange, ventilation, heart rate (HR) and acid base balance during different intensities of constant-load treadmill exercise. Horses were exercised at approximately 50%, 75% and 100% maximum oxygen uptake ( max) for 5 min and measurements taken every 30 s throughout exercise. At all work rates, the minute ventilation, respiratory frequency and tidal volume reached steady state values by 60 s of exercise. At 100% max, the oxygen consumption ( ) increased to mean values of approximately 130 ml/kg·min, which represents a 40-fold increase above resting . At the low and moderate work rates, showed no significant change from 30 s to 300 s of exercise. At the high work rate, the mean at 30 s was 80% of the value at 300 s. The HR showed no significant change over time at the moderate work rate but differing responses at the low and high work rates. At the low work rate, the mean HR decreased from 188 beats/min at 30 s to 172 beats/min at 300 s exercise, whereas at the high work rate the mean HR increased from 204 beats/min at 30 s to 221 beats/min at 300 s exercise. No changes in acid base status occurred during exercise at the low work rate. At the moderate work rate, a mild metabolic acidosis occurred which was nonprogressive with time, whereas the high work rate resulted in a progressive metabolic acidosis with a base deficit of 16 mmol/l by 300 s exercise. It is concluded that the kinetics of gas exchange during exercise are more rapid in the horse than in man, despite the relatively greater change in in the horse when going from rest to high intensity exercise.Symbols and abbreviations E minute ventilation - V _T tidal volume - oxygen uptake - carbon dioxide output - oxygen pulse - ventilatory equivalent for oxygen - ventilatory equivalent for carbon dioxide - R respiratory exchange ratio - HR heart rate - SBC standard bicarbonate - STPD standard temperature and pressure dry - BTPS body temperature and pressure saturated - arterial oxygen content - arteriovenous oxygen content difference - Rf respiratory frequency     

Topological research on diamagnetic susceptibilities of organic compounds

A novel molecular connectivity index, , based on the adjacency matrix of molecular graphs and novel atomic valence connectivities, , for predicting the molar diamagnetic susceptibilities of organic compounds is proposed. The is defined as: , where and E_i are the atomic valence connectivity and the valence orbital energy of atom i, respectively. A good QSPR model for molar diamagnetic susceptibilities can be constructed from and using multivariate linear regression (MLR). The correlation coefficient r, standard error, and average absolute deviation of the MLR model are 0.9918, 5.56 cgs, and 4.26 cgs, respectively, for the 721 organic compounds tested (training set). Cross-validation using the leave-one-out method demonstrates that the MLR model is highly reliable statistically. Using the MLR model, the average absolute deviations of the predicted values of molar diamagnetic susceptibility of another 360 organic compounds (test set) is 4.34 cgs. The results show that the current method is more effective than literature methods for estimating the molar diamagnetic susceptibility of an organic compound. The MLR method thus provides an acceptable model for the prediction of molar diamagnetic susceptibilities of organic compounds. Figure Plot of calculated vs experimental values of molar diamagnetic susceptibilities using the multivariate linear regression (MLR) model (Eq. 8)     

Deletion of a 236 kb region around S 4-RNase in a stylar-part mutant S 4 sm -haplotype of Japanese pear

Japanese pear (Pyrus pyrifolia Nakai) has a gametophytic self-incompatibility (GSI) mechanism controlled by a single S-locus with multiple S-haplotypes, each of which contains separate genes that determine the allelic identity of pistil and pollen. The pistil S gene is the S-ribonuclease (S-RNase) gene, whereas good candidates for the pollen S gene are the F-box protein genes. A self-compatible (SC) cultivar, ‘Osa-Nijisseiki’, which is a bud mutant of ‘Nijisseiki’ (S ₂ S ₄), has a stylar-part mutant -haplotype, which lacks the S ₄-RNase gene but retains the pollen S gene. To delineate the deletion breakpoint in the -haplotype, we constructed a bacterial artificial chromosome (BAC) library from an S ₄-homozygote, and assembled a BAC contig of 570 kb around the S ₄-RNase. Genomic PCR of DNA from S ₄- and -homozygotes and the DNA sequence of the BAC contig allowed the identification of a deletion of 236 kb spanning from 48 kb upstream to 188 kb downstream of S ₄-RNase. The -haplotype lacks 34 predicted open reading frames (ORFs) including the S ₄-RNase and a pollen-specific F-box protein gene (termed as S ₄ F-box0). Genomic PCR with a primer pair designed from the deletion junctions yielded a product specific for the -haplotype. The product could be useful as a maker for early selection of SC cultivars harboring the -haplotype. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Long-term changes in nutrient concentrations of the Changjiang River and principal tributaries

We present long-term nutrient data on the Changjiang River (Yangtze River) at six hydrological stations and eight principal tributaries during the period 1958–1985. Three patterns of temporal changes were observed in nitrate and nitrite : minimal variations in the upper catchment area, rapid increases in the middle watershed towards the end of the 1970s, and a gradual increase in the lower drainage basin. Prior to the 1970s, the level of throughout the Changjiang River system remained fairly constant. In the 1980s, however, this changed, with the lowest values in the upper Changjiang changing rapidly to the highest in the middle reaches and then declining slowly but steadily in the lower courses. Compared to and ammonium and soluble reactive phosphorus (SRP) showed smaller increases or no long-term variations, while dissolved silica (DSi) concentration generally decreased at most stations. These three patterns of and changes in the Changjiang River system were reflective of the difference in chemical fertilizer use and landscape features (e.g., slope, soil type and water body area) of the drainage basins of the primary tributaries. The decreases in DSi were most likely attributed to a reduction in suspended sediment loading due to dam constructions and increasing diatom consumption. The increase in and with a reduction in DSi concentrations in the Changjiang River could have significant effects on the stoichiometric balance of nutrients delivered to the East China Sea and the ecosystem in this dynamic region.     

Regional Assessment of N Saturation using Foliar and Root \varvec {\delta}^{\bf 15}{\bf N}

N saturation induced by atmospheric N deposition can have serious consequences for forest health in many regions. In order to evaluate whether foliar may be a robust, regional-scale measure of the onset of N saturation in forest ecosystems, we assembled a large dataset on atmospheric N deposition, foliar and root and N concentration, soil C:N, mineralization and nitrification. The dataset included sites in northeastern North America, Colorado, Alaska, southern Chile and Europe. Local drivers of N cycling (net nitrification and mineralization, and forest floor and soil C:N) were more closely coupled with foliar than the regional driver of N deposition. Foliar increased non-linearly with nitrification:mineralization ratio and decreased with forest floor C:N. Foliar was more strongly related to nitrification rates than was foliar N concentration, but concentration was more strongly correlated with N deposition. Root was more tightly coupled to forest floor properties than was foliar . We observed a pattern of decreasing foliar values across the following species: American beech>yellow birch>sugar maple. Other factors that affected foliar included species composition and climate. Relationships between foliar and soil variables were stronger when analyzed on a species by species basis than when many species were lumped. European sites showed distinct patterns of lower foliar , due to the importance of ammonium deposition in this region. Our results suggest that examining values of foliage may improve understanding of how forests respond to the cascading effects of N deposition.     

Estimation of surface charges in some biological membranes

Summary The resting membrane potential data existing in the literature for the giant axon of the squid, frog muscle and barnacle muscle have been analyzed from the standpoint of the theory of membrane potential due to Kobatake and co-workers. The average values derived for the effective charge density (where is a constant, , and represents the fraction of counterions that are free, and is the stoichiometric charge density in the membrane) present on the different biomembranes existing in their normal ionic environment are 0.3, 0.325 and 0.17 M for the squid axon, frog and barnacle muscles, respectively. On the assumption that the values of are 0.4 and 0.2 for nerve and muscle membranes, respectively, values of 0.75, 1.62 and 0.85 M have been derived for the stoichiometric charge density present in the respective biological membranes. These correspond to 1 negative charge per 222, 103 and 195 Å of the membrane area of the squid axon, frog and barnacle muscles, respectively.