bluuebunny/crossref_metadata_2025 huggingface dataset:
CYANIDE SENSITIVITY OF RESPIRATION DURING AGEING OF ARUM SPADIX SLICES
Authors: WEDDING R. T. , MCCREADY C. C. , HARLEY J. L.
Published: May 2006

Summary

Slices of the sterile spadix of Arum may show variable responses ranging from inhibition to stimulation of respiration when exposed to cyanide. Some of the factors responsible for this variation in response were determined to be: (1) age of the spadix‐more mature spadices tend to be unaffected or stimulated by cyanide as opposed to very young spadices, which are inhibited; (2) thickness of the slice made from the spadix‐thin (c. 60 μm) slices are stimulated by 2.5 mM KCN while thick (>200 μm) slices are inhibited; (3) ageing of slices in aerated water‐this response is complex, with slices c. 100 μm thick freshly cut from spadices of intermediate maturity being stimulated by cyanide initially. During the following 24 hours, however, the respiration of the slices is inhibited by cyanide, but from 2–5 days after slicing the spadix slices reach a plateau of stimulation where rates may be almost doubled by cyanide. This is followed by a decline after 8 days' ageing to a situation in which respiration is unaffected by cyanide.

An inhibitor of cyanide‐resistant respiration, m‐chlorobenzhydroxamic acid, strongly inhibits spadix respiration, with a Kl similar to that of KCN. The effect of this inhibitor is additive to that of cyanide and in appropriate conditions, the two inhibitors together will completely inhibit Arum spadix respiration.
EFFECTS OF WATER STRESS ON GROWTH AND NITROGEN‐FIXING ACTIVITY OF TRIFOLIUM REPENS
Authors: ENGIN MUJGAN , SPRENT JANET I.
Published: May 2006

Summary

The growth and nitrogen fixation of Trifolium repens have been investigated during the imposition of and recovery from different levels of water stress. Growth (measured as fresh and dry weight of roots and shoots, shoot length and nitrogen content) and nitrogen fixation (per plant and per unit weight of nodule) were depressed by application of water stress. The ability of plants to recover and the time taken for recovery were both related to the duration of the stress period. Meristematic activity in nodules was resumed after watering, making clover nodules more resistant to stress than plants, such as soybean, with spherical nodules.

Nitrogen fixation, estimated by the acetylene reduction technique, was compared with the total nitrogen content of plants. Differences between the estimated and actual nitrogen content varied with age and degree of water stress.
SULPHUR DIOXIDE: ITS EFFECT ON PHOTO‐SYNTHETIC 14C FIXATION IN LICHENS AND SUGGESTED MECHANISMS OF PHYTOTOXICITY
Authors: PUCKETT K. J. , NIEBOER E. , FLORA W. P. , RICHARDSON D. H. S.
Published: May 2006

Summary

The toxicity to lichens of dissolved sulphur dioxide (as measured by net photosynthetic 14C fixation) was studied as a function of pH and is linked with the oxidation‐reduction properties of sulphur dioxide. An examination of pigments from lichens and spinach exposed to aqueous sulphur dioxide in vivo and in vitro suggests that the increased toxicity observed at low pH values is associated in part with the destruction of chlorophyll by an irreversible oxidation process.
INDUCTION OF NITRATE REDUCTASE IN LEAVES OF BARLEY IN THE DARK
Authors: ROTH‐BEJERANO NURITH , LIPS S. HERMAN
Published: May 2006

The induction of nitrate reductase activity in barley leaves normally requires light in addition to nitrate. However, nitrate reductase activity was induced in darkness in detached etiolated leaves when these were incubated with nitrate and glycollate. Other effective carbon compounds were sucrose, glucose or phosphoglyceric acid. Acetate, pyruvate or succinate was ineffective. Sodium bisulphite inhibited the stimulatory effect of glycollate or sucrose on enzyme induction. It is suggested that the induction of nitrate reductase requires the concomitant reduction of nitrate and that the NADH required for the reduction is derived from the metabolism of glycollate.
CARBOHYDRATE METABOLISM IN THE FUNGUS DENDRYPHIELLA SALINA IV. ACETATE ASSIMILATION
Authors: HOLLIGAN P. M. , JENNINGS D. H.
Published: May 2006

Both mannitol and arabitol are synthesized by Dendryphiella salina when acetate is supplied as the sole carbon source. As in media containing glucose, there is a rapid turnover of the hexitol. Addition of glucose to the medium inhibits acetate uptake and leads to marked increases in yields of residual dry weight of fungus and respiratory carbon dioxide.
THE EFFECT OF GIBBERELLIC ACID, KINETIN AND INDOLYLACETIC ACID ON THE LATERAL MOVEMENT OF LABELLED PLANT GROWTH REGULATORS IN WILLOW STEMS
Authors: FIELD R. J.
Published: May 2006

Using willow stem segments it has been possible to show that the presence of gibberellic acid in the xylem can influence the lateral mobility of radioactive indolylacetic acid and its principal metabolite, indoleacetylaspartic acid. The extent of the lateral movement of indolylacetic acid depends on the concentration of endogenous gibberellin in the xylem, and movement may be increased by exogenous gibberellin applications to the xylem. The mechanism controlling the lateral movement of 2, 4‐dichlorophenoxyacetic acid and 2, 4, 5‐trichlorophenoxyacetic acid appeared to be somewhat different and there was no positive movement towards gibberellin.

These results are discussed in relation to previous experimentation on the interaction of plant growth regulators during transport. It is suggested that gibberellins may influence cell membranes and this may account for their effects on the transport of indolylacetic acid.
ASPARAGINE ACCUMULATION IN GENETICALLY CHLOROTIC TISSUE
Authors: LAND J. B. , NORTON G.
Published: May 2006

Soluble amino acid analyses of the green and chlorotic areas of several variegated plants generally showed that amino acids accumulated in the chlorotic tissues. Asparagine levels were consistently and conspicuously higher in the chlorotic areas. This pattern is discussed in the context of other physiological chloroses.
PROSTELAR AUTOLYSIS: A FURTHER EXAMPLE OF A PROGRAMMED SENESCENCE
Authors: BERJAK PATRICIA , LAWTON JUNE R.
Published: May 2006

A pattern of degeneration, which terminates in total autolysis of the cells concerned, is described for certain stelar cells (termed prostelar cells) in young regions of the root in cress. The early senescence of these cells is characterized by extensive cytolysome formation, while final autolysis follows tonoplast dissolution. Degenerated prostelar cells are soon replaced by differentiating cambial derivatives.

It is suggested that the sequence of events which occurs during the degeneration of these cells is under genetic control and the possibility of genetic programmes controlling certain senescence processes in plants is considered. These observations are discussed in the light of generally held concepts of plant anatomy.
THE DISPERSAL EFFECTIVENESS OF THE ACHENE–PAPPUS UNITS OF SELECTED COMPOSITAE IN STEADY WINDS WITH CONVECTION
Authors: SHELDON J. C. , BURROWS F. M.
Published: May 2006

The role of the involucral bracts of the Compositae capitulum in fruit dispersal, the behaviour of the pappus of composite fruits to changes in humidity, and the presentation of the achene‐pappus units for wind dispersal, are briefly reviewed. Arguments put forward in the literature for and against the effectiveness of the pappus in facilitating wind dispersal are presented. A method is described for comparing the dispersal efficiency of achene‐pappus units of selected composites. The computed trajectories for fruits of selected species under the independent effects of wind speed and plant height, wind speed and boundary layer, and the combination of these with convection velocity are given.

It is shown that the efficiency of dispersal is determined more by the fine details of the pappus geometry, which directly affects its aerodynamic properties, than by the size ratio of pappus to achene. Under steady horizontal winds, increased height of fruit release increases dispersal distance. Reported patterns of wind dispersal are discussed in terms of air movement, flight path interference by neighbouring plants and, for some species, the fruit dissemination mechanism.

While increased wind velocities increase the trajectory distance, dispersal of many composites is hampered by the pappus response to humidity. Increased dispersal distances are given by steady convection currents, whereas turbulence may either curtail or prolong transportation.

The apparent inefficiency of wind dispersal reported under field conditions is explained by the combined effects of these various environmental factors upon the dispersal units during the period of dissemination.
A COMPARISON OF DEVELOPMENT OF PUCCINIA HORDEI OTTH. ON NORMAL AND SLOW RUSTING VARIETIES OF BARLEY (HORDEUM VULGARE L.) USING ANALYSES OF FUNGAL CHITIN AND MANNAN
Authors: WHIPPS J. M. , CLIFFORD B. C. , RODERICK H. W. , LEWIS D. H.
Published: May 2006

The growth and development of Puccinia hordei Otth. race F on leaves 3 and 5 of barley varieties Gold and Peruvian, normal and slow rusters respectively, were compared using histological and biochemical techniques. Assays of chitin and mannan contents agreed well with histological observations of infection and were linearly related to each other. The use of these and other compounds as indices of fungal growth is discussed.
NITRATE‐NITROGEN ASSIMILATION IN THE LEAVES OF HELIANTHUS ANNUUS L.
Authors: KAISER J. J. , LEWIS O. A. M.
Published: May 2006

Xylem sap analyses of 5‐week‐old plants of Helianthus annuus L. fed at high and low nitrate concentrations show that between 77 and 94 % of the nitrogen conveyed to the leaf by the xylem is in the form of nitrate, present at up to 300 % of its concentration in the feeding solution, thus confirming nitrate as the major nitrogen source of leaves of this species when its roots are nitrate fed. Organic nitrogen is mainly in the form of glutamine.

The pathways of nitrogen assimilation in the leaves of H. annuus following petiolar nitrate feeding at two concentrational levels have been investigated by an 15N infiltration technique in the presence of the glutamine synthetase inhibitor, methionine sulphoximine (MSO). In the absence of MSO and over a 30 min time‐course the main diversion of newly reduced nitrate was to glutamine with a secondary enrichment of glutamate. In the presence of MSO intracellular pools of all the amino compounds, with the exception of threonine, became conspicuously depleted, suggesting that conditions of nitrogen stress had been induced. There was an almost complete restriction of the supply of newly reduced 15N to amino acid assimilation with the resultant accumulation of large 15N ammonium pools. Glutamate dehydrogenase activity was unaffected by the MSO treatment.

These experimental results indicate the almost exclusive role of the glutamine synthetase‐ glutamate synthase pathway in the assimilation of newly reduced nitrate into amino acid metabolism in the leaves of H. annuus.
ENZYMES OF AMMONIA ASSIMILATION IN THE CYTOSOL OF DEVELOPING SOYBEAN ROOT NODULES
Authors: SEN DIPANKAR , SCHULMAN HERBERT M.
Published: May 2006

Glutamine synthetase, glutamate synthase and glutamate dehydrogenase activities were measured in the cytosol extracted from developing effective soybean root nodules and compared to the activities found in cytosol extracted from ineffective soybean root nodules and soybean root tissue. In the cytosol of effective soybean root nodules glutamine synthetase activity was found to increase up to floral initiation while glutamate dehydrogenase activity decreased. Glutamate synthase activity was detected but it did not increase as much as glutamine synthetase. In ineffective nodule cytosol and root tissue much lower levels of glutamine synthetase and similar levels of glutamate dehydrogenase, as compared to effective nodule cytosol, were found but no glutamate synthase was detectable. The results indicated that glutamine synthetase/glutamate synthase cycle is operative for ammonia assimilation in effective soybean root nodules and glutamate dehydrogenase probably has no synthetic role.
ULTRASTRUCTURAL ASPECTS OF HOST‐ENDOPHYTE RELATIONSHIPS IN ARBUTUS UNEDO L. MYCORRHIZAS
Authors: FUSCONI ANNA , BONFANTE‐FASOLO PAOLA
Published: May 2006

Summary

A morphological examination of white‐amber mycorrhizal roots of Arbutus unedo L. has been carried out using light and electron microscopy and naturally infected tissue. This type of mycorrhiza is slightly different from the typical arbutoid type; it is characterized by a few hyphae which extend along the surface of the root without forming a true mantle. They penetrate between the epidermal cells, giving rise to the Hartig net, and invade the epidermal cells. All the hyphae have simple septa and associated Woronin bodies characteristic of ascomycetous fungi. Intracellular hyphae are surrounded by invaginated host plasmalemma and by an inter‐facial material of varying thickness. No evidence of lysis or digestion of the intracellular hyphae by the plant cells has been observed, the fungal hyphae generally outliving the host epidermal cells.
PHOTOSYNTHETIC CAPACITY CHANGES IN PELTIGERA I. THE SYNTHESIS OF ADDITIONAL PHOTOSYNTHETIC UNITS IN P. PRAETEXTATA
Authors: KERSHAW K. A. , WEBBER M. R.
Published: May 2006

Summary

Changes in the photosynthetic capacity of Peltigera preaetextata (Somm.) Vain, over the course of a year have been examined using photosynthetic‐illumination curves. The results have been interpreted using the photosynthetic response models originally proposed by Prézelin. The low net photosynthetic rates obtained following prolonged winter snow cover are interpreted as resulting from the interruption of energy transduction in some photosynthetic units. In spring, full energy transduction is rapidly re‐established by the storage of experimental replicates at a warm temperature and results in a marked increase in net photosynthetic rates. As expansion of the tree canopy takes place both apparent quantum efficiency and photosynthetic capacity increase markedly, whilst respiration decreases significantly, providing high rates of net photosynthesis even under light levels as low as 75 μmol m−2 s−1. This change in summer capacity is interpreted as being due to the synthesis of additional photosynthetic units in response to the low light conditions on the woodland floor. The data are discussed both in relation to comparable events in other lichen species and to the potential significance of seasonal changes in photosynthetic capacity in the ecology of P. praetextata.
IRRADIANCE AND ADVENTITIOUS ROOT FORMATION IN STEM CUTTINGS OF PHASEOLUS AUREUS ROXB.
Authors: JARVIS B. C. , ALI A. H. N.
Published: May 2006

Summary

Rooting of cuttings of mung bean (Phaseolus aureus Roxb.) is enhanced when the stock plants, from which cuttings are taken, are grown under high irradiance. When rooting is induced by treatment with indolebutyric acid (IBA), high irradiance during the rooting period increases the number of roots developing on each cutting. However, when it occurs in the absence of supplied auxin, rooting is increased when cuttings are held under low irradiance. Irrespective of whether roots are induced by supplied IBA or by endogenous factors their growth, as evidenced by mean length, is greatest when stock plants are raised under high irradiance but cuttings are maintained under low irradiance.
THALLUS SIZE AS A COMPLICATING FACTOR IN THE PHYSIOLOGICAL ECOLOGY OF LICHENS
Authors: LARSON D. W.
Published: May 2006

Summary

The relationship between size of lichen thallus and net photosynthetic rate, respiration rate, rate of water uptake, rate of water loss and maximum thallus water content has been examined in five species of Umbilicaria. While two species show large effects of thallus size, three others show small, or no effects. The lack of a consistent pattern complicates the studies of physiological ecology in these and other lichen species because the vast majority of the published literature contains no mention of the dimensions of thallus or clones used. A major research effort should be made to determine other physiological functions that are age‐ or size‐dependent. In addition, future work should include, where possible, information regarding dimensions of the thallus used and the range of dimensions normally found in the field. Only in this way can conclusions be tested by other workers.
THE POISONING OF ROOTS OF ZEA MA YS BY NICKEL IONS, AND THE PROTECTION AFFORDED BY MAGNESIUM AND CALCIUM
Authors: ROBERTSON A. I.
Published: May 2006

Summary

The growth of seedlings oiZea mays L. has been studied in water cultures containing Ni2+, Mg2+ and Caa+ singly and in certain combinations. Root growth was reduced to half that of the controls (RG50) by as little as 01 mg I−1 Ni2+. This poisoning was prevented by 4 mg I”1 Mg2+ and by 32 mg T1 Ca2+. RG50 for Mg2+ alone was 64 mg T1 and for Ca2+ more than 1000 mg I−1. Root growth could be stopped within 8 h of exposure to 1 mg I−1 Ni2+. In the absence of Ni2+, Ca2+ protected against Mg2+ toxicity but Mg2+ did not reduce the effects when CaCl2 created osmotic loss at very high concentration. In combination, a ratio of 6:1 excess of Mg: Ca was necessary for Mg2+ to begin to reduce growth. At higher concentrations Mg2+ exerted its own toxicity despite the presence of Ca2+. When Ni2+ would otherwise have poisoned growth, Ca2+ added only to the relief of poisoning by Mg2+ if the Ca2+ was in excess by more than 4:1 over Mg2+. Thus Mg2+ appeared to be more fitted to prevent Ni2+ poisoning, yet at higher concentrations it was toxic itself, while Ca2+ could at still higher concentrations protect against both Ni2+ and Mg2+. Ni2+ poisoned growth by stiffening the expansion zone tissues and by destroying the integrity of root meristems. This latter was the first and most important toxic effect, and was achieved by arresting mitosis.
PHOTOCONTROL OF TURION FORMATION BY POTAMOGETON CRISPUS L. IN THE LABORATORY AND NATURAL WATER
Authors: CHAMBERS P. A. , SPENCE D. H. N. , WEEKS D. C.
Published: May 2006

Summary

The freshwater angiosperm Potamogeton crispus produces specialized vegetative buds, known as turions, in early summer, in contrast to their autumn production by other temperate climate species. Laboratory experiments showed that turion production by P. crispus is triggered by long days (16 h or longer) and high temperatures (16 °C and above) together. Long days represent a photoperiodic signal apparently perceived by phytochrome. A midnight exposure to dim R light is necessary to induce turion formation in plants kept under short days, irrespective of total daily light dose. A single long day suffices to initiate turion formation.

Under inductive long warm days few turions form at low photon fluence rates (whatever the total daily light dose) or at low R: FR ratios near 1 during the photoperiod. Rate and magnitude of turion production are greatly increased by increased photon fluence rates and R: F ratios above 1. Sucrose feeding hastens turion development, but turion initiation is not significantly altered.

As predicted from experimental findings and natural lakewater photoperiods and temperatures, turions were observed on plants in lakes studied from June until August. Also, turions were confined as predicted to approximately the upper 15 m depth range in lakes where R: FR ratios and photon fluence rates were inductively high. Below these depths the R: FR ratio remains high but photon fluence rate is inadequate. Thus laboratory and field findings concur. In north temperate waters, turions of P. crispus appear to act as summer propagules which settle and germinate by autumn, rather than as overwintering hibernaculae.
ION AND WATER TRANSPORT IN SEEDLINGS OF MUSTARD (SINAPIS ALBA L.)
Authors: COLLINS J. C. , ABBAS M. A.
Published: May 2006

Summary

Ion and water transport were measured in young mustard seedlings which had been grown in the dark on a simple culture medium. The growth of seedlings was exponential during the period 2 to 5 d from germination, though there was a decline in the rate of respiration with age. A comparison of the fluxes from excised roots with those in the roots of intact plants showed that the fluxes of potassium and chloride were much greater in intact plants, and it is argued that transport to the shoot might be regulated by some factors from the intact shoot. The flux of water was similar in both systems.
GERMINATION RESPONSES TO LIGHT AND ALTERNATING TEMPERATURES IN EUROPEAN POPULATIONS OF DACTYLIS GLOMERATA L.
Authors: PROBERT R. J. , SMITH R. D. , BIRCH P.
Published: May 2006

Summary

Germination responses to light and alternating temperatures were investigated in a range of populations of Dactylis glomerata L. of contrasting origin. Despite quantitative variation, similar responses to both factors were recorded in 12 British populations. In 11 European populations, levels of response were dependant on original dormancy status and apparently related to climatic origin. Whereas northern European populations required both light and alternating temperatures for maximum germination, Mediterranean populations germinated to high levels in complete darkness at a constant temperature. In Mediterranean populations, germination capacity declined sharply with increasing daily photoperiod in light from warm white fluorescent tubes. It is postulated that different patterns of response in European populations were related to differences in a basic mechanism of germination control involving phytochrome.
GERMINATION RESPONSES TO LIGHT AND ALTERNATING TEMPERATURES IN EUROPEAN POPULATIONS OF DACTYL1S GLOMERATA L.
Authors: PROBERT R. J. , SMITH R. D. , BIRCH P.
Published: May 2006

Summary

Basic patterns of germination response to light and alternating temperatures were relatively stable in three European populations of Dactylis glomerata L. during four years of cultivation in field plots. Small inconsistent quantitative differences were probably due to differences in the reproductive output of individual genotypes and seasonal variation in climatic factors. Germination responses were directly related to temperature conditions (over the range 6 to 26 °C) which prevailed during seed development and maturation. The relative effects of light and alternating temperatures were independent of maturation temperature suggesting a physiological link in the requirement for these factors.
CHLOROPHYLL A FLUORESCENCE AS A QUANTITATIVE PROBE OF PHOTOSYNTHESIS: EFFECTS OF CO2 CONCENTRATION DURING GAS TRANSIENTS ON CHLOROPHYLL FLUORESCENCE IN SPINACH LEAVES
Authors: FURBANK ROBERT T. , WALKER DAVID A.
Published: May 2006

The relationship between changes in chlorophyll a fluorescence and changes in CO2 concentration in spinach leaves is analyzed. The height of the fluorescence excursion, when plotted against the CO2 concentration during the transient, results in a hyperbola. When these data are replotted on an inverse‐reciprocal plot, an apparent Km (CO2) for the fluorescence transient can be obtained which closely approximates the Km (CO2) for carbon assimilation under similar conditions. Transitions in CO2 concentration at 2 % O2 result in deviation from this hyperbolic relationship, reducing the apparent Km (CO2) for this process. The relationship between carbon assimilation and chlorophyll fluorescence is discussed with reference to the two components of fluorescence quenching. This technique raises the possibility that chlorophyll fluorescence could be used as a quantitative as well as a qualitative tool in plant screening.
EFFECTS OF NITROGEN DEPRIVATION ON RATES OF UPTAKE OF NITROGENOUS COMPOUNDS BY THE DIATOM, PHAEODACTYLUM TRICORNUTUM BOHLIN
Authors: SYRETT P. J. , FLYNN K. J. , MOLLOY C. J. , DIXON G. K. , PEPLINSKA A. M. , CRESSWELL R. C.
Published: May 2006

Summary

A culture of Phaeodactylum tricornutum was suspended in nitrogen‐free growth medium under conditions which favoured photosynthesis. Nitrogen deprivation was continued for 60 h and, over this period, samples were removed for measurement of rates of uptake of arginine, guanine, nitrate, nitrite, lysine, methylammonium and urea. In another experiment, the effect of nitrogen deprivation on the ability to take up methylammonium and ammonium was compared. Cells developed, or increased, their abilities to take up all of these nitrogen compounds during nitrogen deprivation but ability to take up the two amino acids increased only slowly whereas the ability to take up the other compounds increased markedly during the first few hours of deprivation. The maximum rates of uptake developed were some 50–100 × higher for methylammonium and ammonium than they were for the other compounds. The rates of uptake are compared with those necessary to sustain growth.
REGULATION BY AZIDE OF HETEROCYST AND NITROGENASE IN AZIDE‐RESISTANT MUTANTS OF THE CYANOBACTERIUM, NOSTOC MUSCORUM
Authors: BAGCHI S. N. , SINGH D. T. , SINGH H. N.
Published: May 2006

Summary

A novel class of azide‐resistant mutants of N, muscorum is described in which azide caused inhibition of heterocyst differentiation and nitrogen fixation without causing inhibition of growth. The results indicate the utilization of azide, as a fixed nitrogen source, by the mutant strain. An increase in the ability to take up azide and in the phycocyanin/chlorophyll ratio following growth of the mutant in azide‐containing medium are additional findings which support the conclusion that the mutant utilizes azide as a source of nitrogen. In the parental strain, Ca2+‐dependent and Mg2+‐dependent ATPases, and cellular nitrate reductase were inhibited by azide. The corresponding ATPases from the mutant strain were not inhibited by azide. There was evidence, in cell‐free extracts, for an enzyme system which utilized azide as an electron acceptor and NADPH‐ferredoxin as electron donor. The activity of this system was significantly higher (on a protein basis) in cells of the mutant grown on azide than in cells of either the parent or the mutant when grown on nitrate.

It is suggested that the azide resistance of this class of mutant is due to a mutation which leads to azide resistant Ca2+‐ and Mg2+‐ ATPases. Such a mutation may allow an azide utilizing system, inherently present in both parent and mutant strains, to be expressed.
COMPARATIVE STUDIES ON THE SUB‐UNIT COMPOSITION OF THE ALBUMINS, VICILINS AND LEGUMINS OF ISOLATED PROTEIN BODIES FROM COTYLEDONS OF DRY SEEDS OF TWO MEMBERS OF THE LEGUMINOSAE: CYTISUS SCOPARIUS (L.) LINK AND C. SCOPARIUS SSP. MARITIMUS (ROUY) HEYWOOD
Authors: CITHAREL J. , CITHAREL L.
Published: May 2006

Summary

The isolated protein bodies of Cytisus scoparius (L.) Link and Cytisus scoparius ssp. maritimus (Rouy) Heywood were observed by scanning electron microscopy; they showed comparable shapes and sizes. The protein content and the sub‐unit composition of the fractionated albumins, vicilins and legumins, however, showed significant electrophoretic differences between the two plants, both at the qualitative and quantitative levels.
ASSIMILATION OF 15NH4+BY BEECH (FAGUS SYLVATICA L.) ECTOMYCORRHIZAS
Authors: MARTIN F. , STEWART G. R. , GENETET I. , LE TACON F.
Published: May 2006

Summary

Ammonia assimilation has been followed in ectomycorrhizal roots of Fagus sylvatica. The absorption of ammonium ions was associated with a rapid synthesis of free amino acids in mycorrhizal tissues, glutamine being the most prominent. In the presence of [15N]ammonium, glutamate, glutamine and alanine became the most strongly labelled metabolites of ectomycor‐rhizas. Nitrogen‐15 nuclear magnetic resonance spectroscopy demonstrated that the glutamine amide‐N was the most highly enriched component of the extracts. Methionine sulphoximine and albizine, inhibitors of glutamine synthetase and glutamate synthase, almost completely blocked the incorporation of 15N label into amino acids and induced an accumulation of NH4+. These observations suggest that in the ammonia‐fed beech ectomycorrhizas, ammonia assimilation occurs mainly via the glutamine synthetase/glutamate synthase pathway, and that glutamate dehydrogenase plays little, if any, part in this process. Alternative models for the nitrogen assimilation pathways in fungal and host tissues are presented.
GERMINATION RESPONSES TO LIGHT AND ALTERNATING TEMPERATURES IN EUROPEAN POPULATIONS OF DACTYLIS GLOMERATA L.
Authors: PROBERT R. J. , SMITH R. D. , BIRCH P.
Published: May 2006

Summary

Detailed germination responses to temperature and light in two populations of Dactylis glomerata L. originating from S.E. Denmark and W. France were defined using thermogradient bars. Despite quantitative differences patterns of response were broadly similar. In both cases seeds were sensitive to the relative periods spent at the warm and cool phases of alternating temperature cycles with germination markedly reduced in diurnal cycles involving a 16 h warm phase and an 8 h cool phase. Whereas the proportion of seeds capable of germination increased sharply as the amplitude of temperature alternation increased the optimum amplitude was dependent on both the period spent at each phase and the presence or absence of light. Even under optimum temperature conditions there was an overriding requirement for light in a high proportion of individuals. When five 21/11 °C cycles of reduced duration were applied at 24 h intervals, 1 h/2 h alternations were as effective in stimulating germination as diurnal cycles. Germination response was directly related to the logarithm of the number of diurnal 21/11 °C cycles applied in three different seed samples. Sensitivity was not related to inherent dormancy status (between populations) or to a degree of after‐ripening.
IDENTIFICATION OF VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI IN ROOTS OF LEEK (ALLIUM PORRUM L.) AND MAIZE (ZEA MAYS L.) ON THE BASIS OF ENZYME MOBILITY DURING POLYACRYLAMIDE GEL ELECTROPHORESIS
Authors: HEPPER CHRISTINE M. , SEN R. , MASKALL C. S.
Published: May 2006

Summary

The mobilities of three enzymes, esterase (EST), glutamate oxaloacetate transaminase (GOT) and peptidase (PEP), during polyacrylamide gel electrophoresis have been used to identify individual species of vesicular–arbuscular mycorrhizal fungi in roots. The enzyme banding patterns obtained from mycorrhizal root extracts were compared with those of uninfected roots. Chlamydospores, external mycelium and internal mycelium (obtained by enzymic digestion of host root tissue) were used as controls to confirm the position of the fungal specific enzyme bands on the gels. Glomus caledonium (Nicol. and Gerd.) Trappe and Gerd. and Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe could be detected in leek (Allium porrum L.) roots against the host background by the mobility of bands of EST, GOT and PEP activity and it was possible to detect both G. caledonium and G. mosseae in leek roots which had been grown in the presence of a mixed inoculum, by staining for any of these three enzymes. Glomus mosseae could be identified in maize (Zea mays L.) roots by location of GOT and PEP activity but the major bands of EST, GOT and PEP activity in G. caledonium had the same mobility as those of maize and so this fungus could not be easily identified in this host using these experimental conditions. Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe type E3 had a characteristic PEP band which was separable from leek and maize host bands and this fungus could also be identified in maize roots by the position on the gel of fungal GOT activity.
The Location of Culture: The Urban Culturalist Perspective
Authors: Borer Michael Ian
Published: May 2006

The majority of research in urban sociology tends to favor the study of urbanization, the development and growth of cities, over urbanism, the way of life in cities. Here, I identify a strand of urban sociology that explicitly focuses on the latter and introduce a theoretical framework for investigating culturally significant urban places. The urban culturalist perspective consists of six domains of research:1) images and representations of the city; 2) urban community and civic culture; 3) place‐based myths, narratives, and collective memories; 4) sentiment and meaning of and for places; 5) urban identities and lifestyles; and 6) interaction places and practices. These distinct but related domains collectively provide a framework for addressing culture‐place relationships in cities by offering a clear window into the ways that pepole use places as part of their cultural repertoires and how those repertoires can affect a city's social and physical environment.
Clinical Experience with Tiered Atrial Therapies and Atrial Arrhythmia Prevention Algorithms in a Dual Chamber Cardioverter Defibrillator
Authors: DAOUD EMILE G. , NADEMANEE KOONLAWEE , FUENZALIDA CHARLES , TOMASSONI GERY F. , SCHUGER CLAUDIO , CHISNER MICHAEL , SIMONES MELISSA , SCHWARTZ MARK , REEVE HELEN
Published: May 2006

Introduction: The acceptance of atrial arrhythmia features in implantable cardioverter defibrillators (ICDs) will depend on their ability to appropriately discriminate atrial tachyarrhythmias/atrial fibrillation (AT/AF). This study tested the effectiveness of an atrial/ventricular ICD with advanced atrial detection and new algorithms designed to prevent atrial arrhythmias.

Methods and Results: Ninety‐five patients were implanted with a dual chamber ICD (Model 1900, Guidant Corporation, MN, USA) at 25 US centers. Ten patients received a coronary sinus (CS) lead allowing a defibrillation vector for AT/AF cardioversion. Follow‐up was 12.2 months. The addition of new atrial features designed for detection, discrimination, and prevention of AT/AF had no adverse effect upon detection of induced ventricular fibrillation (VF) (mean detection time with new features ON was 2.22 seconds vs 2.19 seconds with features OFF). A total of 100% of the induced and spontaneous ventricular and atrial arrhythmias receiving shock therapy were reviewed as appropriate detection. Atrial shock conversion efficacy for spontaneous and induced AT/AF episodes was 83% and 96%, respectively (144 spontaneous, 162 induced episodes). A 3‐month randomized crossover trial of atrial preventative pacing features did not result in adverse effects, but there was no clinical efficacy for prevention of AT/AF.

Conclusion: Enhanced atrial detection and discrimination features combined with tiered atrial therapies did not adversely impact the ability of the ICD (Model 1900) to appropriately detect and treat ventricular tachyarrhythmias.
Atrial Thrombi—A Prospective Follow‐up Study over 3 Years with Transesophageal Echocardiography and Cranial Magnetic Resonance Imaging
Authors: Bernhardt Peter , Schmidt Harald , Hammerstingl Christoph , Lüderitz Berndt , Omran Heyder
Published: May 2006

Background: Patients with atrial fibrillation (AF) and atrial thrombi have an increased risk for cerebral embolism. However, there is little knowledge about the long‐term fate of atrial thrombi and the incidence of cerebral embolism in patients under oral anticoagulation. Methods: Consecutive patients with persistent or permanent AF and left atrial (LA) thrombi were included in the study. We performed serial and prospective transesophageal echocardiography, cranial magnetic resonance imaging, and clinical examinations during a period of 3 years. Oral anticoagulation was continued or initiated in all patients. A target INR of 2.5 was intended in all patients. Results: Forty‐three patients with LA thrombi and persistent or permanent AF were included. During the follow‐up period 31(72%) of the thrombi disappeared. Patients with disappearance of thrombi had significantly smaller thrombi (P < 0.01), a lower echogenicity of thrombi (P < 0.01), and a lower LA volume (P = 0.02). Twenty‐two (51%) patients suffered from cerebral embolism and/or death during the observation period. Five patients died due to embolic events. The only independent predictors of cerebral embolism were an elevated peak emptying velocity of the LA appendage (P < 0.001) and a history of previous thromboembolism (P < 0.01). Conclusions: Patients with persistent or permanent AF and atrial thrombi have a high long‐term risk of cerebral embolism and/or death (51%) even despite the oral anticoagulation therapy. Thrombus size may predict thrombus resolution under continued anticoagulation.
New insights into the molecular biology and targeted therapy of cutaneous T‐cell lymphomas
Authors: Klemke Claus‐Detlev , Goerdt Sergij , Schrama David , Becker Jürgen C.
Published: May 2006

Cutaneous T‐cell lymphoma is an extra‐nodal non‐Hodgkin lymphoma of mature T cells.These tumor cells home to and persist in the skin,producing a broad spectrum of clinical entities. Recent results of basic research on tumor biology and tumor immunology as well as molecular genetics of cutaneous T‐cell lymphoma have fostered the development of new therapeutic approaches. Several clinical trials testing these targeted therapies have shown encouraging results. This article provides an overview of recent research developments and therapeutic strategies for cutaneous T‐cell lymphoma.
Atg8L/Apg8L is the fourth mammalian modifier of mammalian Atg8 conjugation mediated by human Atg4B, Atg7 and Atg3
Authors: Tanida Isei , Sou Yu‐shin , Minematsu‐Ikeguchi Naoko , Ueno Takashi , Kominami Eiki
Published: May 2006

Murine Atg8L/Apg8L has significant homology with the other known mammalian Atg8 homologs, LC3, GABARAP and GATE‐16. However, it is unclear whether murine Atg8L modification is mediated by human Atg4B, Atg7 and Atg3. Expression of Atg8L in HEK293 cells led to cleavage of its C‐terminus. In vitro, the C‐terminus of Atg8L was cleaved by human Atg4B, but not human Atg4A or Atg4C. Atg8L‐I formed an E1‐substrate intermediate with Atg7C572S, and an E2‐substrate intermediate with Atg3C264S. A modified form of Atg8L was detected in the pelletable fraction in the presence of lysosomal protease inhibitors under nutrient‐rich conditions. Cyan fluorescent protein (CFP)–Atg8L colocalized with yellow fluorescent protein (YFP)–LC3 in HeLa cells in the presence of the inhibitors. However, little accumulation of the modified form of Atg8L was observed under conditions of starvation. These results indicate that Atg8L is the fourth modifier of mammalian Atg8 conjugation.
Association of parental smoking behaviors and absences in school‐age children: Implications for the nurse practitioner
Authors: Birney Margaret Hamilton , Hardie Thomas L. , Crowley Evelyn M.
Published: May 2006

Purpose:To examine the association between reported absences and parental smoking in school‐age children, aged 6–17, and to specifically explore the impact of maternal smoking on the health and attendance of school‐age children.

Data sources:The sample of 7488 parent–child dyads was randomly selected from the 2002 National Health Interview Survey, a multipurpose cross‐sectional household interview survey conducted by the Centers for Disease Control and Prevention. The parent sample included 2673 men and 4375 women. Children’s ages ranged from 6 to 17 with a mean of 11.7 years.

Conclusions:Maternal, but not paternal, present and past smoking behavior significantly impacts the child’s wellness and school attendance. The reasons for this disparity are unclear but may relate to synergistic effects of pre‐ and postnatal nicotine exposure, the traditional role of mother as caregiver, or specific smoking habits that increase environmental tobacco exposure.

Implications for practice:Assessment and educational strategies for families regarding the hazards of childhood exposure to environmental tobacco smoke are indicated. Specific implications for the role of the nurse practitioner across diverse specialties are addressed with emphasis on the need for development of gender, age, and culturally sensitive smoking cessation programs and support networks.
Synergistic Effects in Mixed
Escherichia coli
Biofilms: Conjugative Plasmid Transfer Drives Biofilm Expansion
Authors: Reisner Andreas , Höller Brigitte M. , Molin Søren , Zechner Ellen L.
Published: May 2006

Bacterial biofilms, often composed of multiple species and genetically distinct strains, develop under complex influences of cell-cell interactions. Although detailed knowledge about the mechanisms underlying formation of single-species laboratory biofilms has emerged, little is known about the pathways governing development of more complex heterogeneous communities. In this study, we established a laboratory model where biofilm-stimulating effects due to interactions between genetically diverse strains of
Escherichia coli
were monitored. Synergistic induction of biofilm formation resulting from the cocultivation of 403 undomesticated
E. coli
strains with a characterized
E. coli
K-12 strain was detected at a significant frequency. The survey suggests that different mechanisms underlie the observed stimulation, yet synergistic development of biofilm within the subset of
E. coli
isolates (
n
= 56) exhibiting the strongest effects was most often linked to conjugative transmission of natural plasmids carried by the
E. coli
isolates (70%). Thus, the capacity of an isolate to promote the biofilm through cocultivation was (i) transferable to the K-12 strain, (ii) was linked with the acquisition of conjugation genes present initially in the isolate, and (iii) was inhibited through the presence in the cocultured K-12 strain of a related conjugative plasmid, presumably due to surface exclusion functions. Synergistic effects of cocultivation of pairs of natural isolates were also observed, demonstrating that biofilm promotion in this system is not dependent on the laboratory strain and that the described model system could provide relevant insights on mechanisms of biofilm development in natural
E. coli
populations.
Flavonoid-Inducible Modifications to Rhamnan O Antigens Are Necessary for
Rhizobium
sp. Strain NGR234-Legume Symbioses
Authors: Broughton W. J. , Hanin M. , Relić B. , Kopciñska J. , Golinowski W. , Şimşek Ş. , Ojanen-Reuhs T. , Reuhs B. , Marie C. , Kobayashi H. , Bordogna B. , Le Quéré A. , Jabbouri S. , Fellay R. , Perret X. , Deakin W. J.
Published: May 2006

Rhizobium
sp. strain NGR234 produces a flavonoid-inducible rhamnose-rich lipopolysaccharide (LPS) that is important for the nodulation of legumes. Many of the genes encoding the rhamnan part of the molecule lie between 87° and 110° of pNGR234
a
, the symbiotic plasmid of NGR234. Computational methods suggest that 5 of the 12 open reading frames (ORFs) within this arc are involved in synthesis (and subsequent polymerization) of
l
-rhamnose. Two others probably play roles in the transport of carbohydrates. To evaluate the function of these ORFs, we mutated a number of them and tested the ability of the mutants to nodulate a variety of legumes. At the same time, changes in the production of surface polysaccharides (particularly the rhamnan O antigen) were examined. Deletion of
rmlB
to
wbgA
and mutation in
fixF
abolished rhamnan synthesis. Mutation of y4gM (a member of the ATP-binding cassette transporter family) did not abolish production of the rhamnose-rich LPS but, unexpectedly, the mutant displayed a symbiotic phenotype very similar to that of strains unable to produce the rhamnan O antigen (NGRΔ
rmlB-wbgA
and NGRΩ
fixF
). At least two flavonoid-inducible regulatory pathways are involved in synthesis of the rhamnan O antigen. Mutation of either pathway reduces rhamnan production. Coordination of rhamnan synthesis with rhizobial release from infection threads is thus part of the symbiotic interaction.
ELECTROCRYSTALLIZATION: I. SURFACE DIFFUSION
Authors: Rangarajan S. K.
Published: May 2006

A solution of the boundary value problem posed by Fleischmann and Thirsk is presented here for a generalized time dependence of η(t), the overpotential. The results for various techniques have been derived. Expressions for the transients have also been obtained. The formulations reported earlier for the potentiostatic, the faradaic impedance, and the galvanostatic techniques are deduced as special cases. It has also been shown that in the 'potential step method' a relatively simple relationship exists between the first and the second over-potentials.
A COMPARISON OF THE RAMAN CRYSTAL AND SOLUTION SPECTRA OF THE HEXANIOBATE AND HEXATANTALATE IONS
Authors: Tobias R. Stuart
Published: May 2006

not available
THE ACIDITY OF SOME SUBSTITUTED ACETONITRILES
Authors: Stewart Ross , O'donnell J. P. , Bowden Keith
Published: May 2006

not available
MAGNETIC STUDIES ON COPPER(II) TRIFLUOROACETATE
Authors: Thompson R. C. , Yawney D. B. W.
Published: May 2006

not available
STRUCTURAL DETERMINATIONS BY NUCLEAR MAGNETIC RESONANCE. 3-SUBSTITUTED PROPIONYL CHLORIDES
Authors: Schmid George H. , Weiler Larry S. J.
Published: May 2006

not available
CARBONYL AND THIOCARBONYL COMPOUNDS. IX. SYNTHESIS OF BENZOXANTHENE ETHERS BY THE ACTION OF TETRAHALO-o-BENZOQUINONES
Authors: Latif N. , Fathy I.
Published: May 2006

not available
REACTIVITY AND GEOMETRY IN ALLYLIC SYSTEMS: III. PHOTOSENSITIZED OXYGENATION OF CHOLEST-4-ENE, A STEROID OLEFIN WITH A CONFORMATIONALLY FLEXIBLE RING
Authors: Nickon A. , Mendelson W. L.
Published: May 2006

Photosensitized oxygenation of cholest-4-ene with hematoporphyrin in pyridine followed by reduction of the derived hydroperoxides gave five allylic alcohols in these relative amounts: cholest-4-en-3α-ol (Va, 37%); cholest-4-en-3β-ol (IVa, 7.5%); 5α-cholest-3-en-5-ol (VIIIa, 29%); 5β-cholest-3-en-5-ol (VIa, 2%); and cholest-5-en-4β-cl (Xa, 8.5%). A by-product from breakdown of the hydroperoxides was cholest-4-en-3-one (III, 6.5%). The Δ4-stenols are not primary products from the photosensitized process but arose by gradual isomerization of the initially derived 5-hydroperoxycholest-3-enes. When the original hydroperoxide mixture was allowed to stand in chloroform, the rearrangement went to completion and no isolable amounts of the Δ3-stenols remained. After rearrangement, Va and IVa were present in a ratio of about 8:1, and this sequence affords a convenient new route to cholest-4-en-3α-ol. The photooxidation products and their relative proportions are readily understood if oxygen can attack both half-chair conformations of ring A in cholest-4-ene and can cyclically abstract a quasi-axial (or an axial) allylic hydrogen. Conclusions are drawn on the importance of steric hindrance and of ring inversion on the photosensitized oxygenation reaction.
SYNTHESIS OF DERIVATIVES OF 1,2-DICHLORO-4-BENZENESULFONAMIDO-5-NITROBENZENE AND THEIR USE IN THE CHEMOTHERAPY OF SPONTANEOUS CANCERS
Authors: Woolley D. W. , Hoeven T. Van Der
Published: May 2006

A series of compounds related to 1,2-dichloro-4-benzenesulfonamido-5-nitrobenzene has been synthesized. These included derivatives in which ionizable groups had been placed in the para position of the benzenesulfonamido portion to confer on the compounds water solubility at physiological pH. Thus, carboxyl and quaternary ammonium groupings were introduced in this position. Water solubility was also conferred by introduction at the same position of non-ionizable groups such as polyhydroxyalkylamido groups. Additional relatives of the parent compound in which the chlorine atoms were replaced by methyl groups, and in which para-substituted benzenesulfonamido groups replaced those in the 4 and 5 positions, were synthesized. These compounds were tested for their ability to cure permanently the spontaneous mammary cancers of two strains of mice. All compounds were tested in combination with 1,2-dimethyl-4-(p-carboxyphenylazo)-5-hydroxybenzene. The most active substance found was 1,2-dichloro-4-(p-carboxybenzenesulfonamido)-5-nitrobenzene.