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  • Hydroxyapatite  (5)
  • Anabaena  (3)
  • Anastrepha ludens  (3)
  • Springer  (11)
  • AGU (American Geophysical Union)
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  • Springer  (11)
  • AGU (American Geophysical Union)
Years
  • 1
    Electronic Resource
    Electronic Resource
    Mating behavior and male mating success in wildAnastrepha Ludens (Diptera: Tephritidae) on a field-caged host tree (1991)
    Springer
    Journal of insect behavior 4 (1991), S. 471-487 
    Details
    ISSN: 1572-8889
    Keywords: mating behavior ; courtship ; lek ; mating system ; Mexican fruit fly ; Anastrepha ludens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mating behavior and factors affecting mating success of males were studied using wild Anastrepha ludens on a fieldcaged host tree. The most common courtship sequence had five components: (1) male calls from the underside of a leaf, (2) female arrives to the maleoccupied leaf, (3) male orients to female and stops calling, (4) one or both approach to a face-to-face position 1–3 cm apart, and (5) male mounts female after 1–2 s. Courtship behavior was almost identical to that of laboratoryculture flies observed previously under laboratory conditions. Most malefemale encounters occurred at a height of 1–2m, well inside the outer canopy of the tree. Differential mating success by males occurred. No male mated more than once per day, owing possibly to a very short sexual activity period. Factors favoring mating success of males were survival ability and tendency to join male aggregations and to fight other males. Thorax length and age (9–11 days difference) had no effects on male copulatory success. Overall win/loss percentage was not related to mating success because the males that were most successful at mating fought mostly among themselves, driving their win/loss percentage down. However, these successful males (at mating) won most of their fights against less successful males. Results confirmed a lek mating system: males aggregated, called, and defended territories; territories did not contain femalerequired resources; and females exercised mate choice, apparently through selection of sites within leks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049332
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetics of hydroxyapatite dissolution in acetic, lactic, and phosphoric acid solutions (1992)
    Springer
    Calcified tissue international 50 (1992), S. 137-143 
    Details
    ISSN: 1432-0827
    Keywords: Hydroxyapatite ; Enamel ; Dissolution ; Kinetics ; Caries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The present study was undertaken in an attempt to relate the kinetics of hydroxyapatite dissolution to solution parameters, under experimental conditions relevant to the dental caries process. Thus, the dissolution of hydroxyapatite was studied in acetic, lactic, and dilute phosphoric acid solutions having initial pH values from 4 to 6. Rates of dissolution and the corresponding degree of saturation with respect to hydroxyapatite were determined at various times throughout the dissolution process. Rates of dissolution of all solutions were found to decrease with increasing degree of solution saturation and were greater in solutions with lower initial values of pH. However, rates of dissolution in partially saturated phosphoric acid solutions (without added organic acid) were at least one order of magnitude lower than those observed in the organic acid buffers with the same initial pH, over the same range of saturation values. The data obtained are consistent with a surface-controlled dissolution model in which the rate of dissolution is dependent upon the degree of saturation and the sum of the activities of the acidic species in solution, i.e., phosphoric and organic acids. These results suggest that in order to assess the cariogenic potential of a given medium (e.g., plaque fluid), one must determine both the degree of saturation with respect to the dissolving mineral and the activities of acidic species in solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298791
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  • 3
    Electronic Resource
    Electronic Resource
    Precipitation of hydroxyapatite from dilute solutions upon seeding (1977)
    Springer
    Calcified tissue international 24 (1977), S. 47-57 
    Details
    ISSN: 1432-0827
    Keywords: Calcification ; Crystal growth ; Hydroxyapatite ; Kinetics ; Precipitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The kinetics of precipitation of hydroxyapatite, HA, was studied by seeding dilute supersaturated solutions with well characterized HA crystals. In solutions having initial degrees of supersaturation comparable to those present in human serum, the precipitation rates were related to the thermodynamic driving force (degree of supersaturation with respect to HA) and not to the solution composition. The following relationshipR 0=KA(DS) n , whereR 0=initial precipitation rate, A=amount of seeds, DS=degree of supersaturation, and K andn are parameters obtained from the experimental data, was found to apply over a DS range of 6.6×1010 to 3.3×106. These observations are consistent with the occurrence of a simple growth process on the HA seeds. No evidence for the formation of discrete calcium phosphates other than HA was detected. The Ca/P molar ratio of the precipitating phase, calculated from solution compositions, was invariably higher than that expected for HA; this result is shown to be consistent with an initial adsorption phenomenon. Anomalous kinetic behavior was observed at low seeding levels and may relate to the surface phenomenon described. It is concluded that, most probably, under physiological conditions, formation and remineralization of hard tissues occur through the reported crystal growth process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02223296
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of human salivary proteins on the precipitation kinetics of calcium phosphate (1979)
    Springer
    Calcified tissue international 28 (1979), S. 7-16 
    Details
    ISSN: 1432-0827
    Keywords: Salivary proteins ; Adsorption ; Hydroxyapatite ; Precipitation inhibitors ; Crystal growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Inhibition of calcium phosphate precipitation in saliva, and prevention of the formation of mineral accretions on tooth surfaces, has been ascribed to the existence of inhibiting salivary macromolecules. Marked reductions in the crystal growth rate of hydroxyapatite (HA) seeds were measured in supersaturated solutions containing either of two proline-rich proteins, PRP1 or PRP3, or statherin; the three macromolecules were isolated from human parotid saliva. The reductions were also observed when the HA seeds were pretreated with solutions of the macromolecules before adding them to the supersaturated calcium phosphate solution. This effect was very similar in the case of the two PRPs and it was directly related to the extent of adsorption site coverage of these proteins on the HA seeds. The effect of statherin was larger than anticipated from its adsorption behavior. However, comparison on the basis of number of moles adsorbed per unit area of HA shows that the PRP are more effective inhibitors than statherin. The macromolecule concentrations used were considerably lower than those in the salivery secretions, therefore these macromolecules could readily prevent mineral accretion on tooth surfaces through their adsorption onto the enamel surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441212
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  • 5
    Electronic Resource
    Electronic Resource
    Inhibition of apatite crystal growth by the amino-terminal segment of human salivary acidic proline-rich proteins (1984)
    Springer
    Calcified tissue international 36 (1984), S. 651-658 
    Details
    ISSN: 1432-0827
    Keywords: Salivary proteins ; Hydroxyapatite ; Adsorption ; Precipitation-inhibitor ; Phosphoserine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Inhibition of seeded apatitic crystal growth by human salivary acidic proline-rich phosphoproteins (PRP) has been related to their adsorption onto the apatite seeds. The amino-terminal 30-residue segment of the PRP makes an important contribution to this adsorption. This peptide (PRP1(T1)) and its dephosphorylated analogue from PRP3 (PRP3(T1)DP) were prepared. They have identical sequences, except the phosphates at residues 8 and 22 in PRP1(T1) are absent from PRP3(T1)DP. Adsorption of these peptides onto hydroxyapatite and their effect on crystal growth from a defined supersaturated solution was studied. Adsorption behavior was adequately described by the Langmuir adsorption isotherm. The adsorption affinity constant of PRP1(T1) (K=20,200 ml/µmol) was more than 10 times the corresponding value for PRP3(T1)DP (1,800 ml/µmol), and similar to that of the parent protein, PRP1 (26,200 ml/µmol). Inhibition of crystal growth by the peptides was interpreted in terms of the fractional coverage of the maximum number of adsorption sites (as derived from the adsorption isotherms), suggesting that the molecules block, by adsorption, specific growth sites on these surfaces. Comparison of precipitation kinetics showed that PRP1(T1) is a more effective inhibitor than PRP3(T1)DP at the same initial concentration (10−6−10−7 M). However, on the basis of per mol adsorbed, PRP3(T1)DP displays a greater inhibitory activity; such a behavior is consistent with a more open molecular structure which blocks more growth sites per mol adsorbed than PRP1(T1). Because of its high affinity constant, preadsorbed PRP1(T1) remains in the condensed state in the supersaturated solution used, whereas the preadsorbed PRP3(T1)DP molecules desorb to some extent, resulting in a decrease in inhibitory activity. The results show that the amino-terminal segment of the PRP and the two phosphoserine residues present in this segment are particularly important in the function proposed for these proteins in the oral environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405385
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  • 6
    Electronic Resource
    Electronic Resource
    Adsorption of molecules of biological interest onto hydroxyapatite (1984)
    Springer
    Calcified tissue international 36 (1984), S. 48-59 
    Details
    ISSN: 1432-0827
    Keywords: Salivary proteins ; Adsorption ; Thermodynamics ; Kinetics ; Hydroxyapatite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Equilibrium and kinetic experiments were conducted to investigate the factors determining the adsorption of salivary macromolecules onto hydroxyapatite. Using amino acids and other small adsorbates, it was determined that the carboxyl attached to the α carbon does not appear to adsorb onto HA and the affinities of side-chain carboxyls are much smaller than that of the phosphate group (phosphoserine). Hydroxyl (serine) displays an extremely high affinity, but its adsorption site on HA is different and the number of such sites is much smaller than found for the rest of the functional groups investigated. It is shown that the information obtained from small molecules cannot be readily applied to prediction of the adsorption behavior of salivary macromolecules and polypeptides. The kinetics of adsorption of the salivary phosphopeptide statherin, a polyaspartate, and the salivary prolinerich phosphoprotein PRP3 are consistent with the reversibility of the adsorption process; no conclusion was possible in the case of the protein PRP1. Apparent irreversibility cannot be explained on the basis of multipoint binding or the properties of the carboxyl versus phosphate group; it appears that secondary structure determines to a significant extent the adsorption properties of the macromolecules. Calculation of the thermodynamic molar quantities of adsorption of PRP1, PRP3, andl-ASP onto HA showed that the process is entropically driven. The functional relationship between partial molar entropy and adsorption coverage is similar for the two proteins, but quite different from that for aspartate. Explanations for these results are advanced on the bases of changes in structure configurations and displacement of water from the adsorbate and the adsorbent surface, the second factor being the dominant one in the adsorption of a small molecule such asl-ASP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405293
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of iron deficiency on ferredoxin levels in Anabaena variabilis PCC 6309 (1990)
    Springer
    Archives of microbiology 153 (1990), S. 528-530 
    Details
    ISSN: 1432-072X
    Keywords: Anabaena ; Ferredoxin ; Flavodoxin ; Iron deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cultures of the nitrogen-fixing cyanobacterium Anabaena variabilis PCC 6309 were grown under several iron concentrations, and changes in growth rates and chlorophyll and phycocyanin concentrations were determined. The total amount of ferredoxin present in the cells was found to be dependent on the concentration of iron in the media, as was the pattern distribution of the two different forms of the iron-sulfur protein described in this organism. Flavodoxin was not found to be present in these cells even when they were grown in the absence of added iron, indicating that this flavoprotein does not replace ferredoxin in this particular strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00245260
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  • 8
    Electronic Resource
    Electronic Resource
    Flavodoxin from the nitrogen-fixing cyanobacterium Anabaena PCC 7119 (1988)
    Springer
    Archives of microbiology 150 (1988), S. 160-164 
    Details
    ISSN: 1432-072X
    Keywords: Anabaena ; Biochemical properties ; Flavodoxin ; Nitrogenase ; Photosystem-I electron transport ; Spectral characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Flavodoxin has been isolated and purified from cultures of the cyanobacterium Anabaena cultivated in a low-iron medium. This flavoprotein has a molecular weight of 20,000 and contains 1 molecule of flavin mononucleotide per mol of protein. Various biochemical characteristics are reported including amino-acid composition, isoelectric point and the fluorescence properties of the apoprotein. The extinction coefficients and isosbestic points were determined for the oxidized and semiquinone forms of flavodoxin. The electron paramagnetic resonance spectrum of the semiquinone exhibited a spectral linewidth of 23 G, which is typical for a neutral flavoprotein semiquinone. Kinetic measurements give a rate constant of 9.6×107 (M-1 min-1) for the reduction of flavodoxin in the photosynthetic electron-transport chain by the photosystem I and 6.6×106 for the reaction in which flavodoxin is reduced by ferredoxin-NADP+ oxidoreductase. The Michaelis constant for electron donation to nitrogenase by reduced flavodoxin is 8.5 μM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425156
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  • 9
    Electronic Resource
    Electronic Resource
    Consequences of the iron-dependent formation of ferredoxin and flavodoxin on photosynthesis and nitrogen fixation on Anabaena strains (1990)
    Springer
    Photosynthesis research 26 (1990), S. 119-125 
    Details
    ISSN: 1573-5079
    Keywords: Anabaena ; ferredoxin ; flavodoxin ; FPLC determination of ferredoxin and flavodoxin ; Iron deficiency ; Nitrogen fixation ; Photosynthesis ; strain differences in gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Iron-dependent formation of ferredoxin and flavodoxin was determined in Anabaena ATCC 29413 and ATCC 29211 by a FPLC procedure. In the first species ferredoxin is replaced by flavodoxin at low iron levels in the vegetative cells only. In the heterocysts from Anabaena ATCC 29151, however, flavodoxin is constitutively formed regardless of the iron supply. Replacement of ferredoxin by flavodoxin had no effect on photosynthetic electron transport, whereas nitrogen fixation was decreased under low iron conditions. As ferredoxin and flavodoxin exhibited the same Km values as electron donors to nitrogenase, an iron-limited synthesis of active nitrogenase was assumed as the reason for inhibited nitrogen fixation. Anabaena ATCC 29211 generally lacks the potential to synthesize flavodoxin. Under iron-starvation conditions, ferredoxin synthesis is limited, with a negative effect on photosynthetic oxygen evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00047083
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  • 10
    Electronic Resource
    Electronic Resource
    Attractiveness to mexican fruit flies of combinations of acetic acid with ammonium/amino attractants with emphasis on effects of hunger (1996)
    Springer
    Journal of chemical ecology 22 (1996), S. 499-511 
    Details
    ISSN: 1573-1561
    Keywords: Attractants ; Mexican fruit fly ; Diptera ; Tephritidae ; Anastrepha ludens ; ammonia ; methylamine ; putrescine ; acetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Ammonium acetate was more attractive than other ammonium salts to Mexican fruit flies (Anastrepha ludens) in an orchard test. We hypothesized that acetic acid enhanced the attractiveness of ammonia in the orchard test and that acetic acid may similarly enhance attractiveness of AMPu, an attractant consisting of a mixture of ammonium bicarbonate or ammonium carbonate, methylamine HCl, and putrescine. In laboratory experiments, acetic acid was attractive to flies deprived of either yeast hydrolysate or both sugar and yeast hydrolysate but not to flies fed both sugar and yeast hydrolysate. AMPu/acetic acid combinations were more attractive than AMPu alone to flies deprived of both sugar and yeast hydrolysate but not to flies fed sugar, regardless of yeast hydrolysate deprivation status. Acetic acid is the first attractant found that has become more attractive with both sugar and protein deprivation in studies withA. ludens. It is also the first that has enhanced the attractiveness of another attractant type. In orchard tests, yellow sticky panels baited with either AMPu or 17 mg of acetic acid were at least six times more attractive than unbaited panels. However, panels baited with both acetic acid (17–68 mg) and AMPu were less attractive than AMPu alone. These results differed from the laboratory data in which combinations were never less attractive than AMPu alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02033652
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