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  • 1
    Electronic Resource
    Electronic Resource
    Stabilization of chitin synthetase and purification of chitosomes from several mycelial Mucorales (1987)
    Springer
    Antonie van Leeuwenhoek 53 (1987), S. 171-181 
    Details
    ISSN: 1572-9699
    Keywords: Chitin synthetase ; chitosomes ; Mucorales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Stability of chitin synthetase in cell-free extracts from mycelial fungi was markedly improved by the presence of sucrose in the homogenization media. Breakage of mycelium in sucrose-containing buffer yielded enzyme preparations from which chitosomal chitin synthetase could be purified by a procedure involving ammonium sulfate precipitation, gel filtration and centrifugation in sucrose density gradients. Purified chitosomes catalyzed the synthesis of chitin microfibrils in vitro upon incubation with substrate and activators. Chitosomal chitin synthetase from the filamentous form of M. rouxii was similar to the enzyme from yeast cells, except for the poorer stability and diminished sensitivity to GlcNAc activation of the former.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393845
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  • 2
    Electronic Resource
    Electronic Resource
    Sticky model of charged colloids (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 703-709 
    Details
    ISSN: 0392-6737
    Keywords: Theory and models of liquid structure ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We use the Sticky Electrolyte Model, which we solved before in PY/MSA, to obtain the equation of state of a charge colloid taking into account both sticky and charge contribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02456715
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  • 3
    Electronic Resource
    Electronic Resource
    Nectar thievery by ants from southern Spanish insect-pollinated flowers (1984)
    Springer
    Insectes sociaux 31 (1984), S. 142-154 
    Details
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Resume On a étudié quelques facteurs liés à la consommation du nectar chez les fourmis dans un échantillon de 75 espèces de plantes du sud de l'Espagne qui sont pollinisées par des insectes et qui produisent du nectar. Les fourmis exploitent le nectar de façon opportuniste. La variation entre les espèces de plantes en ce qui concerne le taux de sécrétion de nectar et la localisation des fleurs par rapport au sol n'a pas d'incidence, pas plus que la possibilité de visite par les fourmis ni l'identité des espèces enregistrées. Les restrictions mécaniques à l'accessibilité du nectar (corolles tubulaires, structures fermées) diminuent la consommation de nectar par les fourmis. Quelques tendances évolutives dans la morphologie florale, habituellement liées à une augmentation de la spécificité des pollinisateurs, peuvent être interprétées simultanément en termes de meilleure adaptation des plantes pour exclure des insectes non pollinisateurs qui profitent du nectar.
    Notes: Summary Correlates of ant nectarivory have been investigated in a sample of 75 insect-pollinated, nectar-producing southern Spanish plant species. Ants exploit floral nectar opportunistically. Variation among plant species in sugar secretion rates and flower location relative to ground level do not influence either the chances of ant visitation or the identity of ant species involved. Mechanical restrictions on nectar accessibility (tubular corollas, occlusive structures) decrease nectar thievery, Some evolutionary trends in floral morphology usually related to a decrease in the range of effective pollinators alone may simultaneously be interpreted in terms of increased plant adaptedness to exclude non-pollinating insect nectarivores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02232711
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  • 4
    Electronic Resource
    Electronic Resource
    An examination of factors affecting the instability of Saccharomyces cerevisiae glucan synthetase in cell free extracts (1984)
    Springer
    Archives of microbiology 137 (1984), S. 209-214 
    Details
    ISSN: 1432-072X
    Keywords: Saccharomyces cerevisiae ; Glucan synthetase ; EDTA ; Magnesium ; Sucrose ; Fluoride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Yeast β(1–3) glucan synthetase is stimulated and stabilized by EDTA. Sucrose protects the enzyme from selfinactivaton. Preincubation of cell free extracts at low sucrose concentrations indicates a slow transition of the enzyme towards dissociation. Transition kinetics at 30° C and 0° C in the presence and in the absence of sucrose are interpreted assuming that a subunit is thermolabile in the free state and that sucrose increases its stability. Magnesium is deletereous for glucan synthetase in cell-free extracts. Chaotropic agents inactivate glucan synthetase according to their capacity to solubilize and depolymerize biological compounds. Fluoride plays a special role in the activation of glucan synthetase. Its action appears to be dependent on the presence of GTP (or other nucleotides). The role of all these agents on the activity and stability of the enzyme is interpreted in a unified scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414545
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  • 5
    Electronic Resource
    Electronic Resource
    Activation of chitin synthetase from Phycomyces blakesleeanus by calcium and calmodulin (1987)
    Springer
    Archives of microbiology 148 (1987), S. 280-285 
    Details
    ISSN: 1432-072X
    Keywords: Chitin synthetase ; Phycomyces blakesleeanus ; Calcium-calmodulin ; Proteases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Levels of basal chitin synthetase in cell-free extracts from Phycomyces blakesleeanus were reduced by breakage of cells in the presence of EDTA or EGTA. Addition of Ca2+ to these extracts activated chitin synthetase. Maximal activation was obtained after 2 h at a Ca2+ concentration of 2–5 mM. Activation by calcium was not reduced by any protease inhibitor tested but benzamidine, whereas the weak proteolytic activity of the extracts was inhibited by antipain. Larger levels of chitin synthetase activation were obtained by the simultaneous addition of calcium and calmodulin in most, but not all extracts. This further activation by calmodulin was prevented by TFP. ATP or cAMP did not stimulate activation by calcium or calcium-calmodulin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00456705
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  • 6
    Electronic Resource
    Electronic Resource
    Separation of chitosomes and secretory vesicles from the “slime” variant of Neurospora crassa (1987)
    Springer
    Archives of microbiology 149 (1987), S. 156-162 
    Details
    ISSN: 1432-072X
    Keywords: “Slime” variant ; Neurospora ; Chitosomes ; Chitin synthetase ; Secretory vesicles ; Invertase ; Phosphatase ; Membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cells from the “slime” variant of Neurospora crassa were broken in isotonic conditions by use of triethanolamine buffer plus EDTA. After removal of large membranous structures by low-speed centrifugation, chitosomes and secretory vesicles were separated by means of gel filtration, precipitation of membranous contaminants with Concanavalin A, and centrifugation in sucrose or glycerol gradients. Polypeptidic composition of fractions enriched in secretory vesicles or chitosomes was found to be distinct. By these criteria we concluded that chitosomes and secretory vesicles represent different populations of microvesicles. Both microvesicular populations appeared free of endoplasmic reticulum and vacuolar contaminants as demonstrated by determination of appropriate enzymatic markers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425082
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  • 7
    Electronic Resource
    Electronic Resource
    Inhibition of the yeast-mycelial transition and the phorogenesis of Mucorales by diamino butanone (1988)
    Springer
    Archives of microbiology 151 (1988), S. 10-14 
    Details
    ISSN: 1432-072X
    Keywords: Mucor ; Phycomyces ; Diaminobutanone ; Polyamines ; Dimorphism ; Phorogenesis ; Ornithine decarboxylase ; Fungal differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diamino butanone (DAB), a competitive inhibitor of ornithine decarboxylase (ODC) a key enzyme in polyamine biosynthesis, inhibited the yeast to hyphae transition in Mucor rouxii, induced by transfer from anaerobiosis to aerobiosis, but not the opposite phenomenon. Addition of DAB to anaerobic yeast cells brought about a decrease in ODC and polyamine levels. In these conditions, the aerobic shift produced only a weak increase in ODC activity and no change in polyamine levels. DAB also blocked phorogenesis in M. rouxii and in Phycomyces blakesleeanus. At the effective concentrations DAB did not affect cell growth of either fungus. It is suggested that low, constant levels of ODC and polyamines are necessary for cell growth, and that high transient levels are required during the differentiative steps. DAB, at the concentrations used, affects this last process, but does not interfere with the maintenance level of polyamines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00444661
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of a proteinaceous extracellular coat synthesized by the “slime” variant of Neurospora crassa (1989)
    Springer
    Archives of microbiology 152 (1989), S. 25-32 
    Details
    ISSN: 1432-072X
    Keywords: Neurospora crassa ; “Slime” variant ; Cell coat ; Exocellular proteins ; Glycoproteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cells of the “slime” strain of Neurospora crassa synthesize a coherent extracellular material which remains attached to the cell surface, but is released into the liquid medium by shaking. The material was purified and studied by different criteria. By electron microscopy it appears as long wavy sheets which strongly bind concanavalin A, but not wheat germ agglutinin, and maintain their integrity in the absence of structural polysaccharides. Analysis of the purified material revealed that it was free of contaminating membranes; it contained more than 70% protein, 1% neutral sugars (glucose, mannose, fucose and galactose), less than 2% lipids and ca. 4% not-characterized hexosaminelike compounds. Its polypeptide pattern as determined by PAGE was complex. The significance of this material is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00447007
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  • 9
    Electronic Resource
    Electronic Resource
    Self-assembly properties of the proteinaceous coat secreted by the “slime” variant of Neurospora crassa (1989)
    Springer
    Archives of microbiology 152 (1989), S. 33-38 
    Details
    ISSN: 1432-072X
    Keywords: Neurospora crassa ‘Slime” variant ; Cell coat ; Glycoproteins ; Self-assembling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The proteinaceous extracellular material (PEM) synthesized by the cells of the ‘slime” strain of Neurospora crassa (see Martinez et al. 1989) was solubilized by treatment with urea or guanidine. Removal of these chemicals by dialysis, caused reassembly of the solubilized proteins into material with the same microscopic appearance as the original PEM. Polypeptide patterns from both native and reassembled structures were identical. Dialysis-mediated reassembly of the solubilized proteins appeared to be dependent on both concentration of the soluble macromolecules and time. Gel chromatography of PEM solubilized with different agents revealed two discrete populations of complexes with molecular masses of 1,500 and 500 kDa respectively. These were able to reassemble into lamellar structures with a variable degree of efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00447008
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  • 10
    Electronic Resource
    Electronic Resource
    Subcutaneous and intramuscular implantation of sepiolite-collagen complexes (1992)
    Springer
    Journal of materials science 3 (1992), S. 239-244 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The tissue response after subcutaneous or intramuscular implantation of sepiolite-collagen complexes has been studied. These implants form a continuous three-dimensional matrix, showing a fibrous and rough surface topography. The host tissue response against the collagen-sepiolite complexes is a foreign-body reaction, focally intense, with abundant giant cells, typical of resorbable biomaterials. Sepiolite-collagen complex (SC) appears to be well tolerated and almost entirely resorbed within most of the experimental lesions. Sepiolite-collagen complex cross-linked with glutaraldehyde (SCG) demonstrates a significantly greater resistance to biodegradation than the non-cross-linked product. The anti-bovine collagen antibody levels in the sera of implanted rats were studied. The subcutaneous implantation of SC complexes induces a low immunological reaction, while it is almost negligible for the SCG ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705287
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