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  • 1995-1999  (3,777)
  • 1960-1964  (101)
  • 1945-1949  (9)
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  • 11
    Electronic Resource
    Electronic Resource
    Molecular characterization of a novel peroxidase isolated from the ligninolytic fungus Pleurotus eryngii (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A haem peroxidase different from other microbial, plant and animal peroxidases is described. The enzyme is secreted as two isoforms by dikaryotic Pleurotus eryngii in peptone-containing liquid medium. The corresponding gene, which presents 15 introns and encodes a 361-amino-acid protein with a 30-amino-acid signal peptide, was isolated as two alleles corresponding to the two isoforms. The alleles differ in three amino acid residues and in a seven nucleotide deletion affecting a single metal response element in the promoter. When compared with Phanerochaete chrysosporium peroxidases, the new enzyme appears closer to lignin peroxidase (LiP) than to Mn-dependent peroxidase (MnP) isoenzymes (58–60% and 55% identity respectively). The molecular model built using crystal structures of three fungal peroxidases as templates, also showed high structural affinity with LiP (Cα-distance 1.2 Å). However, this peroxidase includes a Mn2+ binding site formed by three acidic residues (E36, E40 and D175) near the haem internal propionate, which accounts for the ability to oxidize Mn2+. Its capability to oxidize aromatic substrates could involve interactions with aromatic residues at the edge of the haem channel. Another possibility is long-range electron transfer, e.g. from W164, which occupies the same position of LiP W171 recently reported as involved in the catalytic cycle of LiP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01164.x
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  • 12
    Electronic Resource
    Electronic Resource
    Characterisation of symbiotically efficient alfalfa-nodulating rhizobia isolated from acid soils of Argentina and Uruguay (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 28 (1999), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The diversity, growth and symbiotic behaviour of symbiotically efficient alfalfa-nodulating rhizobia isolated from acid soils of Argentina and Uruguay were analysed. Partial sequencing of the 16S rDNA indicated that these isolates belong to Sinorhizobium meliloti species. IS-fingerprinting analysis revealed a high diversity among the isolates but some of them appear related to inoculant strains currently used in the region. The S. meliloti isolates showed a decreased growth rate with increasing acidity. They were, however, able to nodulate alfalfa at pH 5.6, but showed a delayed nodulation and decreased nodule number typical of S. meliloti strains. The impaired nodulation of S. meliloti at pH 5.6 did not result in a reduction of alfalfa dry matter production or nitrogen content. However, significant differences were observed for the relative symbiotic effectiveness of the strains analysed. LPU63 (Argentina) was the most effective among the isolates and exhibited a high nodulation competitiveness at both neutral and acidic pH. These results suggest that the isolate LPU63 may be a potential efficient inoculant for alfalfa in acid soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1999.tb00572.x
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  • 13
    Electronic Resource
    Electronic Resource
    Molecular evidence supporting the existence of two major groups in uropathogenic Escherichia coli (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 14 (1996), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Abstract Molecular methods allow an extremely fine strain typing that can be used to establish the population structure of bacterial species. This methodology has been used to characterize a collection of 74 uropathogenic Escherichia coli obtained from three hospitals located in geographically distant towns in Spain, some representatives of the ECOR collection and other reference strains. Genomic DNA was analyzed by RAPD (Random Amplified Polymorphic DNA) that can characterize a bacterial strain to the level of defining individual clones. The 16S rDNA-23S rDNA spacers were amplified by PCR and submitted to restriction analysis. Finally, the presence or absence of G adhesins in Escherichia coli as well as the type of adhesin (three types are known) have been shown by PCR amplification followed by digestion with restriction enzymes. As expected a wide diversity was shown by RAPD and identical patterns were only found in the case of strains isolated from the same individual, an obvious case of relapse. Analysis of the spacers' restriction patterns showed the presence of two markedly differentiated clusters that we have named α and ß. Both RAPD and spacer restriction patterns originated similar clusters of strains showing a consistency in the evolution of the global genome with the sequence variation of the ribosomal spacers. Furthermore, most of the strains having G-adhesin, with only a few exceptions, corresponded to the α rRNA spacer group. The two spacer types detected were also consistent with some phenotypic markers such as sucrose and raffinose utilization. The α and β clusters could be intraspecific groups produced by partial sexual isolation or other barriers that are originating a divergent evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-695X.1996.tb00291.x
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  • 14
    Electronic Resource
    Electronic Resource
    An acylcyclohexadione retardant inhibits gibberellin A1 metabolism, thereby nullifying phytochrome-modulation of cowpea epicotyl explants (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 94 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The regulation by phytochrome of stem elongation in light-grown plants depends on gibberellins (GAs). To investigate whether this is mediated by a change in GA metabolism, the effect of the GA biosynthesis inhibitor LAB 198 999 (an acylcyclohexadione derivative) on the end-of-day far-red (FR) response in cowpea (Vigna sinensis L.) epicotyl explants has been investigated. Growth of epicotyl explants of light-grown seedlings was enhanced when treated with far-red light before incubation in the dark (end-of-day FR effect). Low doses of LAB 198 999 (0.05 and 0.5 μg explant−1) reduced the effect of FR, whereas 5 to 50 μg explant−1 stimulated elongation of both red light (R)- and FR-treated epicotyl explants while nullifying the differences between R and FR treatments. In paclobutrazol-treated epicotyl explants, FR enhanced the response to applied GA1 and GA20, whereas LAB 198 999 increased the activity of GA1 and decreased that of GA20, [3H]Gibberellin A1, injected into the basal part of the epicotyl, was transported and metabolized mainly to [3H]GA8 in the apical 20 mm of the epicotyl. The conversion of [3H]GA1 to [3H]GA8 was dramatically reduced by both end-of-day FR treatments and LAB 198 999 applications. In addition, both treatments enhanced epicotyl elongation. It is proposed that the regulation of cowpea epicotyl growth by phytocrome is mediated, at least partially, by modifying GA1 degradation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00988.x
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  • 15
    Electronic Resource
    Electronic Resource
    Influence of Skeletal Site of Origin and Donor Age on Osteoblastic Cell Growth and Differentiation (1999)
    Springer
    Calcified tissue international 64 (1999), S. 280-286 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Human osteoblastic cells — Skeletal site — Aging.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Bone loss with aging may be due, at least in part, to inadequate bone formation. Moreover, the process of bone aging is known to follow a different pattern throughout the skeleton. In this study, we examined the cell proliferation rate (area under the cell growth curve, AUC) and the secretion of C-terminal type I procollagen (PICP), alkaline phosphatase (ALP), and osteocalcin (OC) in primary cultures of osteoblastic cells from human trabecular bone. Osteoblastic cells were obtained for 168 donors (100 women and 68 men). Ninety-eight bone samples were obtained from subjects undergoing knee arthroplastia, 52 aged 50–70 years (64 ± 5) and 46 over age 70 (73 ± 2). Another 70 bone samples were obtained from subjects undergoing hip arthroplastia; 51 were 50–70 years old (64 ± 4) and 19 were over 70 (75 ± 5). Osteoblastic cells from the older donors had a lower proliferation rate and OC secretion than those from younger subjects. However, ALP secretion was higher in the former subjects, whereas PICP secretion was unchanged. Osteoblastic cells from hip had a lower proliferation rate than those from knee. PICP secretion was also lower and ALP secretion was higher in the former cells. In age-matched cell cultures, osteoblastic cells from the knee had higher proliferation rate and PICP secretion than osteoblastic cells from the hip. However, ALP secretion was lower in knee osteoblastic cells than those from hip only in the younger group. With aging, ALP secretion was found to increase in knee osteoblactic cells, whereas OC secretion decreased in osteoblastic cell cultures from the hip. Our findings suggest that bone loss with aging may be accounted for, at least in part, by a decreased osteoblastic cell proliferation and an increased osteoblastic maturation. In addition, our data indicate that these changes with aging do not occur similarly at different skeletal sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900619
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  • 16
    Electronic Resource
    Electronic Resource
    Effect of carbon source and pH of the growth medium on spore germination in Phycomyces blakesleeanus (1995)
    Springer
    Archives of microbiology 164 (1995), S. 231-234 
    Details
    ISSN: 1432-072X
    Keywords: Key words Spore activation ; Phycomyces ; Carbon source ; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phycomyces blakesleeanus sporangiospores responded differently to activation by physical and chemical stimuli. Spores that were physically (heat shock) activated or chemically (ammonium acetate) activated germinated and grew at pH 4.5 with the hexoses glucose, fructose, galactose, and N-acetylglucosamine, and with glycerol and amino acids. Under these conditions, physically activated spores showed a lower, although significant growth with the hexoses fructose, galactose, N-acetylglucosamine and with glycerol. On the other hand, physically activated spores incubated at alkaline pH (pH 7.3) required glucose to germinate; a requirement not observed with chemically activated spores, which showed significant growth in the other hexoses tested. Both physically and chemically activated spores incubated at pH 7.3 were unable to germinate and grow with amino acids and glycerol. These results suggest that there are different targets for activation of the spores by physical and chemical treatments. The levels of the fermentative enzymes alcohol dehydrogenase and lactate dehydrogenase and of the oxidative enzyme NAD+-isocitrate dehydrogenase were higher in cells grown at pH 4.5 in medium containing glucose; however, alcohol dehydrogenase and lactate dehydrogenase appear not to be affected by a change in the pH of the growth medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050259
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  • 17
    Electronic Resource
    Electronic Resource
    Persistent behavior in a phase-shift sequence of periodical biochemical oscillations (1998)
    Springer
    Bulletin of mathematical biology 60 (1998), S. 689-702 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We present the analysis of a phase-shift sequence obtained from random transitions between periodic solutions of a biochemical dynamical model, formed by a system of three differential equations and which represent an instability-generating multienzymatic mechanism. The phase-shift series was studied in terms of Hurst’s rescaled range analysis. We found that the data were characterized by a Hurst exponent H = 0.69, which was clearly indicative of long-term trends. This result had a high significance level, as was confirmed through Monte Carlo simulations in which the data were scrambled in the series, destroying its original ordering. For these series we obtained a Hurst exponent which was consistent with the expectation of H = 0.5 for a random independent process. This clearly showed that, although the transitions between the periodic solutions were provoked randomly, the stochastic process obtained exhibited long-term persistence. The fractal dimension was also estimated and found to be consistent with the value of the Hurst exponent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1006/bulm.1997.0036
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  • 18
    Electronic Resource
    Electronic Resource
    Mutational analysis of the MPZ, PMP22 and Cx32 genes in patients of Spanish ancestry with Charcot-Marie-Tooth disease and hereditary neuropathy with liability to pressure palsies (1997)
    Springer
    Human genetics 〈Berlin〉 99 (1997), S. 746-754 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Charcot-Marie-Tooth disease (CMT) and hereditary neuropathy with liability to pressure palsies (HNPP) are two inherited peripheral neuropathies. The most prevalent mutations are a reciprocal 1.5-Mb duplication and 1.5-Mb deletion, respectively, at the CMT1A/HNPP locus on chromosome 17p11.2. Point mutations in the coding region of the myelin genes, peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ) or connexin 32 (Cx32) have been reported in CMT patients, including CMT type 1 (CMT1), CMT type 2 (CMT2) and Déjérine-Sottas neuropathy (DS) patients, and only in the coding region of PMP22 in HNPP families lacking a deletion. We have investigated point and small mutations in the MPZ, PMP22 and Cx32 genes in a series of patients of Spanish ancestry: 47 CMT patients without duplications, and 5 HNPP patients without deletions. We found 15 different mutations in 16 CMT patients (34%). Nine different mutations in ten patients were detected in the Cx32 gene, this being the most frequently involved gene in this series, whereas five mutations involved the MPZ gene and only one the PMP22 gene. Six out of nine nucleotide substitutions in the Cx32 gene involved two codons encoding arginine at positions 164 and 183, suggesting that these two codons may constitute two Cx32 regions prone to mutate in the Spanish population. Analysis of HNPP patients revealed a 5′ splicing mutation in intron 1 of the PMP22 gene in a family with autosomal dominance, which confirms allelic heterogeneity in HNPP. Ectopic mRNA analysis on leukocytes suggests that this mutation might behave as a null allele.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004390050442
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  • 19
    Electronic Resource
    Electronic Resource
    Leishmania infantum Nicolle, 1908 from southern Spain: Characterisation of the strains from human visceral and cutaneous leishmaniasis and from sandflies; with a numerical analysis of the isoenzymatic data (1996)
    Springer
    Systematic parasitology 33 (1996), S. 177-182 
    Details
    ISSN: 1573-5192
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This study presents the results of the characterisation of 17 strains ofLeishmania by isoenzyme electrophoresis from a focus of leishmaniasis in southern Spain: two from human visceral leishmaniasis, four from human cutaneous leishmaniasis and 11 from sandflies. The 17 strains are grouped in 6 zymodemes characterised by their variability as regards to the electrophoretic mobility of the enzymes MDH, G6PD, NP and ME. Thus, we confirm the high intraspecific variability ofLeishmania (L.) infantum in a focus of southern Spain, as already suggested by previous studies. Zymodemes GR-15 and GR-17 are also described for the first time in Spain, and they characteristically possess the same relative electrophoretic mobility in the enzyme ME (93). Sixteen zymodemes of theL. infantum complex found in southern Spain were numerically analysed on the basis of the enzymatic profiles of 122Leishmania strains characterised from this area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01531198
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  • 20
    Electronic Resource
    Electronic Resource
    Cubic CdS thin films studied by spectroscopic ellipsometry (1997)
    Springer
    Journal of materials science 8 (1997), S. 399-403 
    Details
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract CdS polycrystalline films were grown onto glass substrates by chemical bath deposition (CBD) and characterized by spectroellipsometry, X-ray diffraction and transmission electron microscopy. The X-ray diffraction patterns of the samples showed the presence of a CdS cubic phase (β-CdS) and of Cd2SiO4 as interfacial material. Using electron diffraction it was possible to index the films as cubic CdS. From effective dielectric function measurements and from reported optical data for the dielectric function of cubic CdS crystals, grown by vapour phase epitaxy, it was possible to fit the experimental data to an effective medium approximation, and to deduce the film thickness, the void fraction and the field screening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018555826924
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