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  • 1995-1999  (1,181)
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  • 1
    ISSN: 1434-1948
    Keywords: Imidazaboles ; Carbene-borane adducts ; Azole-borane adducts ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation and characterization of five new imidazabole derivatives is reported: 1,5-dibenzyl-4,4,8,8-tetrahydroimidazabole (2), 4,4,8,8-tetrafluoro-1,5-dimethylimidazabole (3), 4,4-difluoro-8,8-dihydro-1,5-dimethylimidazabole (4), 4,4,8,8-tetrachloro-1,5-dimethylimidazabole (5), and 4,4,8,8-tetraethyl-1,5-dimethylimidazabole (6). The structures of compounds 2-6 as dimeric carbene-borane adducts rather than dimeric N-borane adducts are discussed on the basis of NMR (2-6) and X-ray diffraction data (2, 3, 5 and 6).
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  • 2
    ISSN: 1572-8854
    Keywords: X-ray diffraction ; xanthenedione ; heterocyclic fused rings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Several 9-(2-R phenyl)xanthenediones have been synthesized and the x-ray diffraction structure for the 2-methylphenyl derivative (4b) has been determined. This compound crystallizes in the monoclinic system, space group P21/n, with a = 11.729 (3), b = 9.674 (3), c = 14.628 (4) Å, and β = 106.30°. It presents a partially hydrogenated xanthene system in distorted boat conformation for the heterocyclic central ring, and an almost ideal envelope conformation for the outer rings. The aromatic substituent at the ninth position is at 84° in angle with the xanthene system.
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  • 3
    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.
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  • 4
    ISSN: 1432-2242
    Keywords: Key words Vitis vinifera ; AFLPs ; Cultivar identification ; Clone identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  AFLPs were used to characterize 67 different grapevine accessions from a collection of D.O.Ca. Rioja in Spain. A correct selection of primers and selective nucleotides allowed us to maximize the number of amplified fragments analyzed per reaction yielding an average of 100 per reaction, 49% of which were polymorphic. Based on the presence or absence of amplified fragments for each genotype resulting from a reaction with two primer combinations, we have established the genetic similarity between the different accessions in the collection. These results allowed us to resolve different genotypes maintained under the same name (homonyms) and to identify the same genotype under different names (synonyms) thus permitting the elimination of redundant germplasm. Furthermore, by providing information on more than 50 polymorphic loci per reaction, a few reactions were sufficient to identify distinct AFLP patterns characteristic of specific clones, with different agronomic and organoleptic features, belonging to the same cultivar. The possibility for clonal identification, shown here for grapevines, can have important implications in the protection and management of clonal selections.
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  • 5
    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.
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  • 6
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A method based on neutron activation analysis was developed for the determination of fractions of milligrams of 2,4-D (2,4-dichlorophenoxy acetic acid) in aqueous solution in laboratory tests. The indirect determination of 2,4-D was based on the quantification of chlorine,38Cl, produced by neutron activation. The range of application was 0.01–100 mg l−1. No loss of38Cl by chemical effects of the nuclear reaction was found. The advantages of the proposed method include high precision and sensitivity of determination. Results were compared with those obtained by UV-Vis spectrophotometry, where concentrations less than 1 mg·l−1 were not detected.
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  • 7
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Gamma exposure rate and radon levels were measured in 75 single-family dwellings in Mexico City in order to correlate them with local environment. Radon monitoring was performed both indoors and outdoors using a continuous working level monitor for short-lived radon decay products; the gamma exposure rate was measured using CaSO4: Dy+PTFE. The results obtained show a log-normal distribution. The mean indoor radon concentration is lower than 45 Bq/m3 and the mean indoor gamma exposure rate was 11.29 μR/h.
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  • 8
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Humoral and cellular immune responses to Fasciola hepatica excretory-secretory products (ESPs) in primary and secondary experimental infections in goats were studied. Primary infection induced the development of chronic subclinical fascioliasis that did not affect the establishment of flukes coming from the secondary infection, as the same percentages of recovered flukes were found in both groups. The specific IgG response to F. hepatica ESPs was similar in primary and secondary infections; challenge flukes did not induce any modification in the IgG response. The specific lymphocyte response to F. hepatica ESPs was absent in most of the infected goats, both primarily and secondarily infected. A modulation of the nonspecific cellular responses to mitogens was also observed. All infected goats showed a reduced proliferative response to concanavalin A and phytohemagglutinin. According to our results, humoral and cellular responses to F. hepatica ESPs in goats have no protective effect on the establishment of flukes and the development of disease in either primary or secondary infections.
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  • 9
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Liver invasion by amebas with production of amebic liver abscess (ALA) is the most common extraintestinal lesion produced by the protozoan parasite Entamoeba histolytica. This hepatic damage is characterized by the presence of extensive tissue necrosis. However, little is known about the parasite and host factors involved in the process of tissue damage. During the early establishment of amebas in the liver parenchyma as well as during the extension of the tissue necrosis, parasites interact with sinusoidal endothelial cells. As a consequence of ameba-endothelial cell interactions, the latter can be activated and express proinflammatory factors that could be related to tissue destruction. We studied by immunohistochemistry the localization of antigenic molecules of E. histolytica trophozoites and of molecules such as intercellular adhesion molecule 1 (ICAM-1), ICAM-2, and von willebrand factor in activated endothelial cells of human ALA, which could be related to the pathophysiological mechanisms of tissue destruction in amebiasis.
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  • 10
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Two protein bands with laccase activity were found after PAGE of culture liquid or mycelium extract of Pleurotus eryngii, grown on glucose–ammonium tartrate–yeast extract medium with and without inducers. A major and a minor laccase band were observed in the basal medium. The intensity of the major band (laccase I) did not change after the addition of inducers. However, the minor band (laccase II), characterized by higher electrophoretic mobility, was strongly induced by wheat–straw alkalilignin and vanillic and veratric acids. Laccase activity in the basal medium had an optimum pH of 4.5 and was stable from pH 3 to 10 during 24 h at room temperature. This enzyme had wide substrate specificity on hydroquinones, methoxy-substituted monophenols, and aromatic amines. In general, laccase activity was found only with compounds having a redox potential lower than 0.5 mV. The highest activity was obtained with methoxy- and methyl-substituted p-hydroquinones and aromatic diamines. Some activity also occurred with the aliphatic compound 3,5-cyclohexadiene-1,2-diol.
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