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  • Life and Medical Sciences  (155)
  • Wiley-Blackwell  (155)
  • American Geophysical Union
  • PANGAEA
  • 1990-1994  (155)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 220 (1994), S. 281-293 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Introverts of Priapulus caudatus and P. tuberculatospinosus bear 25 rows of scalids, as well as 8 spines and scattered papillae in the region the circumoral lip. These, as well as the first ring of pharyngeal teeth in P. tuberculatospinosus, are sensory organs. Although superficially they differ between species, they are all characterized by apical and/or subapical openings which are located on tiny cuticular tubules. All sensory organs contain cilia bearing bipolar receptor cells. The 8 sensory spines situated between the circumoral area and the beginning of the scalids are ultrastructurally similar to the scalids. The introvert and pharyngeal body walls, and associated muscles are described. © 1994 Wiley-Liss, Inc.
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  • 2
    ISSN: 0749-503X
    Keywords: Spontaneous mutagenesis ; repression and derepression of genes ; environmental effects ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Spontaneous mutation of some genes was studied in haploid adenine and leucine auxotrophic yeast Saccharomyces.It was shown that a decrease in the amount of adenine (from 500 to 0 mgl-1) or leucine (from 300 to 0·3 mgl-1) in the medium, simultaneously with the transition from repression to derepression of the biosynthesis of these metabolites, resulted in a 15- to 150-fold increase in the reversion rate of genes ade2 and leu2, respectively, for different strains. At the same time the mutation rate of suppressor genes varied relatively little (up to five-fold), and that of gene lys1 did not change at all. It was also demonstrated (on gene leu2) that the mutation rate is determined by the composition of the nutrient medium at the time of the S-phase of the cell cycle and it does not depend on the cultivation conditions during the presynthetic period.We discuss the hypothesis that derepressed genes mutate with a significantly higher rate than genes in the repressed state.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; yeast ; starch ; secretion ; extracellular glucoamylase ; feed-back control ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Three modes of production of the extracellular glucoamylase (GA) in Saccharomyces cerevisiae have been identified: repressed, basal and induced. The repressed mode is found with cells grown in rich media containing non-limiting concentrations of monosaccharides or disaccharides, including GA-hydrolysable maltose, as a sole carbon source. Both the basal and the induced modes (spanned by some seven-fold difference in the rate of GA production) can be displayed by either glucose-limited or glycerol- plus ethanol-consuming cultures: the induced mode is switched over to the basal one due to a feed-back inhibition by extracellularly accumulated GA. It is proposed that the feed-back control involved in GA production can be attenuated by starch which can thus ‘induce’ higher rates of GA production compared to the basal mode.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 0749-503X
    Keywords: Yeast ; protein export ; heat shock ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A new secreted yeast glycoprotein with an Mr of about 400 kDa (gp400) has been found. The glycoprotein is an O-mannosylated oligomer, whose synthesis and export into culture medium are stimulated by heat shock. Intracellular transport of gp400 is carried out by membrane vesicles distinct form the known constitutive scretory vesicles. Immunological analysis revealed gp400 only in Saccharomyces species.
    Additional Material: 12 Ill.
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  • 5
    ISSN: 0749-503X
    Keywords: Yeast ; vacuole ; H+-ATPase ; citrate transport ; ΔpH ; membrane potential ; growth phase ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Vacuoles were isolated from Yarrowia lipolytica yeast cells taken at various growth phases under carbon or nitrogen limitation. Vacuoles from the cells at the logarithmic growth phase showed a high activity of vacuolar H+-ATPase (0·9-1·1 U/mg protein) and efficiently generated chemical proton gradient and membrane potential across the tonoplast. Ca2+- and citrate transport were found to be maximal at this growth phase. At growth retardation and then in the stationary phase all the parameters studied decreased irrespective of the method of growth limitation. The citrate-transporting activity of vacuoles completely disappeared at growth retardation, also irrespective of the limitation method and irrespective of whether yeast cells overproduced citrate in the culture medium. The citrate-transporting system of Y. lipolytica vacuolar membrane is concluded not to be involved in citrate efflux and this efflux is probably performed by the plasmalemma transport system.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 12 (1991), S. 203-214 
    ISSN: 0197-8462
    Keywords: microwaves ; SHF ; mechanoreceptor ; temperature ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The effects of super high frequency (SHF) microwaves (34-78 GHz) on rates of spontaneous firing of the slowly adapting, stretch-receptor neurons of crayfish were studied. Initially, irradiation of continuously perfused, fluid-cooled preparations at power densities to 250 mW/cm2 caused a transient decrease in the rate of spontaneous firing (the dynamic response). Subsequently, with extinction of the SHF field, the rate of firing increased, finally stabilizing at pre-exposure levels (stationary phase). Rates of firing also increased when the receptor muscle was stretched, and they were inversely correlated with small, field-induced increases of temperature (∼1.5°C). The response to SHF radiation did not depend on frequency if temperature of the medium was constant. No resonant peaks were found when the millimeter range of frequencies was scanned.
    Additional Material: 13 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 49-65 
    ISSN: 0886-1544
    Keywords: fatty acid ; MHC ; MLC ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fatty acid 12(S)-HETE may be a new second messenger capable of activating PKC. In tumor cells 12(S)-HETE stimulates cytoskeleton-dependent cellular responses such as adhesion and spreading. Analysis of 12(S)-HETE effects on B16a melanoma cell cytoskeleton revealed reversible rearrangement of microtubules, microfilaments, the actin-binding proteins, vinculin, myosin heavy (MHC) and light chains (MLC), as well as bundling of vimentin intermediate filaments. The alterations in microfilaments and intermediate filaments occurred very rapidly, i.e., 5 min after exposure of tumor cells to 12(S)-HETE. The 12(S)-HETE-induced cytoskeletal alterations were accompanied by centrifugal organelle-translocation. Interestingly, MLC exhibited clear association with the cytoplasmic organelles. Biochemical analysis of the 12(S)-HETE effect indicated a PKC-mediated reversible hyperphosphorylation of MLC, vimentin, and a 130 kD cytoskeletal-associated protein. Optimal effects were obtained after 5 min treatment with 12(S)-HETE at 0.1 μM concentration. 12(S)-HETE pretreatment induced tumor cell spreading on a fibronectin matrix which required the intactness of all three major cytoskeletal components. The spreading process was dependent upon the activity of PKC. Our data suggest that 12(S)-HETE is a physiological stimulant of PKC. Further, it induces rearrangement of the cytoskeleton of tumor cells in interphase resulting in the stimulation of cytoskeleton-dependent cell activity such as spreading. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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  • 8
    ISSN: 0730-2312
    Keywords: herpes simplex virus ; high-density lipoproteins ; amphipathic helixes ; fusion-inhibitory peptides ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Apolipoprotein A-I (apoA-I), the major protein component of serum high-density lipoproteins (HDL), was found to inhibit herpes simplex virus (HSV)-induced cell fusion at physiological (∼ 1 μM) concentrations, whereas HDL did not exert any inhibitory effect. Lipid-associating, synthetic amphipathic peptides corresponding to residues 1-33 (apoA-I[1-33]) or residues 66-120 (apoA-I[66-120]) of apoA-I, also inhibited HSV-induced cell fusion, whereas a peptide corresponding to residues 8-33 of apoA-I (apoA-I[8-33]), which fails to associate with lipids, did not exert any inhibitory effect. These results suggest that lipid binding may be a prerequisite for peptide-mediated fusion inhibition. Consistent with this idea, a series of lipid-binding 22-amino-acid-residue-long synthetic amphipathic peptides that correspond to the amphipathic helical domains of apoA-I (A-I consensus series), or 18-residue-long model amphipathic peptides (18A series), were found to exert variable levels of fusion-inhibitory activity. The extent of fusion-inhibitory activity did not correlate with hydrophobic moment, hydrophobicity of the nonpolar face, helix-forming ability, or lipid affinity of the different peptides. Peptides in which the nonpolar face was not interrupted by a charged residue displayed greater fusion-inhibitory activity. Also, the presence of positively charged residues at the polar-nonpolar interface was found to correlate with higher fusion-inhibitory activity.
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 31 (1992), S. 42-47 
    ISSN: 1040-452X
    Keywords: Casein kinase II ; Heat shock ; Posttranslational regulation ; Protein synthesis ; Cotton parasite ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A homogeneous preparation of casein kinase 2 has been isolated from the phytopathogenic fungus Verticillium dahliae (the parasite of cotton). The enzyme consists of three subunits with molecular masses of 53, 41, and 38 kDa. Highly specific immune serum against casein kinase 2 has been obtained. By means of immunoblotting, enzyme-linked immunosorbent assay (ELISA), and immunochemical isolation on protein A-Sepharose, it is shown that the amount of casein kinase 2 increases under heat shock conditions (at least in part due to the synthesis de novo), while the synthesis of the majority of other proteins falls. The activity of casein kinase 2 is supressed during heat shock and so does not correlate with its content. The results give an evidence for the two-step model of casein kinase 2 regulation during heat shock.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 39 (1994), S. 1-7 
    ISSN: 1040-452X
    Keywords: Testis ; Ovotestis ; True hermaphrodite ; Mullerian duct ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Sertoli cell secretion of Mullerian-inhibiting substance (MIS) begins shortly after testis differentiation. Mullerian ducts regress following MIS exposure during an embryonic critical period. In dogs with XX sex reversal, Mullerian ducts persist in the presence of testicular tissue. This study was conducted to determine whether MIS is present in ovotestes of XX sex-reversed embryos during the period for Mullerian duct regression in normal males. XX sex-reversed embryos and normal littermates were identified by a combination of karyotype and gonadal histology. The degree of regression in the adjacent Mullerian duct was scored. Immunohistochemical staining was used to detect MIS in the contralateral gonad. Testicular differentiation and MIS secretion were identified in XY embryos at all ages studied (35-46 days). Seminiferous tubules were not observed in gonads of embryos at risk of XX sex reversal between 35-38 days (n = 15), but were observed at 40 and 46 days (n = 3). Although positive staining for MIS was observed in ovotestes, adjacent Mullerian ducts persisted. The degree of seminiferous tubule development was reduced and MIS secretion was delayed in ovotestes, compared to normal testes. Mullerian duct persistence in this model is apparently due to an abnormality in the quantity and timing of MIS secretion during embryonic development.© 1994 Wiley-Liss, Inc.
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