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  • Springer  (91)
  • 1990-1994  (91)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    The formation of intercellular junctions in insect stem cell progeny (cockroach intestinal epithelium) (1991)
    Springer
    Development genes and evolution 200 (1991), S. 277-288 
    Details
    ISSN: 1432-041X
    Keywords: Insect epithelia ; Developing junctions ; Epithelial differentiation ; Gap junctions ; Septate junctions ; Proliferative stem cells ; Periplaneta americana (Blattidae)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The stages in the development of intercellular junctions have been followed in the mesenteric caecal cells of the cockroach midgut, where two types of mature cell, the columnar and the secretory, exist. ‘Nests’ of undifferentiated replacement cells occur at intervals along the basal lamina, consisting of central, dividing cells and peripheral semi-lunar cells; the former act as proliferative stem cells to give rise to either pre-columnar or pre-secretory cells. The semi-lunar cells are pre-columnar and produce an attenuated process which gradually projects up to the luminal surface, producing microvilli and a dense extracellular substance en route. Intercellular gap junctions appear between these maturing columnar cell borders first, while septate junctions differentiate later; these are assembled from two different sets of intramembranous particle which become organized into either plaques or rows in parallel alignment, possibly mediated by actin filaments and microtubules. The pre-secretory cells, which are much fewer in number, remain associated only with the basal lamina and never reach the lumen; they develop into one of three distinct mature secretory cell types which release their secretory product in different ways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241297
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  • 2
    Electronic Resource
    Electronic Resource
    Intermediate filament protein expression and mesoderm formation in the rabbit embryo (1992)
    Springer
    Development genes and evolution 201 (1992), S. 45-60 
    Details
    ISSN: 1432-041X
    Keywords: Gastrulation ; Cytokeratins ; Vimentin ; Immunofluorescence ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study aims to describe the regulation of vimentin and cytokeratin expression during differentiation of primary mesenchymal cells in the 7 day old rabbit embryo; unusual intermediate filament protein expression patterns have already been found in this species at later embryonic stages. Double-labelling indirect immunofluorescence assays with a panel of monoclonal intermediate filament antibodies are performed on frozen sections and compared with aldehyde-fixed plastic-embedded tissues. The histological part of the study, serving as a basis for the topographical orientation in the immunostained frozen sections, emphasises many similarities between the primitive streak embryos of the rabbit and the chick. The immunohistochemical analysis reveals cytokeratin expression to varying degrees in all germ layers. Vimentin expression, always in combination with cytokeratin expression, is found in a few cells of the ectoderm, endoderm and lateral mesoderm, but not in the primary mesenchymal cells of either the primitive node or the primitive streak. The results are discussed in relation to recent experimental findings on differentiation and morphogenetic processes in the primitive streak embryo. While these complex expression patterns make it seem unlikely that intermediate filament protein subtypes are expressed independently of cellular function during development, no indication can be found for a relation between vimentin expression and the morphogenetic changes thought to be important during mesoderm formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188775
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  • 3
    Electronic Resource
    Electronic Resource
    Artificial worlds and economics, part I (1993)
    Springer
    Journal of evolutionary economics 3 (1993), S. 89-107 
    Details
    ISSN: 1432-1386
    Keywords: Emergence ; Organization ; Evolutionary dynamics ; Lambda calculus ; D 70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract In this and a companion paper (Lane 1993), I describe a class of models, called artificial worlds (AWs), that are designed to give insight into a process called emergent hierarchical organization (EHO). This paper introduces the ideas of EHO and AWs and discusses some of the interferential problems involved in trying to learn about EHO by constructing and studying the properties of AWs. It concludes by introducing two abstract AWs that address important general problems in EHO: the relation between structure and function, and the dynamics of evolutionary processes. The companion paper will discuss several AWs expressly designed to model particular economic phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01213828
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  • 4
    Electronic Resource
    Electronic Resource
    Artificial worlds and economics, part II (1993)
    Springer
    Journal of evolutionary economics 3 (1993), S. 177-197 
    Details
    ISSN: 1432-1386
    Keywords: Classifier systems ; Learning agents ; Artificial economy ; Coordination ; D 70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This paper continues the discussion of artificial worlds (AWs) begun in Lane (1993b). Here, the focus is on two kinds of AWs. The first, classifier systems, can be used to represent agents that are capable of generating complex behaviors in response to intermittent rewards from an “environment” of which they are a part. A collection of such agents, engaging in “economic” interactions with one another, produces another kind of AW, in which such interesting aggregate behaviors as the formation of bubbles and crashes and technical trading in an artificial “stock market”, may arise. The second kind of AW considered in this paper is artificial economies. These AWs can provide a dynamic, nonequilibrium, microfounded account of such aggregate-level or macroeconomic phenomena as stable growth paths, business cycles, and Pareto firm-size distributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200867
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  • 5
    Electronic Resource
    Electronic Resource
    Interaction of the trp repressor with trp operator DNA fragments (1993)
    Springer
    European biophysics journal 21 (1993), S. 417-424 
    Details
    ISSN: 1432-1017
    Keywords: trp repressor ; trp operator ; Circular dichroism ; Gel retardation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The interaction of the trp repressor with several trp operator DNA fragments has been examined by DNA gel retardation assays and by circular dichroism, in the absence and presence of the corepressor l-tryptophan. The holorepressor binds stoichiometrically to both the trpO and aroH operators, forming 1:1 complexes. In the presence of excess protein, additional complexes are formed with these operator fragments. The relative electrophoretic mobilities of the 1:1 complexes differ significantly for trp and aroH operators, indicating that they differ substantially in gross structure. A mutant trp operator, trpO c, has low affinity for the holorepressor, and forms only complexes with stoichiometries of 2:1 (repressor: DNA) or higher, which have a very low electrophoretic mobility. Specific binding is also accompanied by a large increase in the intensity of the near ultraviolet circular dichroism, with only a small blue shift, which is consistent with significant changes in the conformation of the DNA. Large changes in the chemical shifts of three resonances in the 31P NMR spectrum of both the trp operator and the aroH operator occur on adding repressor only in the presence of L-tryptophan, consistent with localised changes in the backbone conformation of the DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185869
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  • 6
    Electronic Resource
    Electronic Resource
    31P NMR relaxation measurements of the phosphate backbone of a double stranded hexadeoxynucleotide in solution: determination of the chemical shift anisotropy (1990)
    Springer
    European biophysics journal 18 (1990), S. 347-355 
    Details
    ISSN: 1432-1017
    Keywords: Chemical shift anisotropy ; 31P relaxation ; DNA dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The five phosphates of the deoxynucleotide d(CpGpTpApCpG)2 have been assigned by two-dimensional heteronuclear NMR spectroscopy. The chemical shift anisotropy and correlation time of each phosphate group has been determined from measurements of the spin-lattice, spin-spin relaxation rate constants and the 31P-{1H} nuclear Overhauser enhancement (NOE) at three magnetic field strengths (4.7 T, 9.4 T, and 11.75 T) and two temperatures (288 K and 298 K). As expected, the relaxation data require two mechanisms to account for the observed rate constants, i.e. dipole-dipole and chemical shift anisotropy. At 9.4 T and 11.75 T, the latter mechanism dominates the relaxation, leading to insignificant NOE intensities. The correlation time, chemical shift anisotropy and effective P-H distance were obtained from least-squares fitting to the data. Comparison of the fitted value for the correlation time with that obtained from 1H measurements shows that the molecule behaves essentially as rigid rotor on the nanosecond timescale. Large amplitude motions observed in long segments of DNA are due to bending motions that do not contribute significantly to relaxation in short oligonucleotides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196925
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  • 7
    Electronic Resource
    Electronic Resource
    Conformational properties of the —35 region of the trp promoter in solution: comparison of the wild-type sequence with an AT transversion (1993)
    Springer
    European biophysics journal 22 (1993), S. 135-143 
    Details
    ISSN: 1432-1017
    Keywords: Trp promoter ; Solution conformation ; Transversion mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The majority of the 1H NMR resonances of the protons in a tetradecamer containing the —35 region of the trp promoter d(GCTGTTGACAATTA): d(TAATTGTCAACAGC) and in the TA transversion have been assigned. The conformational properties of the nucleotides have been determined and compared in the two duplexes. Analysis of spin-spin coupling and NOES shows that all sugar puckers are in the south domain (i.e. near C2′ endo) and the glycosidic torsion angles are anti (χ≈110°). The NMR data are consistent with the duplex being in the B family of conformations. Significant differences in chemical shifts between the two molecules were observed only for nearest neighbours to the transversion site, suggesting the absence of long range conformational effects. This was confirmed by the similarity of coupling constants and NOEs. Other properties are also not greatly affected at positions more than two base pairs from the mutation site. These results are consistent with the hypothesis that unconstrained oligonucleotides are highly flexible, and can readily accommodate significant perturbations of the local structure, such as a transversion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196917
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of adinazolam and diazepam, alone and in combination with ethanol, on psychomotor and cognitive performance and on autonomic nervous system reactivity in healthy volunteers (1990)
    Springer
    European journal of clinical pharmacology 38 (1990), S. 371-377 
    Details
    ISSN: 1432-1041
    Keywords: ethanol ; adinazolam ; diazepam ; benzodiazepines ; psychomotor ; cognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Effects on psychomotor and cognitive performance of adinazolam (15 or 30 mg), alone and in combination with ethanol (0.8 g/kg), were studied in healthy male volunteers and compared to effects of 10 mg diazepam. Adinazolam 30 mg produced relatively long-lasting impairments on tests of tracking, attention, verbal and nonverbal information processing, and memory. Adinazolam 15 mg resulted in descreased visual information processing. Adinazolam decreased supine mean arterial pressure, but only the 15 mg resulted in a tendency for decreased plasma norepinephrine concentrations. After standing for 5 min, 30 mg adinazolam was associated with increased heart rate. Although ethanol consumption produced additive decrements on a continuous performance task, there was little evidence to support a synergistic effect. Adinazolam 30 mg was accompanied by increased self-reports of side effects, especially drowsiness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315578
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  • 9
    Electronic Resource
    Electronic Resource
    Menstrual cycle effects on caffeine elimination in the human female (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 543-546 
    Details
    ISSN: 1432-1041
    Keywords: Caffeine, Menstrual cycle ; pharmacokinetics, females
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Increases in the levels of sex steroids due to pregnancy or oral contraceptive steroid use are known to decrease significantly the rate at which caffeine is eliminated from the body. An investigation has now been made into whether the changes in sex steroid levels that occur during normal menstrual cycling also affect the rate of caffeine elimination, especially whether hormonal shifts in the luteal phase are associated with slower elimination of caffeine. Repeated 24-hour caffeine elimination studies were conducted during the follicular and luteal phases of the menstrual cycle in 10 healthy women. Comparisons of the follicular and luteal phases revealed that systemic clearance of caffeine was slower in the luteal phase, although the t1,2 did not differ. The slowing effect was related to the proximity to onset of menstruation and to levels of progesterone. The evidence suggests that caffeine elimination may be slowed in the late luteal phase, prior to the onset of menstruation. Such a reduction would lead to increased accumulation of caffeine with repeated self-administration during the day, but the effect may be too small to be of clinical significance in the majority of women.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02285099
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  • 10
    Electronic Resource
    Electronic Resource
    Anisotropic rotation in nucleic acid fragments: significance for determination of structures from NMR data (1990)
    Springer
    European biophysics journal 19 (1990), S. 73-78 
    Details
    ISSN: 1432-1017
    Keywords: DNA hydrodynamics ; Cross relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Proton-proton relaxation rate constants depend on the angle between the internuclear vector and the principal axis of rotation in symmetric top molecules. It is possible to determine to rotational correlation times of the equivalent ellipsoid for DNA fragments from a knowledge of the axial ratio and the cross-relaxation rate constant for the cytosine H6-H5 vectors. The cross-relaxation rate constants for the cytosine H6-H5 vectors have been measured in the 14-base-pair sequence dGCTGTTGACAATTA.dTAATTGTCAACAGC at four temperatures. The results, along with literature data for DNA fragments ranging from 6 to 20 base pairs can be accounted for by a simple hydrodynamic equation based on the formalism of Woessner (1962). The measured cross-relaxation rate constant is independent of position in the sequence and is consistent with the absence of large amplitude internal motions on the Larmor time scale. All the data can be described by a simple hydrodynamic model, which accounts for the rotational anisotropy of the DNA fragments and allows the correlation time for end-over-end tumbling to be determined if the approximate rise per base pair is known. This is the correlation time that dominates the spectral density functions for internucleotide vectors and is significantly different from that calculated for a sphere of the same hydrodynamic volume for fragments containing more than about 14 base pairs. This method therefore allows NOE intensities used for structure calculation of nucleic acids to be treated more rigorously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185089
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