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  • 1
    Electronic Resource
    Electronic Resource
    Hydrodynamic properties of a polyisoprene/polyoxyethylene block copolymer (1990)
    s.l. : American Chemical Society
    Macromolecules 23 (1990), S. 4461-4464 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00222a020
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  • 2
    Electronic Resource
    Electronic Resource
    Central melatonin receptors: Implications for a mode of action (1989)
    Springer
    Cellular and molecular life sciences 45 (1989), S. 955-965 
    Details
    ISSN: 1420-9071
    Keywords: Melatonin ; receptors ; in vitro ; autoradiography ; brain ; pituitary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The influence of melatonin on circadian and photoperiodic functions in numerous species is well documented. It is known that the effect of melatonin on circadian rhythmicity is mediated via the suprachiasmatic nucleus (SCN), the biological clock of the brain. It is not known however where the photoperiodic effects of melatonin are mediated. Evidence from brain lesioning and melatonin implant studies point to a site in or near the medial hypothalamus. In contrast to these studies, melatonin receptors have been reported in widespread areas of the brain, the pituitary and in peripheral tissues. The characteristics of the reported melatonin receptors vary widely between studies and consequently no definitive description of a physiologically relevant melatonin receptor has received universal recognition. This review marshals recent evidence for the localization and characterization of the melatonin receptor and discusses these findings in the context of the known effects of the hormone in different species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01953053
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  • 3
    Electronic Resource
    Electronic Resource
    Reproductive energetics, endocrinology and population dynamics of Nephtys caeca and N. hombergi (1985)
    Springer
    Marine biology 88 (1985), S. 235-246 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An investigation of gametogenetic cycles and spawning success in populations of Nephtys caeca and N. hombergi from the River Tyne estuary, North Shields, England, in relation to production of gonadotrophic (GH) and spawning hormones (SH) has been made, based on data collected from 1978–1984. The data show that a consistent pattern of gametogenesis and efficient spawning occurs in populations of N. caeca in north-east England, but that the reproductive cycle of N. hombergi is erratic. Premature oosorption and gametogenic failure in this latter species is associated with a low level of GH production. Following high levels of GH production, gravid females sometimes fail to spawn owing to the non-release of SH. The reproductive energetics and reproductive success of N. caeca and N. hombergi are described in relation to the observed patterns of endocrine activity and the consequent changes in population structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392586
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  • 4
    Electronic Resource
    Electronic Resource
    Use made in marine ecology of methods for estimating demographic parameters from size/frequency data (1987)
    Springer
    Marine biology 95 (1987), S. 201-208 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Macdonald and Pitcher's method of decomposing a sizefrequency histogram into cohorts (mathematical optimization of the fit of the distribution function to the histogram) has been used to estimate the composition of random samples drawn from populations with known cohort structure. The large-sample behaviour of the method is in accordance with the results of asymptotic theory. With sample sizes typical of those used in many ecological studies, good estimates often could not be obtained without imposing constraints upon the estimation procedure, even when the number of age classes in the population was known. If the number of age classes was not known, it was frequently difficult to determine from small samples. When unconstrained solutions were obtainable, confidence limits about estimates were often very wide. Our results and information in the theoretical literature indicate that if the Petersen method (whereby several modes on a size-frequency histogram are taken to represent single age classes and all age classes to be present) does not work, accurate estimates of demographic parameters are unlikely to be obtainable using more rigorous methods. In view of these difficulties, we recommend that an iptimization method, such as that described by Macdonald and Pitcher, be used to estimate demographic parameters. Standard errors of estimates should be reported. Optimization methods give an indication when the data is inadequate to obtain accurate parameter estimates, either by failing to converge or by placing large standard errors about the estimates. Graphical methods do not give a clear warning of this, and should be avoided except where the modes on the size-frequency histogram are very well separated and sample sizes are large. Often, assumptions must be made about population parameters to enable their estimation. This may involve constraining some parameters to particular values, assuming a fixed relationship between cohort mean sizes and their standard deviations, or by assuming that individuals grow according to a von Bertalanffy curve. Any such assumptions need detailed justification in each case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00409006
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  • 5
    Electronic Resource
    Electronic Resource
    Novel naphthalenic ligands with high affinity for the melatonin receptor (1992)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 35 (1992), S. 1484-1486 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00086a018
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of Earth rotation as inferred from radio interferometric, laser ranging and astrometric observations (1983)
    [s.l.] : Nature Publishing Group
    Nature 302 (1983), S. 509-511 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The VLBI data, analysed at the National Geodetic Survey (NGS), were obtained in the MERIT short campaign and from the NGS's project POLARIS3. The MERIT data, collected during two 1-week observing sessions in September and October 1980, resulted from observations of up to five antennas operating ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/302509a0
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructure of melatonin-responsive cells in the ovine pars tuberalis (1991)
    Springer
    Cell & tissue research 263 (1991), S. 529-534 
    Details
    ISSN: 1432-0878
    Keywords: Melatonin ; Pituitary gland, pars tuberalis ; Secretory cells ; Cyclic AMP ; Ultrastructure ; Cell culture ; Sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Functional receptors for melatonin have been localized and characterized on the pars tuberalis (PT) of a number of mammalian species, but the cell-type responsive to melatonin is unknown. The ultrastructure of the ovine pars tuberalis has been examined and these findings correlated with the functional response of the gland to melatonin. This study revealed that two secretory cell types predominate in the ovine PT, which differ in the abundance of dense-core granules. The most abundant of the cells are either agranular or very sparsely granulated and represent 90% of the total population, with the remaining 10% being composed of cells with abundant dense-core vesicles. Few follicular cells were observed. This ratio of secretory cell-types persisted in primary culture, with the two types non-separable by Percoll gradient centrifugation. Using forskolin, as a non-specific stimulant of adenylate cyclase, melatonin was shown to inhibit the formation of cyclic AMP by 80–90% in cells both before and after Percoll centrifugation. The results demonstrate that the agranular secretory cells of the ovine pars tuberalis are the melatonin responsive cell-type of this gland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327285
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  • 8
    Electronic Resource
    Electronic Resource
    Electrochemical gradients acrossLocusta Malpighian tubules (1983)
    Springer
    Journal of comparative physiology 151 (1983), S. 175-183 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The use of conventional microelectrodes has revealed that the basal membrane potential (Emb) and the transepithelial potential (Tm) inLocusta Malpighian tubules are −39.4 mV and +4.4 mV respectively. No change in Emb was noted after stimulation by diuretic hormone (DH) or cAMP (5 mM), suggesting electroneutral coupling of ions entering the cell. Intracellular concentrations of potassium and chloride measured by ion selective microelectrodes (ISMs) are 95 mM and 51 mM respectively, and intraluminal potassium measured by direct impalement using ISMs is 139 mM. Luminal sodium and chloride concentrations, measured indirectly, by ISMs in the secreted fluid, are 20 mM and 203 mM respectively in unstimulated tubules. Using the data for the electrical and chemical gradients it has been possible to speculate how the different ions enter and exitLocusta tubule cells. A hypothetical model has been formulated in which it is suggested that K+ and Na+ can enter across the basal membrane passively but require an energy dependent mechanism to exit across the apical membrane. Conversely Cl− must enter by an energy dependent mechanism but can exit down a favourable electrical gradient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689916
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  • 9
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    Decoding photoperiodic time through Per1 and ICER gene amplitude (1999)
    National Academy of Sciences
    Details
    Publication Date: 1999-08-17
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Hydrodynamic properties of a polyisoprene/polyoxyethylene block copolymer (1990)
    American Chemical Society
    Details
    Publication Date: 1990-10-01
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
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