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  • 1
    Electronic Resource
    Electronic Resource
    Differential Seasonal Regulation of Melatonin Receptor Density in the Pars Tuberalis and the Suprachiasmatic Nuclei: A Study in the Hedgehog (Erinaceus europaeus, L.) (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 5 (1993), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Using quantitative autoradiography, we have studied the seasonal changes of high affinity melatonin receptor density in both the SCN and PT of the hedgehog, a seasonal breeder and an hibernator. Animals in 3 different physiological states were studied: sexually active animals, and sexually inactive animals during the hibernation period, being then either euthermic or hypothermic. In sexually active animals, Bmaax were 75.8 ± 7.1 fmol/mg protein in PT and 9.1 ± 0.5 fmol/mg protein in SCN; and Kd values were: 94 ± 22 pM in the PT and 101 ± 15 pM in the SCN. This specific binding was strongly decreased in the PT of sexually inactive animals. Moreover, this decrease was significantly stronger in hypothermic than in euthermic hedgehogs. Saturation studies and Scatchard analysis revealed that the observed decrease in the PT resulted from change in the Bmax but not in the Kd, Bmax values being respectively 56.4 ± 5.9 and 29.5 ± 1.9 fmol/mg protein in euthermic and hypothermic sexually at rest animals. In none of the different physiological states, did the density of melatonin receptors of the SCN show any changes, Bmaax values being respectively 9.8 ± 0.5 and 9.8 ± 0.4 fmol/mg protein in euthermic and hypothermic sexually at rest animals. This shows for the first time a tissue-specific regulation of melatonin receptor density occurring in the PT but not in the SCN. Furthermore, this decrease of binding in the PT is correlated with both sexual inactivity and hibernation period. This strongly suggests that the mediation of the photoperiodic effect on seasonal functions like seasonal hypothermia and reproduction involves an effect of melatonin on the PT rather than on the SCN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1993.tb00540.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Constant Light, Pinealectomy and Guanosine Triphosphate Gamma-S on the Density of Melatonin Receptors in the Rat Suprachiasmatic Nucleus: A Possible Implication of Melatonin Action (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 4 (1992), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We report here the effects of pinealectomy and exposition to constant light on the density of melatonin receptors in the suprachiasmatic nuclei of the rat using quantitative autoradiography. The Bmaxvalues were significantly increased when the animals were maintained in constant light for 3 days (8.22 ± 0.95 fmol/mg protein versus 4.55±0.14 fmol/mg protein in control group, 12 h light/12 h dark cycle (12L/12D), n = 6). A similar increase was also observed in rats pinealectomized 3 days before sacrifice and then maintained either under 12L/12D (Bmax7.56±0.80 fmol/mg protein) or in constant light (Bmax7.85±1.02 fmol/mg protein), while Kdvalues failed to show any variations after constant light and/or pinealectomy.The effect of GTPγS on the density of rnelatonin binding sites was also investigated in control animals and after 3 days of constant light. In 12L/12D animals, the Bmax shifted from 5.94 ± 0.14 fmol/mg protein in the absence of GTPγS to 3.97±0.22 fmol/ mg protein in the presence of 50μiM GTPγS. In animals maintained for 3 days in constant light, a similar decrease in the Bmax value was observed (8.95 ± 0.25 fmol/mg protein in absence and 5.95 ± 0.22 fmol/mg protein in presence of 50 μ GTPγS). In both cases, Kd values were not affected by GTPγS.Pinealectomy and constant light exposition are known to induce a suppression of the nocturnal peak of plasma rnelatonin and to keep plasma rnelatonin concentrations at a very low level. These results could suggest a regulatory effect of rnelatonin on the density of its own receptors which are shown here to be also coupled with a G-protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1992.tb00193.x
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  • 3
    Electronic Resource
    Electronic Resource
    Differential regulation of melatonin receptors by short- versus long-term pinealectomy in the rat suprachiasmatic nuclei and pars tuberalis (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 16 (1994), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Gauer F, Masson-Pévet M, Pévet P. Differential regulation of melatonin receptors by short- versus long-term pinealectomy in the rat suprachiasmatic nuclei and pars tuberalis. J. Pineal Res. 1994: 16: 73–76.〈section xml:id="abs1-1"〉〈title type="main"〉AbstractWe have investigated the effects of short- and long-term pinealectomy on the density of melatonin receptors in both the suprachiasmatic nuclei (SCN) and pars tubercles (PT) of the rat. Short-term pinealectomy (conducted 3-5 days before sacrifice) induced a significant increase in the density of melatonin receptors in both structures. This increase can be interpreted as an up-regulation of melatonin receptors following the absence of plasma melanoma. In contrast, 7 days after pinelectomy, the receptor density began to decrease, reaching a low point 1. 5 months after pinealectomy. At this time, the decrease represents a 40-45% reduction in binding sites as compared with values measured 3–5 days after pinealectomy. This slow decrease could be related to a slowdown of melatonin receptor synthesis. These results suggest that emblazoning has a stimulatory effect on its own receptor synthesis. However, at 1. 5 months after pinealectomy a novel equilibrium between synthesis and hydrolysis seems to be reached. Melanoma does not appear to be indispensable for the synthesis of its receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1994.tb00085.x
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of niobium additions on high-temperature-oxidation behavior of Ti3Al alloys and coatings (1994)
    Springer
    Oxidation of metals 42 (1994), S. 49-74 
    Details
    ISSN: 1573-4889
    Keywords: titanium aluminides ; Ti3Al ; oxidation resistance ; sputtered coatings ; oxidation mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this study, the oxidation properties of Ti3Al+Nb bulk alloys, as well as IMI 829 alloy, coated with a Ti3Al+Nb layer, have been considered. Model alloys have been prepared, with 5–25 at.% niobium contents; 50-μm-thick Ti3Al+10 at.% Nb coatings have also been deposited on IMI 829 by triode sputtering. Bulk alloys and coated substrates have been exposed to cyclic and isothermal oxidation in air between 700 and 800°C. Niobium additions generally caused the oxidation rate of Ti3Al to decrease significantly. In all cases rutile is the main oxide formed. It is believed that the ability of niobium to dissolve in the rutile lattice, and therefore to lower the oxygen diffusion rate through the oxide layer, is a contribution to the observed oxidation resistance enhancement. The formation of niobium oxide has also been envisaged for this matter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01061924
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  • 5
    Electronic Resource
    Electronic Resource
    Demonstration of melatonin-binding sites in cyclohexylamine-formaldehyde-fixed brain tissues (1993)
    Springer
    Cell & tissue research 274 (1993), S. 207-209 
    Details
    ISSN: 1432-0878
    Keywords: Melatonin receptors ; Suprachiasmatic nucleus ; Pars tuberalis ; Cyclohexylamine formaldehyde fixation ; Rat (Wistar) ; Syrian hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This study shows for the first time that perfusion of rat or hamster brain with a cyclohexylamine-paraformaldehyde mixture makes possible the observation by autoradiography of melatonin binding sites in structurally well-preserved fixed tissues. This result is a first step in the identification of melatonin-receptor-containing cell types by cytoautoradiography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328002
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  • 6
    Electronic Resource
    Electronic Resource
    Seasonal regulation of melatonin receptors in rodent pars tuberalis: correlation with reproductive state (1994)
    Springer
    Journal of neural transmission 96 (1994), S. 187-195 
    Details
    ISSN: 1435-1463
    Keywords: Melatonin receptors ; seasonal variation ; photoperiod ; pars tuberalis ; reproductive state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Using quantitative autoradiography, we have studied the relationship between melatonin receptor density in the pars tuberalis (PT) and photoperiodic changes in sexual activity in a photoperiodic (Syrian hamster), and a non photoperiodic (rat) rodent. Syrian hamsters exposed to short photoperiod (SP) for 13 weeks or kept in long photoperiod (LP) with daily melatonin injections for 8 weeks, had both gonadal regression and a significant decrease in 2-125I-melatonin binding site density in the PT when compared to controls. In contrast, when the animals were sexually active, photorefractory Syrian hamsters exposed to SP for 27 weeks, or rats kept for 13 weeks in SP, the PT melatonin receptor density was similar to that of control animals kept in LP. These results show clearly that a correlation exists between gonadal status and density of melatonin receptors in the PT and suggest that the PT could be the site where melatonin mediates its effects on seasonal function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294786
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  • 7
    Electronic Resource
    Electronic Resource
    Sexual cycle ofBabesia divergens confirmed by DNA measurements (1990)
    Springer
    Parasitology research 76 (1990), S. 199-206 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The DNA content of the developmental stages within the life cycle ofBabesia divergens was measured by means of fluorescence microscopy using the DNA-specific bisbenzimide Hoechst 33258. By comparing the mean relative fluorescence intensities, the assumption of sexual reproduction in the gut of the tick vector (Ixodes ricinus) was confirmed. However, no proof of a pre- or postzygotic meiosis was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00930815
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