Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Stimulation of Melatonin Synthesis in Ovine Pineals In Vitro (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 50 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Static and superfused pineal slices (750 μm) have been used to study the control of melatonin synthesis by ovine pineals. Static incubates show a time-dependent accumulation of melatonin in the medium; this is significantly increased by stimulation with norepinephrine (NE) (10−5M), reaching 300% above control levels after 4 h. Perifused pineal slices show a rapid rise in melatonin release within 12–18 min in response to NE stimulation. This reaches a 3.5–4.5-fold increase in melatonin released within 30 min. Withdrawal of NE is associated with a rapid return to prestimulated levels within 12–18 min. These time-course characteristics compare favorably to those changes seen in vivo. The formation of [14C]melatonin from [14C]-tryptophan shows a linear increase with time. In the presence of NE (10−5M), the rate of synthesis is increased, albeit after an initial time lag of at least 30 min. The latter may reflect an N-acetyltransferase-independent mechanism of synthesis and release. In static incubations, propranolol (10−5M) inhibited NE-induced melatonin production by about 60%. but prazosin (10−5M) had no effect. As dibutyryl cyclic AMP (10−3M) stimulated melatonin production, it is concluded that β-receptors are of primary importance to the control of melatonin production, as in the rat. The role of α1-receptors is less clear, but the stimulatory action of phorbol 12-myristate 13-acetate on melatonin release implicates a receptor linked to phosphatidylinositol turnover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb13232.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Neuromedin U and Neuromedin U receptor-2 expression in the mouse and rat hypothalamus: effects of nutritional status (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 87 (2003), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Neuromedin U (NMU) has been associated with the regulation of food-intake and energy balance in rats. The objective of this study was to identify the sites of gene expression for NMU and the NMU receptor-2 (NMU2R) in the mouse and rat hypothalamus and ascertain the effects of nutritional status on the expression of these genes. In situ hybridization studies revealed that NMU is expressed in several regions of the mouse hypothalamus associated with the regulation of energy balance. Analysis of NMU expression in the obese ob/ob mouse revealed that NMU mRNA levels were elevated in the dorsomedial hypothalamic (DMH) nucleus of obese ob/ob mice compared to lean litter-mates. In addition, NMU mRNA levels were elevated in the DMH of mice fasted for 24 h relative to ad libitum fed controls. The pattern of expression of NMU and NMU2R were more widespread in the hypothalamus of mice than rats. These data provide the first detailed anatomical analysis of the NMU and NMU2R expression in the mouse and advance our knowledge of expression in the rat. The data from the obese rodent models supports the hypothesis that NMU is involved in the regulation of nutritional status.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2003.02079.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Production of a prolactin releasing factor by the ovine pars tuberalis (1996)
    Oxford : Blackwell Science Ltd.
    Journal of neuroendocrinology 8 (1996), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The anterior pituitary hormone prolactin is involved in the regulation of a wide variety of processes including mammary growth, lactation, reproduction and pelage growth (1). Correspondingly, in seasonal breeders, pronounced photoperiod-driven, seasonal changes occur in the levels of prolactin secretion (2). These effects are thought to be mediated by the pineal hormone melatonin, which acts as a humoral indicator of photoperiod (3). Melatonin is thought to act through hypothalamic sites to control the gonadotrophic axis (4–6), but the sites through which melatonin modulates prolactin remain to be established. One possibility is that melatonin acts at the level of the hypothalamus to modulate the release of the hypothalamic prolactin inhibitory factor, dopamine (7). However, recent evidence from hypothalamo-pituitary disconnection experiments performed in the ram suggests that the photoperiodic modulation of prolactin secretion can occur independently of the hypothalamus, presumably due to direct effects of melatonin on the anterior pituitary (8). The only identified site of melatonin receptor expression within the ovine pituitary is the pars tuberalis (PT) (9), the cells of which are almost completely non-lactotrophic (10). Thus the possibility exists that factors released by the PT regulate the activity of lactotrophs in the pars distalis (PD). We have investigated this hypothesis using a range of co-culture and medium-conditioning experiments on primary cultures of ovine PT and PD cells, and here we report that PT cells secrete an unidentified factor that is a potent stimulus of prolactin secretion by PD cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.1996.04971.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Melatonin Inhibits the Activation of Cyclic AMP-Dependent Protein Kinase in Cultured Pars Tuberalis Cells from Ovine Pituitary (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 3 (1991), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effect of melatonin upon the activation of the intracellular effector enzyme, cyclic AMP (cAMP)-dependent protein kinase (PKA), was investigated in primary cultures of ovine pars tuberalis cells. Incubation of these cells with forskolin caused a rapid and dose-dependent activation of PKA (ED50 10∼6M). When cells were incubated with forskolin and melatonin simultaneously, the activation of PKA by forskolin was dramatically inhibited. This inhibitory effect of melatonin was dose-dependent (ED50 10−10M). Furthermore, treatment with melatonin rapidly deactivated PKA in cells prestimulated with forskolin. When pars tuberalis cell extracts were incubated with 8N3-[32P]cAMP, an analogue of cAMP used for photoaffinity labelling of native PKA, specific binding was observed in three bands with Mr of 54, 52 and 48 kd, representing the regulatory subunits of PKA II (in phosphorylated and dephosphorylated forms) and PKA I, respectively. These results indicate that melatonin is a potent inhibitory regulator of cAMP-mediated signal transduction in the ovine pars tuberalis, and suggest that the cellular effects of melatonin in this tissue are mediated by the dephosphorylation of specific substrate proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1991.tb00324.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Melatonin Regulates the Phosphorylation of CREB in Ovine Pars Tuberalis (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 6 (1994), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This study investigated whether melatonin could modulate the phosphorylation of the calcium/cyclic AMP response-element binding-protein (CREB) within primary cell cultures of ovine pars tuberalis (oPT) and pars distalis (oPD). Gel shift assays confirmed the presence of nuclear factors able to alter the electrophoretic mobility of a 32P-labelled CRE oligonucleotide. Two shifted bands were observed probably due to monomer and dimer binding to the CRE. Each band was supershifted by antisera directed against both CREB and the phosphorylated form of CREB (P-CREB), consistent with a specific role of CREB proteins in transcriptional regulation. To study the physiological role of CREB, the nuclear immunoreactivity for P-CREB was followed in primary cultures of oPT given different pharmacological treatments. Cells stimulated with forskolin responded with a robust time- and dose-dependent increase in nuclear phospho-CREB immunoreactivity (P-CREB-ir), confirming that activation of this transcription factor occurred through the cyclic AMP-PKA pathway. Maximal stimulation was achieved within 15 min and persisted for up to 1 h. Treatment with melatonin alone did not alter basal P-CREB-ir levels, yet melatonin inhibited the forskolin-induced increase in P-CREB-ir in a dose-dependent manner (IC50 of between 10−10M and 10−8 M melatonin when tested against 1 μM forskolin). In contrast, in primary cultures of oPD, melatonin failed to block forskolin-stimulated increases in either the content of cyclic AMP or the intensity of nuclear P-CREB-ir, confirming that the action of melatonin upon P-CREB-ir is tissue specific. These results demonstrate that, consistent with its inhibitory effect on the activation of PKA within oPT, melatonin prevents or reverses the phosphorylation of CREB induced by activation of the cyclic AMP signal transduction pathway. Therefore melatonin has the potential to regulate gene expression in the oPT by acting upon the CREB transcription factor. However, this paper also shows that 12-0-tetradecanoylphorbol-13-acetate (TPA) which activates PKC also leads to the phosphorylation of CREB in oPT cells, suggesting the potential involvement of other signal transduction pathways in the transcriptional regulation of these cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1994.tb00615.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Melatonin Receptor Sites in the Syrian Hamster Brain and Pituitary. Localization and Characterization Using [125|]lodomelatonin (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 1 (1989), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A high-affinity, discretely localized melatonin receptor has been characterized and mapped within the brain and pituitary of the Syrian hamster using the high specific activity ligand [125|]iodomelatonin and a combination of in vitro autoradiography and membrane homogenate receptor assays. Specific binding of radioligand was found in regions of the epithalamus and hypothalamus in the brain and the pars tuberalis of the pituitary. Excitatory amino-acid lesions destroyed [125|]iodomelatonin binding within the brain, demonstrating that binding sites are located on neurons. Analysis of [125|]iodomelatonin binding to membrane homogenates of the pars tuberalis revealed a linear relationship between specific ligand binding and the amount of tissue. The time-course of specific binding at 37°C reached equilibrium after 30 min and remained stable thereafter. The addition of increasing concentrations of [125|]iodomelatonin alone and in the presence of 1 μM melatonin showed that specific binding reached equilibrium at 80 to 100 pM. Analysis of the saturation isotherm using a one-site binding model was consistent with a single receptor site with a Kd of 29.3 (±5.9 SEM) pM and Bmax of 2.54 (±0.19 SEM) fmol/mg protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1989.tb00122.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...