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  • 1
    ISSN: 1432-0827
    Keywords: Key words: Prostaglandin E2— Prostaglandin E receptor — MC3T3-E1 cells — c-fos — c-jun.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. This study examined which subtype(s) of PGE receptors is involved in the induction of c-fos and c-jun by PGE2 in MC3T3-E1 cells. We also investigated the possibility that the induction of these genes is involved in the growth and differentiation of this cell line. PGE2 dose-dependently induced c-fos and c-jun mRNA expressions in MC3T3-E1 cells. Of the PGE analogs, 17-phenyl-ω-trinor PGE2 (EP1 agonist) and sulprostone (EP1/EP3 agonist) were far more potent than butaprost (EP2 agonist) and 11-deoxy PGE1 (EP2/EP4 agonist) in inducing c-fos and c-jun mRNA expressions. Since MC3T3-E1 cells do not express the EP3 subtype, these results suggest that PGE2 induces c-fos and c-jun mRNA expressions through the EP1 subtype of its receptor. In order to study the functional relevance of these protooncogenes, we then studied the effect of inhibition of their synthesis by the use of antisense oligonucleotide. Alkaline phosphatase (ALP) suppression by 17-phenyl-ω-trinor PGE2 was reversed by antisense oligonucleotide for either c-fos or c-jun. These results suggest that PGE2, via the EP1 subtype of the PGE receptor, negatively modulates the transition from proliferation to the matrix maturation stage through the induction of c-fos and c-jun. However, antisense oligonucleotide for c-fos or c-jun did not alter the prostaglandin G/H synthase-2 mRNA expression induced by EP1. Thus, it is possible that c-fos and c-jun inductions do not account for all the EP1-mediated PGE2 actions in MC3T3-E1 cells.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Amygdala ; Estrogen ; Preoptic area ; Septum ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Electrical stimulation of the medial amygdala (AMY) elicited antidromic action potentials in neurons in the preoptic area (POA) and the lateral septum (LS) of 36 urethane-anesthetized ovariectomized female rats, which were either treated with estrogen o not treated. The extracellular potentials from the two sites showed similar characteristics, with the exception of the sensitivity to estrogen: they had latencies between 3 and 35 ms. Thresholds were as low as 100 μA. The mean relative refractory period was 2.2 ms. The peak-to-peak amplitudes of the positive-negative biphasic potential ranged from 1.0 mV to 12.0 mV. Estrogen had site-specific effects on parameters of antidromic activation in the POA. Estrogen-treated rats had a significantly higher threshold (937 vs 664 μA) and a longer refractory period (2.5 vs 2.1 ms) than the ovariectomized rats (P 〈 0.05 for each). The effects were absent in the LS. Selective cutting of the stria terminalis diminished the AMY-induced antidromic responses in the POA and LS. Electrical stimulation of the stria blocked the AMY-induced antidromic potentials by collision. Thus, estrogen-sensitive POA efferents as well as non-estrogen-sensitive LS efferents project to the AMY via the stria terminalis. Reductions in axonal excitability would inhibit neural conduction and transmission. Estrogen may therefore reduce the AMY inputs from the POA, without affecting those from the LS. Such alterations in the neural impulse flow may underlie estrogen-dependent neuroendocrine or behavioral regulation.
    Type of Medium: Electronic Resource
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