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  • Key words: Prostaglandin E2— Prostaglandin E receptor — MC3T3-E1 cells — Osteoblast — Prostaglandin G/H synthase-2.  (1)
  • Ventromedial nucleus  (1)
  • 1
    ISSN: 1432-0827
    Keywords: Key words: Prostaglandin E2— Prostaglandin E receptor — MC3T3-E1 cells — Osteoblast — Prostaglandin G/H synthase-2.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Prostaglandin E2 (PGE2) is known to autoamplify its production in the osteoblasts through the induction of prostaglandin G/H synthase-2 (PGHS-2), which is the inducible form of the rate-limiting enzyme in PG synthesis, PGHS. To elucidate the cellular mechanism mediating this process, we have employed the PGE2 analogs, which are specific agonists for four subtypes of PGE receptor, and studied the potency of these analogs to induce PGHS-2 mRNA in mouse osteoblastic MC3T3-E1 cells. The induction was mainly observed by 17-phenyl-ω-trinor PGE2 (EP1 agonist) and sulprostone (EP3/EP1 agonist), but not by butaprost (EP2 agonist) or 11-deoxy PGE1 (EP4/EP2 agonist). Since EP3 subtype was undetectable in MC3T3-E1 cells, these data indicate that PGHS-2 mRNA induction is mediated through EP1 subtype of PGE receptor in MC3T3-E1 cells. PGE2 production determined by radioimmunoassay was also increased by 17-phenyl-ω-trinor PGE2 and sulprostone. The autoamplification of PGE2 production is considered to be important in elongating the otherwise short-lived PGE2 action in certain physiological conditions such as mechanical stress and fracture healing, as well as the pathological inflammatory bone loss. The observations in the present study provide us with the better understanding of these processes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 46 (1982), S. 292-300 
    ISSN: 1432-1106
    Keywords: Ventromedial nucleus ; Hypothalamus ; Antidromic activation ; Central gray ; Midbrain ; Amygdala
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In female rats anesthetized with urethane, 151 neurons in and around the ventromedial nucleus of the hypothalamus were identified by antidromic activation as having axonal projection to the mesencephalic central gray at the midcollicular level. Identified neurons were most numerous in the rostral part and at the borders of the nucleus. Antidromic spike latencies, constant for a given cell to stimulation with fixed intensity at a low repetition rate, had a wide range across cells (1.4–41.5 ms). In 37 cells, gradual increases in stimulus intensity allowed sudden discrete latency decreases as large as 9.8 ms. These may reflect activation of separate axonal branches of terminal arborizations. Eleven among 43 tested cells were antidromically driven from the dorsal longitudinal fasciculus (DLF) at the diencephalic-mesencephalic junction as well as from the central gray. Latencies of DLF responses were always shorter than those from central gray. From this and collision experiments between central gray-evoked and DLF-evoked antidromic spikes, it was concluded that at least one quarter of mesencephalic projections from the ventromedial nucleus descend through DLF. The mean conduction velocity of these axons was 0.8 m/s, indicating that they belong to thin unmyelinated C-group fibers. Thirty percent of the cell population studied received excitatory input from the cortical or medial nucleus of the amygdala. Four cells were identified as having projections both to the central gray and the amygdala. Estrogen treatment of ovariectomized female rats caused no major changes in antidromic latency, absolute refractory period or resting activity of these identified hypothalamic neurons. However, the stimulation threshold for antidromic activation was significantly lower in the estrogen-treated animals. Axons to the central gray from ventromedial hypothalamic neurons provide for hypothalamic bias on brain stem reflex paths, for reproductive and other behaviors.
    Type of Medium: Electronic Resource
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