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  • 1995-1999  (2)
  • 1998  (2)
  • Occupational Health and Environmental Toxicology  (1)
  • Synapse  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 182 (1998), S. 501-507 
    ISSN: 1432-1351
    Keywords: Key words Photoinactivation ; Glial cells ; Motor pattern ; Synapse ; Invertebrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The activity of heart interneurons (HN cells) and heart motor neurons in the central nervous system of the medicinal leech was recorded intracellularly from their cell bodies in the third and fourth segmental ganglion (G3 and G4, respectively). Reciprocal inhibitory synaptic transmission between HN cells in the G3 was blocked by photoinactivation of neuropil glial cells in the same ganglion. The block disrupted the alternating rhythmic spike activity of HN cells in the G3 in isolated G3s but not in chains of G3 and G4. In the latter case, the rhythmic spike pattern of HN cells in the G3 appears to originate in the G4 because, for example, severing one connective between the G3 and G4 silenced the ipsilateral heart interneuron in the G3, whereas its contralateral homologue remained rhythmically active. Simultaneous recordings from HN cells in the G3 and G4 suggest that the latter may serve to coordinate the rhythmic activity of HN cells in the G3, when synaptic interaction between HN cells in the G3 is blocked. This study reveals a considerable capacity of the neural network controlling the heart beat to compensate for the impairment of synapses within one ganglion.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0197-8462
    Keywords: electromagnetic field ; myositis ossificans ; osteoblastic cells ; in vitro ; 3-D cell culture ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Human osteoblastic cells were grown in a three-dimensional (3-D) cell culture model and used to test the effects of a 20 Hz sinusoidal electromagnetic field (EMF; 6 mT and 113 mV/cm max) on collagen type I mRNA expression and extracellular matrix formation in comparison with the effects of growth factors. The cells were isolated from trabecular bone of a healthy individual (HO-197) and from a patient presenting with myositis ossificans (MO-192) and grown in a collagenous sponge-like substrate. Maximal enhancement of collagen type I expression after EMF treatment was 3.7-fold in HO-197 cells and 5.4-fold in MO-192 cells. Similar enhancement was found after transforming growth factor-β (TGF-β) and insulin-like growth factor-I (IGF-I) treatment. Combined treatment of the cells with EMF and the two growth factors TGF-β and IGF-I did not act synergistically. MO-192 cells produced an osteoblast-characteristic extracellular matrix containing collagen type I, alkaline phosphatase, and osteocalcin, together with collagen type III, TP-1, and TP-3, two epitopes of an osteoblastic differentiation marker. The data suggest that the effects of EMFs on osteoblastic differentiation are comparable to those of TGF-β and IGF-I. We conclude that EMF effects in the treatment of skeletal disorders and in orthopedic adjuvant therapy are mediated via enhancement of collagen type I mRNA expression, which may lead to extensive extracellular matrix synthesis. Bioelectromagnetics 19:222-231, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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