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  • 1
    ISSN: 1432-0533
    Keywords: Astrocytes ; Gliosis ; Extracellular ATP Glial fibrillary acidic protein ; Stellation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A number of factors appear to be involved in the proliferative and hypertrophic processes which characterize reactive astrocytosis. We have investigated the possibility that ATP, an agent that is released by injured cells following tissue destruction, may be one such factor. For this purpose, we utilized primary cultures of astrocytes derived from cerebral cortices of neonatal rats to study the effect of extracellular ATP on properties associated with astrògliosis. Light microscopic studies disclosed marked stellation of astrocytes after 30–60 min of exposure to 100 μM-1 mM ATP. In addition, the content of the astrocyte-specific intermediate filament, glial fibrillary acidic protein (GFAP), was increased 35–40% following 60-min exposure to ATP; this effect persisted for 1–3 days of exposure to 100 μM ATP. [3H]Thymidine incorportion increased progressively from 1–3 days; a 3.6-fold increase in DNA synthesis was observed following 3 days of exposure to 1 mM ATP, suggesting stimulation of cellular proliferation. These findings show that high micromolar to low millimolar concentrations of extracellular ATP reproduce several features associated with reactive gliosis and suggest that extracellular ATP may be involved in the activation of astrocytes following CNS injury.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-6903
    Keywords: myo-Inositol ; astrocytes ; osmolality ; deprivation ; kinetic parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract myo-Inositol uptake measured in primary astrocyte cultures was saturable in the presence of Na+ with a Km of 13–18 μM and a Vmax of 9.4 nmoles/mg protein/hour in myo-inositol-fed cells, indicating a high affinity transport system. In myo-inositol-deprived cells, Km was about 53 μM with a Vmax of 13.2 nmoles/mg protein/hour. Decreasing osmolality decreased the Vmax to about 1.9 nmoles/mg protein/hour whereas increasing osmolality increased Vmax about 5-fold, while Kms were essentially unchanged in myo-inositol fed cells. In cells deprived of myo-inositol, Vmax decreased in hypotonic medium and increased in hypertonic medium almost 10-fold, but with more than a doubling of the Km regardless of the osmolality. Glucose (25 mM) inhibited myo-inositol uptake 51% whereas the other hexoses used inhibited uptake much less. Our findings indicate that myo-inositol uptake in astrocytes occurs through an efficient carrier-mediated Na+-dependent co-transport system that is different from that of glucose and its kinetic properties are affected by myo-inositol availability and osmotic stress.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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