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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 183 (1998), S. 193-202 
    ISSN: 1432-1351
    Keywords: Key words Fura-2 ; Fluorescence ; Limulus ventral photoreceptors ; Mn2+ ; Calcium influx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In contrast to insect species, light-activated influx of divalent ions into Limulus ventral photoreceptors has proven difficult to demonstrate. We used the quench of the fluorescent indicator dye, fura-2, to measure Mn2+ influx. Limulus ventral photoreceptors were injected with fura-2 and excited at 360 nm. When the photoreceptors were bathed in 1 mmol · l−1 Mn2+, an approximately 1% per 10 s decline in the fura-2 fluorescence during intervals between 50-ms flashes was taken as a measure of Mn2+ entry in darkness. Fluorescence decline during 10-s flashes was used to monitor Mn2+ entry during the photoresponse. During the 10-s flashes we observed a small rapid decline of the fura-2 fluorescence even in the absence of Mn2+. This reflected a contamination of the fluorescence signal arising from light-induced release of intracellular calcium stores. A subsequent slower decline in fluorescence during the 10-s flash, amounting to approximately 9% per 10 s, was only observed in the presence of extracellular Mn2+ and was attributed to Mn2+ influx. This light-activated influx was not through voltage-gated calcium channels since it persisted under voltage clamp, was not stimulated by depolarizing current injections, nor blocked by NiCl2. Depletion of internal calcium stores by cyclopiazonic acid treatment did not accelerate Mn2+ influx.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 124 (1985), S. 439-445 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Extracts of term human placenta were tested for enhancement of proliferative growth of primary cultures of human keratinocytes. Saline extracts or supernatants from homogenates were dialyzed extensively, lyophilized, and tested in subcultures of keratinocytes in MCDB 153 medium with 0.1 mM Ca++ containing only defined supplements (insulin, hydrocortisone, transferrin, ethanolamine, phosphoethanolamine). Cells plated in the absence of EGF at moderately high densities (1000-3000 cells per cm2) formed colonies and grew in the presence of placental extract at 25-500 μg/ml. Extracts of cord serum or maternal serum were inactive, suggesting that the activity is derived from placental tissue. The activity is not EGF, since the activity in the placental extract, unlike EGF, did not promote growth at low cell density, was synergistic with EGF under some conditions, and did not produce changes in colonial morphology which occurred in the presence of EGF. Unlike keratinocyte growth-promoting activity in bovine hypothalamic extract, the activity is nondialyzable and is destroyed at 100°C. Placental extract could not replace any of the defined components of the medium and is therefore distinct from them. The presence of activity in the placenta with distinctive properties suggests that this is a previously undescribed material with growth-promoting properties for epithelium.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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