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  • COMMUNICATIONS AND RADAR  (3)
  • Corticosteroid  (3)
  • 1
    ISSN: 1432-0878
    Keywords: Adrenal gland ; Cell culture ; ACTH ; Ageing ; Corticosteroid ; Cytoskeleton ; Domestic mallard, embryos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphological and functional changes associated with ageing were studied in adrenal steroidogenic cells derived from duck embryos. Cells grown for not more than three days had structural characteristics similar to their counterparts in vivo; they contained numerous lipid droplets and mitochondria, an abundant smooth edoplasmic reticulum, an even network of microtubules, and microfilaments that formed extensive and elaborate systems of parallel stress fibers. After the 3rd day of growth in culture, many of the cells started to decrease in size and become elongated; the older cells showed less well-defined actin filaments and contained elongated mitochondria, fewer lipid droplets, less smooth endoplasmic reticulum, and swollen cisternae of rough endoplasmic reticulum. The proliferative capacity of the cells was the same when they were cultured in either the presence or the absence of 1–24 ACTH. After the first day of growth in culture, the steroidogenic capacity of the cells declined and the addition of 1–24 ACTH to the growth medium did not prevent changes in their structure and function. The decline in steroidogenic capacity occurred both in terms of the amount of hormone released into the culture medium and in the ability of the cells to respond when incubated in buffer containing 1–24 ACTH. Since the basal unstimulated rates of corticosteroid production also declined as the cells aged, it is probable that the steroidogenic deficiency occurs at a site distal to the corticotropin receptor; this is also consistent with the ultrastructural observations that suggest a relationship between the morphological changes and the decline in steroidogenic capacity as the cells age.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 258 (1989), S. 593-601 
    ISSN: 1432-0878
    Keywords: Adrenal gland ; Corticosteroid ; Steroidogenesis ; Embryogenesis ; ACTH ; Mallard duckling, Anas platyrhynchos (Aves, Anatiformes)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The differentiating nephrotome in the 10-day-old mallard duck embryo is able to synthesize corticosterone, aldosterone and deoxycorticosterone even though an adrenal anlage cannot be identified histologically until the 12th day of incubation. At this time, sudanophilic cells containing much smooth endoplasmic reticulum and numerous mitochondria with tubular cristae are located adjacent to the developing mesonephros. Chromaffm cells appear in this region on about the 14th day of embryogenesis. A discrete glandular structure containing measurable quantities of corticosteroids can be identified on the 15th day, and during the next 2 days the tissue becomes encapsulated. Concomitantly, the ACTH-inducible rates of corticosteroid hormone synthesis increase several fold. The corticotropic responsiveness of the developing adrenal steroidogenic tissue increases progressively during the remainder of embryogenesis.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0878
    Keywords: ACTH ; Adrenal gland ; Cell culture ; Corticosteroid ; Steroidogenesis ; Mallard duckling (Anas platyrhynchos)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Primary cell cultures were prepared from the adrenal glands of one-day-old mallard ducklings (Anas platyrhynchos). The cells attached equally well to uncoated plastic and glass surfaces and on surfaces that had been coated with collagen. The phase of logarithmic growth occurred between the second and the fourth day, and the cells became confluent between the fifth and the sixth day. Staining with Sudan black B and toluidine blue and viewing fixed preparations by transmission electron microscopy indicated that the cultures consisted mostly of steroidogenic cells. A smaller population of chromaffin cells was also present. Scanning electron microscopy showed that most of the cells had long filopodia, and some cells had numerous surface blebs that were interpreted as exocytotic vesicles. When incubated in Krebs-Henseleit buffer containing 1–24 ACTH the cultured cells released three corticosteroids, namely, corticosterone, aldosterone and deoxycorticosterone. These responses occurred within 15 min of exposure to medium containing 1–24 ACTH and continued throughout a 60-min period of continuous stimulation. The minimally effective concentration of 1–24 ACTH was 0.078 ng per ml (0.0234 nM) and, as the concentration was increased up to 10 ng per ml (2.99 nM), the total output of each hormone during the 60-min incubation period increased significantly according to the following semi-logarithmic relationship: Y=a+b log X, where Y=the total output of hormone, X=the concentration of 1–24 ACTH in the medium, and a=the total output of hormone when the medium contained 1.0 ng of 1–24 ACTH per ml. The total outputs of each hormone in the presence of a maximally effective concentration of 1–24 ACTH, however, were low compared to the responses of similarly stimulated tissue slices taken from the neonatal duckling. It is concluded that most of the cells comprising the confluent cultures were derived from steroidogenic cells in the neonatal adrenal. These cells appeared to retain corticotropin receptors during the course of developing into confluent monolayers, but their diminished steroidogenic capacity to respond when stimulated maximally suggests that some generational changes may have occurred.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2019-07-13
    Description: To guard against severe rain losses at 30 and 20 GHz, techniques are being developed which provide the high antenna gain needed to increase communications margins and frequency reuse capability through beam isolation, while providing complete coverage of the U.S. Effective bandwidths from a single satellite location may then reach tens of gigahertz, with capacity tailored to match nonuniform geographic demand patterns. Satellite onboard processing which includes forward-error-correction and the routing of channels to terminals will reduce scanning antenna requirements and increase rain margins, through the adaptive use of system margins to support those terminals experiencing rain. These antenna and onboard processing techniques are adaptable to C-band and Ku-band, in addition to Ka-band.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: ITC/USA/''80; Oct 14, 1980 - Oct 16, 1980; San Diego, CA
    Format: text
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  • 5
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    Unknown
    In:  Other Sources
    Publication Date: 2019-07-13
    Description: The satellite communication system described provides communications for very small and very large (trunking) users. Independent combinations of FDMA and TDMA are used in the uplink and downlink designs to minimize terminal costs. Signal routing for small users is accomplished by a digital store-and-forward technique which greatly simplifies the terminal receiver, compared to satellite-switched TDMA. Different processing techniques are used for very high data rate users, but complete interconnectivity between all users is maintained. This avoids double-hop routing with excessive transmission delays.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AIAA PAPER 80-0583 , Communications Satellite Systems Conference; Apr 20, 1980 - Apr 24, 1980; Orlando, FL
    Format: text
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  • 6
    Publication Date: 2019-07-13
    Description: A domestic satellite system architecture that can efficiently and economically accommodate a wide variety of disparate user classes is described and a baseline system configuration identified. With such a technique, both the efficiency of TDMA operation and the operational terminal flexibility of FDMA can be simultaneously achieved.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AIAA PAPER 80-0494 , Communications Satellite Systems Conference; Apr 20, 1980 - Apr 24, 1980; Orlando, FL
    Format: text
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