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  • 1
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    Tyrosyl phosphorylation and activation of MAP kinases by p56lck (1992)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1992-02-14
    Description: T cell signaling via the CD4 surface antigen is mediated by the associated tyrosyl protein kinase p56lck. The 42-kilodalton mitogen-activated protein (MAP) kinase (p42mapk) was tyrosyl-phosphorylated and activated after treatment of the murine T lymphoma cell line 171CD4+, which expresses CD4, with antibody to CD3. Treatment of the CD4-deficient cell line 171 with the same antibody did not result in phosphorylation or activation of p42mapk. Purified p56lck both tyrosyl-phosphorylated and stimulated the seryl-threonyl phosphotransferase activity of purified p44mpk, a MAP kinase isoform from sea star oocytes. A synthetic peptide modeled after the putative regulatory phosphorylation site in murine p42mapk (Tyr185) was phosphorylated by p56lck with a similar Vmax, but a fivefold lower Michaelis constant (Km) than a peptide containing the Tyr394 autophosphorylation site from p56lck. MAP kinases may participate in protein kinase cascades that link Src family protein-tyrosyl kinases to seryl-threonyl kinases such as those encoded by rsk and raf, which are putative substrates of MAP kinases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ettehadieh, E -- Sanghera, J S -- Pelech, S L -- Hess-Bienz, D -- Watts, J -- Shastri, N -- Aebersold, R -- R126604/PHS HHS/ -- New York, N.Y. -- Science. 1992 Feb 14;255(5046):853-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biomedical Research Centre, University of British Columbia, Vancouver, Canada.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/1311128" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Antigens, CD3 ; Antigens, Differentiation, T-Lymphocyte/physiology ; Calcium-Calmodulin-Dependent Protein Kinases ; Cell Line ; Glycogen Synthase Kinase 3 ; In Vitro Techniques ; Lymphocyte Specific Protein Tyrosine Kinase p56(lck) ; Lymphoma, T-Cell ; Mice ; Molecular Sequence Data ; Oncogene Proteins, Viral/*physiology ; Phosphorylation ; Protein Kinases/*physiology ; Protein-Tyrosine Kinases/*physiology ; Receptors, Antigen, T-Cell/physiology ; Signal Transduction/*physiology ; T-Lymphocytes/physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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    PAPER CURRENT
  • 2
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    Modelling the near-Earth space environment using LDEF data (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: Near-Earth space is a dynamic environment, that is currently not well understood. In an effort to better characterize the near-Earth space environment, this study compares the results of actual impact crater measurement data and the Space Environment (SPENV) Program developed in-house at POD, to theoretical models established by Kessler (NASA TM-100471, 1987) and Cour-Palais (NASA SP-8013, 1969). With the continuing escalation of debris there will exist a definite hazard to unmanned satellites as well as manned operations. Since the smaller non-trackable debris has the highest impact rate, it is clearly necessary to establish the true debris environment for all particle sizes. Proper comprehension of the near-Earth space environment and its origin will permit improvement in spacecraft design and mission planning, thereby reducing potential disasters and extreme costs. Results of this study directly relate to the survivability of future spacecraft and satellites that are to travel through and/or reside in low Earth orbit (LEO). More specifically, these data are being used to: (1) characterize the effects of the LEO micrometeoroid an debris environment on satellite designs and components; (2) update the current theoretical micrometeoroid and debris models for LEO; (3) help assess the survivability of spacecraft and satellites that must travel through or reside in LEO, and the probability of their collision with already resident debris; and (4) help define and evaluate future debris mitigation and disposal methods. Combined model predictions match relatively well with the LDEF data for impact craters larger than approximately 0.05 cm, diameter; however, for smaller impact craters, the combined predictions diverge and do not reflect the sporadic clouds identified by the Interplanetary Dust Experiment (IDE) aboard LDEF. The divergences cannot currently be explained by the authors or model developers. The mean flux of small craters (approximately 0.05 cm diameter) is overpredicted by Kessler and underpredicted by Cour-Palais. This divergence may be a result of beta-meteoroid fluxes, elliptical orbits or a combination of the two. The results of this study illustrate the definite need for more intensive study of the near-Earth space environment, particularly the small particle regime, as it is the most degrading to spacecraft in LEO.
    Keywords: GEOPHYSICS
    Type: NASA. Langley Research Center, Second LDEF Post-Retrieval Symposium Abstracts; p 54
    Format: text
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    NASA TECHNICAL REPORTS
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