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  • tau  (3)
  • Euryhalinity  (2)
  • Springer  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Life history implications of a tagging study of the largetooth sawfish, Pristis perotteti, in the Lake Nicaragua-Río San Juan system (1982)
    Springer
    Environmental biology of fishes 7 (1982), S. 207-228 
    Details
    ISSN: 1573-5133
    Keywords: Batoids ; Chondrichthyes ; Costa Rica ; Elasmobranchs ; Euryhalinity ; Freshwater adaptation ; Growth rate ; Isolation of population ; Nicaragua
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Of a total of 377 Pristis perotteti tagged in the Lake Nicaragua-Río San Juan System, 214 (56.8% were recovered. Eighty were recovered at the original tagging site; four moved downstream the full length of the river; and 127 tagged at the source of the river were recovered in all parts of the lake. Only one was recovered in a different river system, 58 km down the coast from the main mouth of the Río San Juan. A life span of 30 years is suggested, with rapid growth (30–40 cm per year) in the first three years, slowing to about 4 or 5 cm per year in the later years of life. Maximum sizes collected were 384 cm for males, 429 cm for females, smaller than maximum lengths reported elsewhere. The lake sawfish are not physically landlocked, but individuals remain in fresh water for very long periods; parturition takes place in fresh water; all sizes are found in the lake; and it appears that this stock finds all of its ecological needs met in the lake. Individuals may spend all of their lives in fresh water, although, as a species, P. perotteti has not completely abandoned the sea, since some are known to occur in salt water. The Lake Nicaragua-Río San Juan sawfish are a discrete stock, with only limited gene flow with neighboring stocks. P. perotteti is farther along in its adaptation to fresh water, in being able both to osmoregulate and reproduce there, than other known euryhaline elasmobranchs, except for the African stingray, Dasyatis garouaensis, of the Niger-Benue System, and the completely adapted South American freshwater rays (family Potamotrygonidae).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002497
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  • 2
    Electronic Resource
    Electronic Resource
    The bull shark (Carcharhinus leucas) and largetooth sash (Pristis perotteti) in Lake Bayano, a tropical man-made impoundment in Panama (1982)
    Springer
    Environmental biology of fishes 7 (1982), S. 341-347 
    Details
    ISSN: 1573-5133
    Keywords: Elasmobranchii ; Euryhalinity ; Freshwater adaptation ; Dam lake ; Osmoregulation ; Central America
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The Río Bayano in eastern Panama is one of many tropical rivers in which bull sharks (Carcharhinus leucas) and largetooth sawfish (Pristis perotteti) have been known to occur. Since both species can osmoregulate in fresh water throughout life, theoretically, both could survive in landlocked situations for many years.P. perotteti reproduces in fresh water, butC. leucas ordinarily does not, so only the former would appear to have the potential for establishing a breeding stock in such a landlocked freshwater body. The damming of the Rio Bayano and the creation of a large impoundment in 1976 provides a test of the ability of members of both species trapped there to survive and to establish breeding stocks. In 1980 and 1981 three mature femaleC. leucas were found dead in Lake Bayano and three sub-adult femaleP. perotteti were taken by trammel net. These events confirm the ability of both to survive in fresh water for long periods, but the establishment of breeding stocks appears doubtful and the question may not be answered for many years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00005568
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  • 3
    Electronic Resource
    Electronic Resource
    Phosphorylation of Tau Alters Its Association with the Plasma Membrane (2000)
    Springer
    Cellular and molecular neurobiology 20 (2000), S. 497-508 
    Details
    ISSN: 1573-6830
    Keywords: tau ; phosphorylation ; signal transduction ; protein kinase C ; Alzheimer's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The potential functions of the microtubule-associated protein tau have been expanded by the recent demonstration of its interaction with the plasma membrane. Since the association of tau with microtubules is regulated by phosphorylation, herein we examine whether or not the association of tau with the plasma membrane is also regulated by phosphorylation. 2. A range of tau isoforms migrating from 46 to 64 kDa was associated with crude particulate fractions derived from SH-SY-5Y human neuroblastoma cells, and were retained during the initial stages of plasma membrane purification. During the extensive washing utilized in purification of the plasma membrane, portions of each of these isoforms were depleted from the resultant purified membrane. Immunoblot analysis with phospho-dependent and -independent antibodies revealed selective depletion of phospho isoforms during membrane washing. This effect was more pronounced for the slowest-migrating (64-kDa) tau isoform. 3. This putative influence of phosphorylation on the association of tau with the plasma membrane was further probed by transfection of SH-SY-5Y human neuroblastoma cells with a tau construct that could associate with the plasma membrane but not with microtubules. Treatment with phorbol ester or calcium ionophore, both of which increased phospho-tau levels within the cytosol and plasma membrane, was accompanied by the dissociation of this tau construct from the membrane. 4. These data indicate that phosphorylation regulates the association with the plasma membrane. Dissociation from the membrane by phosphorylation may place tau at risk for hyperphosphorylation and ultimate PHF formation in a manner previously considered for tau dissociated from microtubules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007075115574
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  • 4
    Electronic Resource
    Electronic Resource
    Hyperactivation of Mitogen-Activated Protein Kinase Increases Phospho-Tau Immunoreactivity Within Human Neuroblastoma: Additive and Synergistic Influence of Alteration of Additional Kinase Activities (1999)
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 249-260 
    Details
    ISSN: 1573-6830
    Keywords: MAP kinase ; tau ; protein kinase C ; wortmannin ; PD98059 ; neuroblastoma ; Alzheimer's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitogen-activated protein (MAP) kinase phosphorylates tau in cell-free analyses, but whether or not it does so within intact cells remains controversial. In the present study, microinjection of MAP kinase into SH-SY-5Y human neuroblastoma cells increased tau immunoreactivity toward the phosphodependent antibodies PHF-1 and AT-8. In contrast, treatment with a specific inhibitor of MAP kinase (PD98059) did not diminish “basal” levels of these immunoreactivities in otherwise untreated cells. These findings indicate that hyperactivation of MAP kinase increases phospho-tau levels within cells, despite that MAP kinase apparently does not substantially influence intracellular tau phosphorylation under normal conditions. These findings underscore that results obtained following inhibition of kinase activities do not necessarily provide an indication of the consequences accompanying hyperactivation of that same kinase. Several studies conducted in cell-free systems indicate that exposure of tau to multiple kinases can have synergistic effects on the nature and extent of tau phosphorylation. We therefore examined whether or not such effects could be demonstrated within these cells. Site-specific phospho-tau immunoreactivity was increased in additive and synergistic manners by treatment of injected cells with TPA (which activates PKC), calcium ionophore (which activates calcium-dependent kinases), and wortmannin (which inhibits PIP3 kinase). Alteration in total tau levels was insufficient to account for the full extent of the increase in phospho-tau immunoreactivity. These additional results indicate that multiple kinase activities modulate the influence of MAP kinase on tau within intact cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006981228331
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  • 5
    Electronic Resource
    Electronic Resource
    The Order of Exposure of Tau to Signal Transduction Kinases Alters the Generation of “AD-Like” Phosphoepitopes (1999)
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 223-233 
    Details
    ISSN: 1573-6830
    Keywords: tau ; kinases ; signal transduction ; Alzheimer's disease ; phosphorylation ; paired helical filaments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The individual and sequential influence of protein kinase C (PKC), protein kinase A (PKA) and mitogen-activated protein kinase (MAP kinase) on human brain tau was examined. 2. A range of PKC concentrations generated certain phosphoepitopes common with paired helical filaments. These epitopes were masked by higher PKC concentrations, suggesting the presence of multiple tau phosphorylation sites for which PKC exhibited differing affinities and/or conformational alterations in tau induced by sequential PKC-mediated phosphorylation. 3. Prior phosphorylation by PKC enhanced the nature and extent of AD-like tau antigenicity generated by subsequent incubation with MAP kinase yet inhibited that generated by subsequent incubation with PKA. 4. Dephosphorylation of tau prior to incubation with kinases significantly altered the influence of individual and multiple kinase incubation on tau antigenicity in a site-specific manner, indicating that prior in situ phosphorylation events markedly influenced subsequent cell-free phosphorylation. 5. In addition to considerations of the potential impact of tau phosphorylation by individual kinases, these findings extend previous studies which indicate that tau antigenicity, and, presumably, its behavior in situ, is influenced by the sequential and convergent influences of multiple kinases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006977127422
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