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  • General Chemistry  (12)
  • Analytical Chemistry and Spectroscopy  (4)
  • cardiomyocytes  (3)
  • tau  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Post-receptor defect accounts for phosphorylase hypersensitivity in cultured diabetic cardiomyocytes (1992)
    Springer
    Molecular and cellular biochemistry 117 (1992), S. 63-70 
    Details
    ISSN: 1573-4919
    Keywords: glycogen phosphorylase ; alloxan-diabetes ; cardiomyocytes ; G-protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The basis for the hypersensitive response of glycogen phosphorylase to epinephrine stimulation was investigated in adult rat cardiomyocytes isolated from normal and alloxan-diabetic animals. To assess potential G-protein involvement in the response, normal and diabetic derived myocytes were incubated with either cholera or pertussis toxin prior to hormonal stimulation. Pretreatment of cardiomyocytes with cholera toxin resulted in a potentiated response to epinephrine stimulation whereas pertussis toxin did not affect the activation of this signaling pathway. To determine if the enhanced response of phosphorylase activation resulted from an alteration in adenylate cyclase activation, the cells were challenged with forskolin. After 3 hr in primary culture, diabetic cardiomyocytes exhibited a hypersensitive response to forskolin stimulation relative to normal cells. However, after 24 hr in culture, both normal and diabetic myocytes responded identically to forskolin challenge. The present data suggest that a cholera toxin sensitive G-protein mediates the hypersensitive response of glycogen phosphorylase to catecholamine stimulation in diabetic cardiomyocytes and this response which is present in alloxan-diabetic cells and is induced in vitro in normal cardiomyocytes is primarily due to a defect at a post-receptor site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230411
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  • 2
    Electronic Resource
    Electronic Resource
    Transformation of adult ventricular myocytes with the temperature sensitive A58 (tsA58) mutant of the SV40 large T antigen (1994)
    Springer
    Molecular and cellular biochemistry 136 (1994), S. 29-34 
    Details
    ISSN: 1573-4919
    Keywords: cardiomyocytes ; SV40 large T antigen ; retroviral infection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Freshly isolated ventricular myocytes have been used extensively as an adult cardiac model system. Due to their inability to undergo cytokinesisin vitro and their dedifferentiated properties in long-term culture, they can not be used for extended studies. Recent reports tell of the establishment of fetal and neonatal cardiac cell lines and the development of adult cardiomyocytes from transgenic animals. A recent report by Kirshenbaum [1], is the first to demonstrate insertion of genes in to adult ventricular myocytes using viral infection. This paper discusses the infection of primary adult differentiated cardiomyocytes with the SV40 large T antigen and subsequent proliferation under temperature sensitive control. Upon further characterization, the cells could be used as a model to study muscle differentiation and repair as well as adult cardiac cell physiology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00931601
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  • 3
    Electronic Resource
    Electronic Resource
    Identification of the molecular basis for phosphorylase hypersensitivity in cultured diabetic cardiomyocytes (1995)
    Springer
    Molecular and cellular biochemistry 145 (1995), S. 131-139 
    Details
    ISSN: 1573-4919
    Keywords: glycogen phosphorylase ; alloxan-diabetes ; cardiomyocytes ; cGMP ; phosphodiesterase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The focus of this study was to identify the molecular basis for the hypersensitive response of glycogen phosphorylase activation to epinephrine stimulation in alloxan diabetic-derived cardiomyocytes. Cyclic AMP levels were found not to be significantly different between normal and diabetic-derived cells while cGMP concentrations were found consistently to be significantly lower in diabetic-derived cells than in normal cells. Treatment with cyclic GMP analogues did not affect phosphorylase activation by epinephrine in normal cardiomyocytes whereas, IBMX, a nonselective phosphodiesterase inhibitor, had a significant effect on basal and agonist-stimulated phosphorylase activity in both normal and diabetic-derived cardiomyocytes. Differences in the time course for the rate of decay of phosphorylasea from agonist-stimulated to basal levels were observed between normal and diabetic cells. After 3 h in primary culture, phosphorylasea activity returned to basal levels more quickly in normal than in diabetic-derived cells while after 24 h in culture, the time for phosphorylasea decay was not significantly different between normal and diabetic myocytes and was longer than the 3 h response. After 3 h in primary culture, no significant difference in phosphorylase kinase activity was observed between normal and diabetic-derived cells exposed to epinephrine whereas, after 24 h in culture, phosphorylase kinase activity was significantly decreased in diabetic cells under basal and agonist-stimulated conditions. These data collectively suggest that the hypersensitive response of glycogen phosphorylase to epinephrine stimulation in diabetic-derived cardiomyocytes is not due to a defect present at the level of phosphorylase kinase but may, in part, result from an alteration in cardiac phosphodiesterase activity resulting from diminished intracellular cyclic GMP concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00935485
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Adaptive, global, extended Kalman filters for training feedforward neural networks (1994)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 391-407 
    Details
    ISSN: 0886-9383
    Keywords: Neural networks ; Non-linear multivariate regression ; Pattern classification ; Kalman filter ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Finding methods for the optimization of weights in feedforward neural networks has become an ongoing developmental process in connectionist research. The current focus on finding new methods for the optimization of weights is mostly the result of the slow and unreliable convergence properties of the gradient descent optimization used in the original back-propagation algorithm. More accurate and computationally expensive second-order gradient methods have displaced earlier first-order gradient optimization of the network connection weights. The global, extended Kalman filter is among the most accurate and computationally expensive of these second-order weight optimization methods. The iterative, second-order nature of the filter results in a large number of calculations for each sweep of the training set. This can increase the training time dramatically when training is conducted with data sets that contain large numbers of training patterns. In this paper an adaptive variant of the global, extended Kalman filter that exhibits substantially improved convergence properties is presented and discussed. The adaptive mechanism permits more rapid convergence of network training by identifying data that contain redundant information and avoiding calculations based on this redundant information.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180080605
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  • 8
    Electronic Resource
    Electronic Resource
    Simultaneous assay of serum vitamin A and vitamin E by high performance liquid chromatography using time-switched UV and fluorimetric detectors (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 281-284 
    Details
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Time-switched detectors ; UV detection ; Fluorimetric detection ; Vitamin A ; Vitamin E ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An HPLC method utilizing a UV and a fluorimetric detector linked in series is described. By use of a simple integrator-controlled time-switched relay, analysis of serum vitamin A and E is accomplished on the same chromatogram and at optimum sensitivity for each detector. A single internal standard (retinyl acetate) monitored only by the UV detector permits measurement of both vitamins over a wide linear range. Precision of the assays is satisfactory, both on a within-day and on a day-to-day basis. Recoveries of both vitamins are virtually 100% whilst sensitivity is 2 μg/L (retinol) and 0.05 mg/L (α-tocopherol).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240090506
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  • 9
    Electronic Resource
    Electronic Resource
    Steroid analysis by gas chromatography with SCOT and wide-bore WCOT columns (1980)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 241-247 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Quantitative analysis at 10-10g level ; Steroids in urine ; Amino acid fluorobutyrates (19 in 35 min) ; Installation of glass capillaries ; Connection to FM-ECD ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Glass capillary columns are ideal for analysis of urinary steroid profiles (i.e. the total steroid neutral fraction without prior separation into sub-groups).In this paper performance of both SCOT and wide-bore WCOT columns has been compared, resulting in no significant quantitative difference on urine extracts run as trimethylsilyl ether derivatives. However, because of increased efficiency the WB-WCOT column exhibited more sensitivity in measurement of small amounts of 11-ox-aetiocholanolone. Sensitivity of other steroids was greatly enhanced by use of either SCOT or WB-WCOT, leading to an almost tenfold increase over conventional packed columns (e.g. androsterone and aetiocholanolone 〈 40 μg per 24 h urine sample). A simple splitless injection system (based on a design of Dr. W. Greenaway, Oxford University) is presented.Experiments were also carried out using a SCOT column in conjunction with an FM-electron capture detector. Whilst efficiency was impaired due to the design of the detector, use of He (carrier) and N2 (make up gas) showed that several steroid derivatives could be easily measured at well below the 10-10 g level with much more rapid retention times than with a 1½m packed column. Highly successful separation of 19 amino acids (as fluoro-acyl derivatives) was achieved in 35 minutes using a SCOT (30 m) SP2100 column.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240030504
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  • 10
    Electronic Resource
    Electronic Resource
    Fortschritte in der Synthese von 19-nor-Steroiden (1964)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 76 (1964), S. 249-258 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In dieser Arbeit werden verbesserte Wege zur Darstellung von 19-nor-Steroiden beschrieben. Sie beruhen auf neuen Totalsynthesen des Östrons und auf der intramolekularen Funktionalisierung und Eliminierung der Methylgruppe C-19 in Androstan-Derivaten.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19640760603
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