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  • General Chemistry  (12)
  • Biochemistry and Biotechnology  (4)
  • Alzheimer's disease  (3)
  • Computational Chemistry and Molecular Modeling  (3)
  • Drosophila melanogaster  (3)
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  • 1
    ISSN: 1432-1432
    Keywords: Urate oxidase ; Drosophila pseudoobscura ; Drosophila melanogaster ; Nucleotide sequence ; Evolutionary comparison ; Gene regulation ; Malpighian tubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The urate oxidase (UO) transcription unit of Drosophila pseudoobscura was cloned, sequenced, and compared to the UO transcription unit from Drosophila melanogaster. In both species the UO coding region is divided into two exons of approximately equal size. The deduced D. pseudoobscura and D. melanogaster UO peptides have 346 and 352 amino acid residues, respectively. The nucleotide sequences of the D. pseudoobscura and D. melanogaster UO protein-coding regions are 82.2% identical whereas the deduced amino acid sequences are 87.6% identical with 42 amino acid changes, 33 of which occur in the first exon. Although the UO gene is expressed exclusively within the cells of the Malpighian tubules in both of these species, the temporal patterns of UO gene activity during development are markedly different. UO enzyme activity, UO protein, and UO mRNA are found in the third instar larva and adult of D. melanogaster but only in the adult stage of D. pseudoobscura. The intronic sequences and the extragenic 5′ and 3′ flanking regions of the D. pseudoobscura and D. melanogaster UO genes are highly divergent with the exception of eight small islands of conserved sequence along 772 by 5′ of the UO protein-coding region. These islands of conserved sequence are possible UO cis-acting regulatory elements as they reside along the 5′ flanking DNA of the D. melanogaster UO gene that is capable of conferring a wild-type D. melanogaster pattern of UO regulation on a UO-lacZ fusion gene.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Drosophila melanogaster ; Transcription map ; Faint bands ; Interband chromatin ; Polytene chromosomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Urate oxidase mRNA and five other transcripts map along 38 kb of DNA in the region 28C on the Drosophila melanogaster second chromosome. Three biotinylated restriction fragments from this 38 kb of DNA, one from each end and one from the middle, were individually hybridized in situ to slightly stretched salivary gland polytene chromosomes. The data from these in situ hybridizations in combination with the transcription map of the 38 kb of DNA indicate that: (i) there are six discrete RNA species encoded along the 38 kb of DNA and (ii) these six transcripts map to the faint band/interband region which includes the proximal edge of 280, the three faint bands, 28C2, 280 and 28C4-5(−), and the adjacent interband chromatin. Our data are consistent with the few published studies directly demonstrating that faint band/interband regions of the Drosophila melanogaster salivary gland polytene chromosomes code for a high density of transcripts.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 223-233 
    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
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  • 4
    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
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular neurobiology 20 (2000), S. 497-508 
    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
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 6 (1972), S. 663-668 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The diamagnetic susceptibility χ and magnetic shielding σ for H2+ are investigated in the range of internuclear separations R = 1.6 a.u. to R = 2.4 a.u. according to a previously reported technique. From this data values of 〈χ〉 and 〈σ〉, for which nuclear motion due to zero-point vibration and centrifugal stretching is taken into account, are calculated at 300°K. These averages are 〈χ〉 = -0.3902 α2ao3 and 〈σ〉 = 1.096 × 10-5 c.g.s. units which are approximately 3.1% and 1.4% respectively, smaller than the equilibrium values.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 6 (1972), S. 651-661 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variation-perturbation method, analogous to a technique devised by Das and Bersohn for the study of the hydrogen molecule, is developed for calculation of the diamagnetic susceptibility χ and magnetic shielding σ and is applied to a study of the hydrogen molecule ion. Two approximations are investigated-in a first approximation, χ = -0.37814α2ao3 and σ = 1.112 × 10-5 c.g.s. units and in a second approximation, χ = -0.37569α2ao3 and σ = 1.128 × 10-5 c.g.s. units.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 7 (1973), S. 635-636 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 443-451 
    ISSN: 0006-3592
    Keywords: osteoblast ; migration ; poly(αhydroxy esters) ; poly(DL-lactic-co-glycolic acid) ; PLGA ; biodegradable polymers ; tissue engineering ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We investigated the migration of rat calvaria osteoblast populations on poly(α-hydroxy ester) films for up to 14 days to determine effects of substrate composition and culture conditions on the migratory characteristics of osteoblasts. Initial osteoblast culture conditions included cell colonies formed by seeding a high (84,000 cells/cm2) or low (42,000 cells/cm2) density of isolated osteoblasts on the polymer films, and bone tissue cultures formed by plating bone chips directly on the substrates. High density osteoblast colonies cultured and allowed to migrate and proliferate radially on 85:15 poly(DL-lactic-co-glycolic acid) (PLGA) films, 75:25 PLGA films, and tissue culture polystyrene controls demonstrated that the copolymer ratio in the polymer films did not affect the rate of increase in substrate surface area (or culture area) covered by the growing cell colony. However, the rate of increase in culture area was dependent on the initial osteoblast seeding density. Initial cell colonies formed with a lower osteoblast seeding density on 75:25 PLGA resulted in a lower rate of increase in culture area, specifically 4.9 ± 0.3 mm2/day, versus 14.1 ± 0.7 mm2/day for colonies seeded with a higher density of cells on the same polymer films. The proliferation rate for osteoblasts in the high and low density seeded osteoblast colonies did not differ, whereas the proliferation rate for the osteoblasts arising from the bone chips was lower than either of these isolated cell colonies. Confocal and light microscopy revealed that the osteoblast migration occurred as a monolayer of individual osteoblasts and not a calcified tissue front. These results demonstrated that cell seeding conditions strongly affect the rates of osteoblast migration and proliferation on biodegradable poly(α-hydroxy esters). © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 92-114 
    ISSN: 0887-3585
    Keywords: phospholipid membranes ; permeation ; antibiotics ; computer simulations ; tryptophan ; water ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The microscopic details of lipid-protein interactions are examined using molecular dynamics simulations of the gramicidin A channel embedded in a fully hydrated dimyristoyl phosphatidylcholine (DMPC) bilayer. A novel construction protocol was used to assemble the initial configurations of the membrane protein complex for the simulations. Three hundreds systems were constructed with different initial lipid placement and conformations. Seven systems were simulated with molecular dynamics. One system was simulated for a total of 600 psec, four were simulated for 300 psec, and two for 100 psec. Analysis of the resulting trajectories shows that the bulk solvent-membrane interface region is much broader than traditionally pictured in simplified continuum theories: its width is almost 15 Å. In addition, lipid-protein interactions are far more varied, both structurally and energetically, than is usually assumed: the total interaction energy between the gramicidin A and the individual lipids varies from 0 to -50 kcal/mol. The deuterium quadrupolar splittings of the lipid acyl chains calculated from the trajectories are in good agreement with experimental data. The lipid chains in direct contact with the GA are ordered but the effect is not uniform due to the irregular surface of the protein. Energy decompositions shows that the most energetically favorable interactions between lipid and protein involve nearly equal contributions from van der Waals and electrostatic interactions. The tryptophans, located near the bulk-membrane interface, appear to be particularly important in mediating both hydrogen bonding interactions with the lipid glycerol backbone and water and also in forming favorable van der Waals contacts with the hydrocarbon chains. In contrast, the interactions of the leucine residues with the lipids, also located near the interface, are dominated by van der Waals interactions with the hydrocarbon lipid chains.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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