Search Results - (Author, Cooperation:R. C. Thomas)
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1Latest Papers from Table of Contents or Articles in PressP. E. Nugent ; M. Sullivan ; S. B. Cenko ; R. C. Thomas ; D. Kasen ; D. A. Howell ; D. Bersier ; J. S. Bloom ; S. R. Kulkarni ; M. T. Kandrashoff ; A. V. Filippenko ; J. M. Silverman ; G. W. Marcy ; A. W. Howard ; H. T. Isaacson ; K. Maguire ; N. Suzuki ; J. E. Tarlton ; Y. C. Pan ; L. Bildsten ; B. J. Fulton ; J. T. Parrent ; D. Sand ; P. Podsiadlowski ; F. B. Bianco ; B. Dilday ; M. L. Graham ; J. Lyman ; P. James ; M. M. Kasliwal ; N. M. Law ; R. M. Quimby ; I. M. Hook ; E. S. Walker ; P. Mazzali ; E. Pian ; E. O. Ofek ; A. Gal-Yam ; D. Poznanski
Nature Publishing Group (NPG)
Published 2011Staff ViewPublication Date: 2011-12-16Publisher: Nature Publishing Group (NPG)Print ISSN: 0028-0836Electronic ISSN: 1476-4687Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsPublished by: -
2Articles: DFG German National LicensesEdwards, Malcolm J. ; Thomas, R. C. ; Wong, Y. L.
Oxford, UK : Munksgaard International Publishers
Published 2003Staff ViewISSN: 1600-0560Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: MedicineNotes: Background: The aberrant expression of both the retinoblastoma and p53 tumor suppressor genes has been associated with more aggressive tumors, metastasis and lower survival.Methods: We have evaluated immunohistochemically the expression of pRB in a panel of non-melanoma skin cancers containing p53 somatic mutations.Results: Nuclear anti-p53 staining was detected in 18 (72%) differentiated squamous cell carcinomas, six (100%) undifferentiated squamous cell carcinomas and seven (28%) basal cell carcinomas. A correlation was observed between p53 expression and the proliferative activity of differentiated squamous cell carcinomas (P 〈 0.066), undifferentiated squamous cell carcinomas (P 〈 0.05) and basal cell carcinomas (P 〈 0.01). Tumors were selected for mutant p53 expression by PCR-directed DNA sequencing and pRB expression measured immunohistochemically. Anti-pRB reactivity was detected in the nuclei of basal and suprabasal layer cells of normal epidermis, and in the proliferative compartment of all the differentiated squamous cell carcinomas, and basal cell carcinomas. A correlation was observed between pRB expression and the proliferative activity of the differentiated squamous cell carcinomas (P 〈 0.01) and basal cell carcinomas (P 〈 0.025). However, anti-pRB reactivity was not detected in the six anti-p53 reactive undifferentiated squamous cell carcinomas.Type of Medium: Electronic ResourceURL: -
3Articles: DFG German National LicensesStaff View
ISSN: 1476-4687Source: Nature Archives 1869 - 2009Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsNotes: [Auszug] Fig. 1 Diagrammatic illustration of the preparation pinned into the experimental chamber. It was superfused continuously, and impaled with a conventional, KCl-filled microelectrode (left), and the pH-sensitive microelectrode (right). A diagram (not to scale) of 0.2 mm of the tip of the latter is ...Type of Medium: Electronic ResourceURL: -
4Articles: DFG German National LicensesStaff View
ISSN: 1476-4687Source: Nature Archives 1869 - 2009Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsNotes: [Auszug] Various mechanisms have been proposed6,7 to explain the mechanism of the H+ pumps involved in both pHi control and acid secretion by the stomach. Some of these mechanisms are outlined in Fig. 1. Schemes a?d involve the net transfer of charge across the cell membrane, and would thus be ...Type of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesStaff View
ISSN: 1476-4687Source: Nature Archives 1869 - 2009Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsNotes: [Auszug] In early experiments, the Li+-selective ligand was used to make macroelectrodes by incorporation in a polyvinylchloride (PVC) membrane using Tris-(2-ethylhexyl)-phosphate (TEHP) as plasticiser. The response characteristics of such a membrane are shown in Fig. 1 (refs 4 and 5). According to Fig. 1, ...Type of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesStaff View
ISSN: 1476-4687Source: Nature Archives 1869 - 2009Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsNotes: [Auszug] Cats were anaesthetized with chloralose-urethane, placed in a stereotaxic head holder and later paralysed with ?Flaxedil? and artificially respired. A lumbar laminectomy was performed and various leg nerves in both hind limbs were exposed and prepared for stimulation. In a number of animals the ...Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesStaff View
ISSN: 1476-4687Source: Nature Archives 1869 - 2009Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsNotes: [Auszug] Acute decapitate cats were prepared in the usual manner, and, after lumbosacral laminectomy, Renshaw cells were located and the characteristic discharge of single units identified as previously described1,5. The electrodes used for recording and marking were prepared by filling glass micropipettes ...Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesStaff View
ISSN: 1365-2044Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: MedicineType of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesStaff View
ISSN: 0307-1847Topics: Political ScienceURL: -
10Articles: DFG German National LicensesStaff View
ISSN: 0307-1847Topics: Political ScienceURL: -
11Articles: DFG German National LicensesStaff View
ISSN: 0307-1847Topics: Political ScienceURL: -
12Articles: DFG German National LicensesStaff View
ISSN: 1476-4687Source: Nature Archives 1869 - 2009Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsNotes: [Auszug] Experiments were done on exposed cells in isolated sub-oesophageal ganglia from the snail, Helix aspersa. The neuronal cell body was penetrated with four microelectrodes. The first was to measure pH7. The second was a reference liquid ion-exchanger electrode to measure Em8. The third, a ...Type of Medium: Electronic ResourceURL: -
13Articles: DFG German National LicensesStaff View
ISSN: 1476-4687Source: Nature Archives 1869 - 2009Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsNotes: [Auszug] We performed our experiments on the largest nerve cell at the rear of the right pallial ganglion of the common snail Helix aspersa. The brain was dissected from dormant specimens and pinned in a chamber where it was bathed in continuously flowing snail Ringer (KC1,4 mM; NaCl, 80 mM; CaCl2, 7 mM; ...Type of Medium: Electronic ResourceURL: -
14Articles: DFG German National LicensesAlthaus, I. W. ; Chou, J. J. ; Gonzales, A. J. ; LeMay, R. J. ; Deibel, M. R. ; Chou, K. -C. ; Kezdy, F. J. ; Romero, D. L. ; Thomas, R. C. ; Aristoff, P. A. ; Tarpley, W. G. ; Reusser, F.
Springer
Published 1994Staff ViewISSN: 1420-9071Keywords: HIV RT ; polysulfonate ; inhibitor ; steady-state kineticsSource: Springer Online Journal Archives 1860-2000Topics: BiologyMedicineNotes: Abstract The tetramer of ethylenesulfonic acid (U-9843) is a potent inhibitor of HIV-1 RT* and possesses excellent antiviral activity at nontoxic doses in HIV-1 infected lymphocytes grown in tissue culture. Kinetic studies of the HIV-1 RT-catalyzed RNA-directed DNA polymerase activity were carried out in order to determine if the inhibitor interacts with the template: primer or the deoxyribonucleotide triphosphate (dNTP) binding sites of the polymerase. Michaelis-Menten kinetics, which are based on the establishment of a rapid equilibrium between the enzyme and its substrates, proved inadequate for the analysis of the experimental data. The data were thus analyzed using steady-state Briggs-Haldane kinetics assuming that the template:primer binds to the enzyme first, followed by the binding of the dNTP and that the polymerase is a processive enzyme. Based on these assumptions, a velocity equation was derived which allows the calculation of all the specific forward and backward rate constants for the reactions occurring between the enzyme, its substrates and the inhibitor. The calculated rate constants are in agreement with this model and the results indicated that U-9843 acts as a noncompetitive inhibitor with respect to both the template:primer and dNTP binding sites. Hence, U-9843 exhibits the same binding affinity for the free enzyme as for the enzyme-substrate complexes and must inhibit the RT polymerase by interacting with a site distinct from the substrate binding sites. Thus, U-9843 appears to impair an event occurring after the formation of the enzyme-substrate complexes, which involves either an event leading up to the formation of the phosphoester bond, the formation of the ester bond itself or translocation of the enzyme relative to its template:primer following the formation of the ester bond.Type of Medium: Electronic ResourceURL: -
15Articles: DFG German National LicensesStaff View
ISSN: 1432-2013Keywords: Intracellular pH ; Weak acid and base ; Buffering powerSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract From the combined Henderson-Hasselbalch relations for a weak acid and a weak base, we derive an expression for steady-state intracellular pH(pHi). The derivation requires only accurate measurements of the pHi changes when the two electrolytes are applied, rather than absolute values. The method is based on the assumption of equilibrium of the neutral forms of the two compounds across the plasma membrane, that is, absence of permeation of the charged forms. It is also assumed that no significant pHi regulation takes place, that there is no significant permeability to intracellular buffers and that intracellular buffering power, over the measured span of pHi, is the same. This precludes the use of CO2/bicarbonate buffered systems. We find that under our experimental conditions steady-state pHi values calculated in this way agree closely with those measured directly with pH-sensitive microelectrodes both in snail neurones and crab muscle. The method would allow the intracellular calibration of other pHi measuring techniques.Type of Medium: Electronic ResourceURL: -
16Articles: DFG German National LicensesStaff View
ISSN: 1432-2013Keywords: EIPA Na+-dependent Cl–/HCO3– exchange Na+/H+ exchange pH regulation Snail neuronesSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Abstract. We have used the pH-sensitive fluorescent dye 8-hydroxypyrene-1,3,6-trisulphonic acid (HPTS) to re-examine the mechanisms that extrude acid from voltage-clamped Helix aspersa neurones. Intracellular acid loads were imposed by three different methods: application of weak acid, depolarization and removal of extracellular sodium. In nominally CO2/HCO3-free Ringer the rate of recovery from acid loads was significantly slowed by the potent Na+/H+ exchange inhibitor 5-[N-ethyl-N-isopropyl]-amiloride (EIPA, 50 µM). Following depolarization-induced acidifications the rate of intracellular pH (pHi) recovery was significantly reduced from 0.41±0.13 pH units.h–1 in controls to 0.12±0.09 pH units.h–1 after treatment with EIPA at pHi ≅7.3 (n=7). The amiloride analogue also reduced the rate of acid loading seen during extracellular sodium removal both in the presence and absence of the Na+-dependent Cl–/HCO3 – exchange inhibitor 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulphonic acid (SITS, 50 µM). This is consistent with EIPA inhibiting reverse-mode Na+/H+ exchange. In 2.5% CO2/20 mM HCO3-buffered Ringer pHi recovery was significantly inhibited by SITS, but unaffected by EIPA. Our results indicate that there are two separate Na+-dependent mechanisms involved in the maintenance of pHi in Helix neurones: Na+-dependent Cl–/HCO3 – exchange and Na+/H+ exchange. Acid extrusion from Helix neurones is predominantly dependent upon the activity of Na+-dependent Cl–/HCO3 – exchange with a lesser role for Na+/H+ exchange. This adds further weight to the belief that the Na+/H+ exchanger is ubiquitous.Type of Medium: Electronic ResourceURL: -
17Articles: DFG German National LicensesStaff View
ISSN: 0269-3879Keywords: Chemistry ; Analytical Chemistry and SpectroscopySource: Wiley InterScience Backfile Collection 1832-2000Topics: MedicineNotes: A method for the unambiguous characterization of DNA photoproducts has been developed. It does not require radio-labelled DNA, or specialized techniques. In the preliminary step, UV-irradiated DNA is hydrolysed to its constituent bases and photoproducts. The photoproducts are then separated from nucleic acid bases using low pressure ion-exchange chromatography on a Dowex 1 × 8 200-400, and an Amberlite CG-50-H+ column. Further separation and purification of photoproducts is carried out on the HPLC Whatman Partisil ODS2 column, using 15% MeOH. The procedure is simple, reproducible and versatile.Additional Material: 2 Ill.Type of Medium: Electronic ResourceURL: -
18Articles: DFG German National LicensesZias, A. R. ; Clapp, C. W. ; DeMichele, D. J. ; Emtage, P. R. ; Hartman, D. K. ; Savery, J. W. ; Thomas, R. C.
Springer
Published 1963Staff ViewISSN: 1741-2765Source: Springer Online Journal Archives 1860-2000Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision MechanicsNotes: Abstract A particular transducer application of a piezoresistive semiconductor is presented. This application and its associated engineering approaches are treated as a medium for (1) clarification of a structural engineering problem which arises in single-crystal semiconductor studies; and (2) definition of an error in the design approaches of suppliers and users of piezoresistive devices. The design approaches are based on two assertions: (1) the future of piezoresistive sensors lies in utilization of single-crystal semiconductor structural subsystems having sensors and circuits as integral parts of the singlecrystal structures, not in gluing, potting, soldering or alloying sensors and circuits to conventional structures; and (2) the design and positioning of future sensors with respect to stress-producing phenomena, and the instrumentation to properly tailor the piezoresistive response into intelligent signals should not resemble wire strain gages and piezoelectric devices. The design thinking applied to piezoresistive devices need not be prejudiced by today’s state-of-the-art.Type of Medium: Electronic ResourceURL: -
19Articles: DFG German National LicensesStaff View
ISSN: 1741-0444Source: Springer Online Journal Archives 1860-2000Topics: BiologyChemistry and PharmacologyMedicineDescription / Table of Contents: Sommaire Ce papier décrit une source de courant simple, transistorisée, à accroissement linéaire qui, avec un montage en pont, permet de balayer sur une échelle donnée le potentiel de la membrane nerveuse d'une façon répétée et répérer ainsi, rapidement, le potentiel à polarité inverse de l'IPSP (potentiels inhibiteurs post-synaptiques). La lenteur et la régularité des variations du potentiel de la membrane permet de présenter l'activité du IPSP à gain élevé par un tracé d'oscilloscope, tandis que le potentiel du courant continu est présenté par un tracé à gain moins élevé. Une série de déterminations du potentiel à polarité inverse de l'IPSP des neurones d'escargot immergés dans des solutions de concentrations différentes de Cl− et de K+ montre que pendant la durée de l'IPSP la cellule devient plus perméable à Cl− et K+, l'effet du chloride étant plus prononcé.Abstract: Zusammenfassung Dieser Artikel beschreibt eine einfache transistorisierte Quelle mit linear steigendem Strom, die in Verbindung mit einer Brückenschaltung gestattet, das Mempranpotential von Nerven wiederholt über einen gegebenen Bereich durchlaufen zu lassen. dadurch kann das Gegen potential der hemmenden postsynaptischen Potentiale (IPSP=inhibitory post synaptic potential) schnell bestimmt werden. Die Gleichmäßigkeit und die langsame Änderung des Membranpotentials ermöglichen es, den Wechselanteil des IPSP nach hoher Verstärkung mit dem einen Strahl des Oszillographen anzuzeigen, während der Gleichanteil bei niedriger Verstärkung mit dem anderen Strahl angezeigt wird. Aufeinanderfolgende Bestimmungen des Gegenpotentials des IPSP von Schnecken-Neuronen, die in Lösungen verschiedener Konzentration von Cl′ oder K+ getaucht wurden, zeigen, daß während des Bestehens des IPSP die Zellen für Cl′ und K+ mehr durchlässig werden und daß Cl′ die stärkere Wirkung hat.Notes: Abstract This paper describes a simple transistorized source of linearly increasing current which, used in conjunction with a bridge circuit, enables one to sweep the nerve membrane potential repeatedly over a given range and so make rapid determinations of the reversal potential of the inhibitory post synaptic potentials (IPSP). The smoothness and slowness of the membrane potential change enables the IPSP to be displayed at a high gain on the a.c. coupled beam of an oscilloscope whilst the d.c. potential is displayed on the other beam at lower gain. Sequential determinations of the IPSP reversal potential of snail neurones bathed in solutions containing different concentrations of Cl− or K+ show that during the IPSP, the cell becomes more permeable to Cl− and K+, the Cl− having the greater effect.Type of Medium: Electronic ResourceURL: