Renal concentrating mechanism: possible role for sodium-potassium activated adenosine triphosphatase   总被引：2，自引：0，他引：2  

M Martinez-Maldonado  J C Allen  G Eknoyan  W Suki  A Schwartz 《Science (New York, N.Y.)》1969,165(895):807-808

Sodium-potassium activated adenosine triphosphatase activity was found to be almost twice as high in renal medulla as in cortex. Infusion of digoxin, a specific inhibitor of the enzyme, into one renal artery of the dog resulted in unilateral natriuresis, impaired concentrating capacity, and reduction of the enzyme activity in both cortex and medulla. It is suggested that the sodium-potassium adenosine triphosphatase plays an important role in urine concentration mechanisms.  相似文献   

Sparing of the brain in neonatal undernutrition: amino acid transport and incorporation into brain and muscle     

L S Freedman  S Samuels  I Fish  S A Schwartz  B Lange  M Katz  L Morgano 《Science (New York, N.Y.)》1980,207(4433):902-904

Rates of tyrosine and lysine transport and incorporation into protein were measured in control and undernourished weanling rats. Undernutrition was induced by feeding lactating dams a low protein diet (12 percent casein) from birth to day 21. At weaning, body and brain weights of undernourished rats were 50 percent and 88 percent, respectively, of control values. Lysine and tyrosine transport rates into skeletal muscle were reduced by over 75 percent, more than twice the reduction seen in brain. Rates of amino acid incorporation into muscle protein were reduced by approximately 50 percent; the change in rate of incorporation into brain protein was not statistically significant. These data indicate that, in spite of marked retardation of amino acid transport into brain, the brain seems fully capable of maintaining normal rates of protein synthesis.  相似文献   

Phonon dispersions of fcc delta-plutonium-gallium by inelastic x-ray scattering     

Wong J  Krisch M  Farber DL  Occelli F  Schwartz AJ  Chiang TC  Wall M  Boro C  Xu R 《Science (New York, N.Y.)》2003,301(5636):1078-1080

We report an experimental determination of the phonon dispersion curves in a face-centered cubic (fcc) delta-plutonium-0.6 weight % gallium alloy. Several unusual features, including a large elastic anisotropy, a small-shear elastic modulus C', a Kohn-like anomaly in the T1[011] branch, and a pronounced softening of the [111] transverse modes, are found. These features can be related to the phase transitions of plutonium and to strong coupling between the lattice structure and the 5f valence instabilities. Our results also provide a critical test for theoretical treatments of highly correlated 5f electron systems as exemplified by recent dynamical mean field theory calculations for delta-plutonium.  相似文献   

Stable Semiconductor Liquid Junction Cell with 9 Percent Solar-to-Electrical Conversion Efficiency     

Chang KC  Heller A  Schwartz B  Menezes S  Miller B 《Science (New York, N.Y.)》1977,196(4294):1097-1099

The semiconductor liquid junction cell n-GaAs/0.8M K(2)Se-0.1M K(2)Se(2)-1M KOH/C has been shown to attain 9 percent photovoltaic power conversion efficiency in sunlight. Accelerated tests under 3100 degrees K light sources of several solar intensities indicate very low photocorrosion currents and high output stability.  相似文献   

Mental rotation of the neuronal population vector   总被引：19，自引：0，他引：19  

A P Georgopoulos  J T Lurito  M Petrides  A B Schwartz  J T Massey 《Science (New York, N.Y.)》1989,243(4888):234-236

A rhesus monkey was trained to move its arm in a direction that was perpendicular to and counterclockwise from the direction of a target light that changed in position from trial to trial. Solution of this problem was hypothesized to involve the creation and mental rotation of an imagined movement vector from the direction of the light to the direction of the movement. This hypothesis was tested directly by recording the activity of cells in the motor cortex during performance of the task and computing the neuronal population vector in successive time intervals during the reaction time. The population vector rotated gradually counterclockwise from the direction of the light to the direction of the movement at an average rate of 732 degrees per second. These results provide direct, neural evidence for the mental rotation hypothesis and indicate that the neuronal population vector is a useful tool for "reading out" and identifying cognitive operations of neuronal ensembles.  相似文献   

Biomedicine. Staying slim with insulin in mind     

Schwartz MW 《Science (New York, N.Y.)》2000,289(5487):2066-2067

Striking the delicate balance between energy intake in the form of food and energy expenditure in the form of metabolic activity keeps the body extremely busy. As Schwartz explains in his enlightening Perspective, the finding that insulin signals the brain to promote weight loss (Brüning et al.) flies in the face of the notion that insulin is involved solely in glucose storage, its conversion to fat, and weight gain.  相似文献   

Recombination of human mitochondrial DNA   总被引：1，自引：0，他引：1  

Kraytsberg Y  Schwartz M  Brown TA  Ebralidse K  Kunz WS  Clayton DA  Vissing J  Khrapko K 《Science (New York, N.Y.)》2004,304(5673):981

  相似文献   

Wilhelm Caspari, 1872-1944     

Schwartz E  Chambers R 《Science (New York, N.Y.)》1947,105(2737):613

  相似文献   

Surface order and stability of langmuir-blodgett films     

Schwartz DK  Garnaes J  Viswanathan R  Zasadzinski JA 《Science (New York, N.Y.)》1992,257(5069):508-511

Angstrom-resolution atomic force microscope images of Langmuir-Blodgett monolayers and multilayers of cadmium arachidate in air and under water show a dramatic change from a disordered arrangement to a crystalline lattice by the addition or removal of a single layer of molecules. The disordered surface is less stable than the ordered one to mechanical stresses such as atomic force microscopy tip forces or at the air-water contact line during contact angle measurements. The difference in the degree of order in the alkyl chains is attributed to the strong attractive interaction between headgroups in the presence of the divalent cation.  相似文献   

Characterization of T cell receptor gamma chain expression in a subset of murine thymocytes   总被引：43，自引：0，他引：43  

A M Lew  D M Pardoll  W L Maloy  B J Fowlkes  A Kruisbeek  S F Cheng  R N Germain  J A Bluestone  R H Schwartz  J E Coligan 《Science (New York, N.Y.)》1986,234(4782):1401-1405

While much information exists about the structure and function of the clonally distributed T cell receptor (TCR) alpha beta heterodimer, little is known about the gamma protein, the product of a third rearranging TCR gene. An antiserum to a carboxyl-terminal peptide common to several of the murine gamma chain constant regions and a monoclonal antibody to the murine T3 complex were used to identify products of this TCR gene family in a subpopulation of Lyt2-, L3T4- thymocytes. This subpopulation does not express TCR alpha or full-length TCR beta messenger RNA. The gamma chain is a 35-kilodalton (kD) protein that is disulfide-bonded to a 45-kD partner and is associated with the T3 complex. Analysis of the glycosylation pattern of this thymic gamma chain revealed that the major variable region gamma (V gamma) gene transcribed in activated peripheral T cells is absent from this subpopulation. The cells that bear this second T cell receptor may therefore represent a distinct lineage differentiating within the thymus.  相似文献