8-Arginine]-vasopressinoic acid: an inhibitor of rabbit kidney adenyl cyclase   总被引：6，自引：0，他引：6  

T Dousa  O Hechter  R Walter  I L Schwartz 《Science (New York, N.Y.)》1970,167(921):1134-1135

Neurohypophyseal hormnones and several synthetic analogs stimulate adenyl cyclase prepared from rabbit kidney medullary tissue. [8-Arginine]-vasopressinoic acid inhibits the stimulation of medullary adenyl cyclase by neurohypophyseal peptides but does not influence the action of parathyroid hormone on adenyl cyclase from kidiney cortex.  相似文献   

Molecular biology of learning: modulation of transmitter release   总被引：82，自引：0，他引：82  

E R Kandel  J H Schwartz 《Science (New York, N.Y.)》1982,218(4571):433-443

Until recently, it has been impossible to approach learning with the techniques of cell biology. During the past several years, elementary forms of learning have been analyzed in higher invertebrates. Their nervous systems allow the experimental study of behavioral, neurophysiological, morphological, biochemical, and genetic components of the functional (plastic) changes underlying learning. In this review, we focus primarily on short-term sensitization of the gill and siphon reflex in the marine mollusk, Aplysia californica. Analyses of this form of learning provide direct evidence that protein phosphorylation dependent on cyclic adenosine monophosphate can modulate synaptic action. These studies also suggest how the molecular mechanisms for this short-term form of synaptic plasticity can be extended to explain both long-term memory and classical conditioning.  相似文献   

Malignant lymphomas following allogenic disease: transition from an immunological to a neoplastic disorder   总被引：17，自引：0，他引：17  

R S Schwartz  L Beldotti 《Science (New York, N.Y.)》1965,149(691):1511-1514

The graft versus host reaction which occurs in F(1) hybrid mice injected with parental spleen cells was used to examine several immunological theories of neoplasia. Long-term survivors of this reaction developed lymphoid neoplasms which resembled Hodgkin's disease and lymphosarcoma. Mice with these tumors were chimeras, but the parental cells present within their spleens had specific immunological tolerance toward host antigens. This, together with the finding that the tumors were transplantable only to isogenic recipients, indicates that the tumors were of host rather than donor origin.  相似文献   

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   

Buying into the food system: Trends in food retailing in the US and implications for local foods     

Amy Guptill  Jennifer L. Wilkins 《Agriculture and Human Values》2002,19(1):39-51

The contemporary US food systemis characterized by both an unprecedentedconcentration of corporate control as well as afragmentation of sourcing and marketingprocesses, introducing both new constraints andnew opportunities for more localized foodsystems. The purpose of our study is to explorethese issues by investigating three keyquestions. First, what are the key trends inthe US grocery industry? Second, how dodifferent kinds of food outlets choose,procure, and promote food products? Finally,what are the implications of recent trends inthe food retailing process for strengtheninglocal flows of the production, distribution,and consumption of food? Background informationon the grocery industry and the results ofseven open-ended interviews conducted withowners and managers of grocery stores in oneupstate New York county indicate that theretailing process differs in complex ways fromstore to store and in most aspects cannot beinferred from store type. The paper concludeswith a discussion of the implications of ourfindings for local food system efforts,specifically in terms of new collaborationsamong producers, distributors, retailers, andshoppers, who play an indispensable role indeveloping viable alternatives to increasingcorporate control.  相似文献   

X-ray Photoelectron Spectroscopic Studies of Interactions in Multicomponent Metal and Metal Oxide Thin Films     

Winograd N  Baitinger WE  Amy JW  Munarin JA 《Science (New York, N.Y.)》1974,184(4136):565-567

Changes in chemical oxidation states in alloys and at solid-solid interfaces were monitored by using x-ray photoelectron spectroscopy. For an oxidized Nichrome surface, the chromium component was selectively converted to chromic oxide while nickel remained in the metallic state. When this surface was overlaid with a 20-angstrom-thick aluminum film, the chromic oxide was reduced to chromium and the aluminum was oxidized to aluminum oxide in a reaction zone consisting of no more than 10 angstroms of the interface. This scheme appeared general for solid-solid contacts and was predicted, to a first approximation, by bulk thermodynamic free energies.  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   

Regulation of bone mass in mice by the lipoxygenase gene Alox15     

Klein RF  Allard J  Avnur Z  Nikolcheva T  Rotstein D  Carlos AS  Shea M  Waters RV  Belknap JK  Peltz G  Orwoll ES 《Science (New York, N.Y.)》2004,303(5655):229-232

The development of osteoporosis involves the interaction of multiple environmental and genetic factors. Through combined genetic and genomic approaches, we identified the lipoxygenase gene Alox15 as a negative regulator of peak bone mineral density in mice. Crossbreeding experiments with Alox15 knockout mice confirmed that 12/15-lipoxygenase plays a role in skeletal development. Pharmacologic inhibitors of this enzyme improved bone density and strength in two rodent models of osteoporosis. These results suggest that drugs targeting the 12/15-lipoxygenase pathway merit investigation as a therapy for osteoporosis.  相似文献