Renewal of noradrenaline in different zones of the central nervous system of inbred mice strains and their recombinants]

A good correlation exists between the learning capacity and norepinephrine metabolism in the neocortex of C57 and Balb inbred Mice strains, as well as their F1 hybrids and seven recombinant inbred strains derived from their cross. The animals with a better learning performance are characterised by low levels of norepinephrine, as well as a slow metabolic rate of this neurotransmitter in the cortex. Such a correlation has not been found to exist in the other cerebral regions studied.     

Magnetostratigraphy of the Zanda basin in southwest Tibet Plateau and its tectonic implications

The Zanda basin is one of the very important basins at the north slope of the Himalaya Range. Thus the study of the basin strata will provide critical information about the tectonic evolution of the Himalayan Orogenic Belt. 268 oriented block samples were collected in the 750-m-thick sections of the Zanda basin. The characteristic remanent magnetization （ChRM） was isolated that decays linearly to the origin between 500℃ and 690℃for most studied samples. An age range of 9.5-2.6 Ma was estimated from the correlation between our observed polarity column and the Geomagnetic Polarity Time Scale （GPTS）. The age of the Zanda basin does not support the models that the South Tibetan Detach system （STDS） is one of the basin controlling faults. Given the sedimentological features in the basin and the tectonic features at the north edge of the basin, the Zanda basin was a half graben that was possibly controlled by the Karakorum fault on the northeast.     

Slow dust in Enceladus' plume from condensation and wall collisions in tiger stripe fractures

One of the spectacular discoveries of the Cassini spacecraft was the plume of water vapour and icy particles (dust) originating near the south pole of Saturn's moon Enceladus. The data imply considerably smaller velocities for the grains than for the vapour, which has been difficult to understand. The gas and dust are too dilute in the plume to interact, so the difference must arise below the surface. Here we report a model for grain condensation and growth in channels of variable width. We show that repeated wall collisions of grains, with re-acceleration by the gas, induce an effective friction, offering a natural explanation for the reduced grain velocity. We derive particle speed and size distributions that reproduce the observed and inferred properties of the dust plume. The gas seems to form near the triple point of water; gas densities corresponding to sublimation from ice at temperatures less than 260 K are generally too low to support the measured particle fluxes. This in turn suggests liquid water below Enceladus' south pole.     

Diffusion loading conditions determine recovery of protein synthesis in electroporated P3X63Ag8 cells

Using the suspension cell line P3X63Ag8 we have studied the impact of the composition of the diffusion medium on cellular protein synthesis under standard electroporation conditions in TBS-Na. This buffer contains the high saline concentration usually present in electroporation-mediated DNA transfection. Electroporation in the presence of TBS-Na resulted in an immediate shut-off of protein synthesis, even though both FITC-dextran (Mr 40 kD) and Semliki Forest virus core protein (Mr 33 kD) were incorporated efficiently into the cytoplasm across the electropores at 0 degrees C. Subsequent resealing of the pores was completed after a 5-min incubation at 37 degrees C. When compared with control cells, overall protein synthesis of electroporated cells recovered slowly to resume a 30% activity after 1 h of incubation at 37 degrees C. We have determined optimal conditions for diffusion loading (which necessitates the presence of ATP, GTP, amino acids, K+, Mg2+, and Ca2+) and resealing (in the presence of K+, Mg2+, and Ca2+), leading to a full and lasting recovery of protein synthesis within 5 min after pore closure.     

Diffusion loading conditions determine recovery of protein synthesis in electroporated P3X63 Ag8 cells

Summary Using the suspension cell line P3X63 Ag8 we have studied the impact of the composition of the diffusion medium on cellular protein synthesis under standard electroporation conditions in TBS-Na. This buffer contains the high saline concentration usually present in electroporation-mediated DNA transfection. Electroporation in the presence of TBS-Na resulted in an immediate shut-off of protein synthesis, even though both FITC-dextran (M_r 40 kD) and Semliki Forest virus core protein (M_r 33 kD) were incorporated efficiently into the cytoplasm across the electropores at 0°C. Subsequent resealing of the pores was completed after a 5-min incubation at 37°C. When compared with control cells, overall protein synthesis of electroporated cells recovered slowly to resume a 30% activity after 1 h of incubation at 37°C. We have determined optimal conditions for diffusion loading (which necessitates the presence of ATP, GTP, amino acids, K⁺, Mg²⁺, and Ca²⁺) and resealing (in the presence of K⁺, Mg²⁺, and Ca²⁺), leading to a full and lasting recovery of protein synthesis within 5 min after pore closure.     

High-velocity streams of dust originating from Saturn

High-velocity submicrometre-sized dust particles expelled from the jovian system have been identified by dust detectors on board several spacecraft. On the basis of periodicities in the dust impact rate, Jupiter's moon Io was found to be the dominant source of the streams. The grains become positively charged within the plasma environment of Jupiter's magnetosphere, and gain energy from its co-rotational electric field. Outside the magnetosphere, the dynamics of the grains are governed by the interaction with the interplanetary magnetic field that eventually forms the streams. A similar process was suggested for Saturn. Here we report the discovery by the Cassini spacecraft of bursts of high-velocity dust particles (> or = 100 km s(-1)) within approximately 70 million kilometres of Saturn. Most of the particles detected at large distances appear to originate from the outskirts of Saturn's outermost main ring. All bursts of dust impacts detected within 150 Saturn radii are characterized by impact directions markedly different from those measured between the bursts, and they clearly coincide with the spacecraft's traversals through streams of compressed solar wind.     

A salt-water reservoir as the source of a compositionally stratified plume on Enceladus

The discovery of a plume of water vapour and ice particles emerging from warm fractures ('tiger stripes') in Saturn's small, icy moon Enceladus raised the question of whether the plume emerges from a subsurface liquid source or from the decomposition of ice. Previous compositional analyses of particles injected by the plume into Saturn's diffuse E ring have already indicated the presence of liquid water, but the mechanisms driving the plume emission are still debated. Here we report an analysis of the composition of freshly ejected particles close to the sources. Salt-rich ice particles are found to dominate the total mass flux of ejected solids (more than 99 per cent) but they are depleted in the population escaping into Saturn's E ring. Ice grains containing organic compounds are found to be more abundant in dense parts of the plume. Whereas previous Cassini observations were compatible with a variety of plume formation mechanisms, these data eliminate or severely constrain non-liquid models and strongly imply that a salt-water reservoir with a large evaporating surface provides nearly all of the matter in the plume.