Thyrotropin and cyclic nucleotide effects on prostaglandin levels in isolated thyroid cells

Thyrotropin increases prostaglandin levels in isolated thyroid cells. Since comparable results were obtained with butyrated cyclic adenosine monophosphate derivatives as well as with the phosphodiesterase inhibitors quazodine and theophylline, it appears that cyclic adenosine monophosphate mediates this effect of thyrotropin. These observations suggest that intracellular prostaglandins play a role in modulating thyrotropin action on thyroid.     

Global-scale similarities in nitrogen release patterns during long-term decomposition

Litter decomposition provides the primary source of mineral nitrogen (N) for biological activity in most terrestrial ecosystems. A 10-year decomposition experiment in 21 sites from seven biomes found that net N release from leaf litter is dominantly driven by the initial tissue N concentration and mass remaining regardless of climate, edaphic conditions, or biota. Arid grasslands exposed to high ultraviolet radiation were an exception, where net N release was insensitive to initial N. Roots released N linearly with decomposition and exhibited little net N immobilization. We suggest that fundamental constraints on decomposer physiologies lead to predictable global-scale patterns in net N release during decomposition.     

Spectral line interferometry with independent time standards at stations separated by 845 kilometers

An upper limit of 0.02 second of arc has been determined for a hydroxyl radical (OH) emission region associated with the radio source W3, with the use of a Michelson interferometer consisting of two radio telescopes 845 kilometers apart. Timing was provided at the stations by independent atomic frequency standards. The 1665-megahertz radiation was translated to video frequency and recorded digitally on magnetic tapes which were later processed by computer, yielding fringe phase and amplitude as a function of frequency over the received bandwidth.     

Chicxulub multiring impact basin: size and other characteristics derived from gravity analysis

The buried Chicxulub impact structure in Mexico, which is linked to the Cretaceous- Tertiary (K-T) boundary layer, may be significantly larger than previously suspected. Reprocessed gravity data over Northern Yucatan reveal three major rings and parts of a fourth ring, spaced similarly to those observed at multiring impact basins on other planets. The outer ring, probably corresponding to the basin's topographic rim, is almost 300 kilometers in diameter, indicating that Chicxulub may be one of the largest impact structures produced in the inner solar system since the period of early bombardment ended nearly 4 billion years ago.     

Water Vapor Maser "Turn-On" in the HII Region W3 (OH)

A line in the water vapor maser spectrum of the HII region W3(OH) was observed to increase in brightness over an 8-day period and then decline to its original intensity over the following 4 weeks. The intensity variation can be explained by a simple maser model, with an impulse of energy suddenly applied. The observed time scale and energy output are consistent with a maser on the outskirts of a dust cocoon surrounding an O5 star, with a momentary "leak," lasting a day or. two, supplying the necessary energy.