Quantitative enzyme studies (17a-hydroxylase, 17,20-desmolase, 21-hydroxylase, and 20a-hydrox-ydehydrogenase), using as a source of enzyme small fragments (25-48 rag) of estrogeninduced testicular interstitial cell (Leydig cell) tumors of mice and their first generation transplants in castrate male isogeneic hosts, show rather conclusively that such tumors are composed of heterogeneous populati...

In the title compound, C(17)H(18)N(4)O(2)S·H(2)O, the thio-urea derivative is almost planar, with an r.m.s. deviation for the non-H atoms of 0.057 Å. The hydroxyl groups lie to the same side of the mol-ecule as the thione S atom, a conformation that allows the formation of intra-molecular O-H⋯S and O-H⋯N hydrogen bonds. In the crystal structure, the thio-urea and water mol-ecules self-assemble ...

In the crystal structure of the title salt, NH(4) (+).[(C(6)H(5))P(O)(2)(OH)](-) or NH(4) (+)·C(6)H(6)O(3)P(-), the N and O atoms inter-act via hydrogen bonds to generate a layer motif. The phenyl rings are stacked above and below this layer, sandwiching the hydrogen-bonded layer.

Bacillus subtilis uses glutamine as the best source of nitrogen. In the absence of glutamine, alternative nitrogen sources such as ammonium can be used. Ammonium utilization involves the uptake of the gas or the ammonium ion, the synthesis of glutamine by the glutamine synthetase and the recycling of the glutamate by the glutamate synthase. In this work, ammonium transport in B. subtilis was st...

RATIONALE Because of the threat of bombings using improvised explosives containing ammonium nitrate (AN), law enforcement and intelligence communities have been interested in stable isotope techniques for tracking and discriminating AN sources. Separate analysis of the AN component ions ammonium and nitrate would add discriminatory power to these techniques. METHODS Ammonium ions in dissolved...

Biological rapid sand filters are often used to remove ammonium from groundwater for drinking water supply. They often operate under dynamic substrate and hydraulic loading conditions, which can lead to increased levels of ammonium and nitrite in the effluent. To determine the maximum nitrification rates and safe operating windows of rapid sand filters, a pilot scale rapid sand filter was used ...

The effects of increasing ammonium concentrations in combination with different pH levels were studied on five heathland plant species to determine whether their occurrence and decline could be attributed to ammonium toxicity and/or pH levels. Plants were grown in growth media amended with four different ammonium concentrations (10, 100, 500 and 1000 micromol l(-1)) and two pH levels resembling...

Stable flies are blood feeding parasites and serious pests of livestock. The immature stages develop in decaying materials which frequently have high ammonium content. We added various ammonium salts to our laboratory stable fly rearing medium and measured their effect on size and survival as well as the physical properties of the used media. The addition of ammonium hydroxide, ammonium phospha...