PS bioassay

P-Epoxyambelline (cavinine) (372) has been found to be an immu-nostimulant, and it produces moderate activation of mouse spleen lymphocytes (55). Although the epoxy alkaloid undulatine (371) was inactive in 9 PS and 3 PS screens, ambelline (368) did exhibit in vitro activity in the 9 PS bioassay (5). 

Scheme 2. Detailed chromatographic separation scheme for cephalostatins 5 and 6. Numbers in brackets refer to PS bioassay activity, in pg/ml.

In ritterazines F and G, C-22 is again epimeric to the configuration observed in ritterazine B ritterazine G has the additional modification of C-14,15 unsaturation. In the PS bioassay, ritterazines F and G have IC50 values of 7.3x1 O 4 pg/ml - the highest activity seen among the ritterazines apart from ritterazine B (note that this is still much lower than the activity of cephalostatin 1). 

Europium and terbium are the most frequently used lanthanides in bioassays. The labels based on Eu or Tb have normally luminescence lifetimes in the range of 500 ps to 1.5 ms. Samarium- and dysprosium-based labels are also commercially available. They have significantly shorter luminescence lifetimes and lower quantum efficiency, making them less optimal for current instrumentation. 

As screening capacity in the U.S. National Cancer Institute s P388 lymphocytic leukemia (PS) test increased in the 1965-1968 period it began to have a very beneficial impact on the success of our research directed at the discovery of marine animal antineoplastic constituents. The early (6) and more recent 13) evolutionary direction of the NCI antineoplastic and cytostatic evaluation systems has been reviewed. By 1968 extracts of B. neritina reached the confirmed active level and consistently allowed over a 100% increase in life span. Bioassay guided isolation was begun with the PS in vivo system and supplemented from 1975 on with the PS in vitro cell line. The in vivo and in vitro activity... 

Boucher, S.E., S. Calsamiglia, C.M. Parsons, H.H. Stein, M.D. Stem, PS. Erickson, P.L. Utterback and C.G. Schwab, 2009. Intestinal digestibility of amino acids in rumen undegradable protein estimated using a precission-fed cecectomized rooster bioassay Soybean meal and SoyPlus. J. Dairy Sci. 92, 4489-4498. 

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