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10 divided doses over a 5-day period. Hence it may be presumed that either the TSH-inhibitor was not longacting or the endogenously secreted TSH was not neutralized.Thus far the urinary preparations have been II tilized successfully to repress onlj. esogenous TSH effect on the thj-roid. S i r i i i i i i n r~~. A technic for detection of TSHinhibitor in human urinary preparations is described. For an effective partial 1)Iock of TSH response. mg amounts of a urinary preparation were injected one or more hours hefore an i 11 t r;i per i t (meal s t in1 iila t ory dose of TSH . 'I'SH resl)oiise was then nieasured using ll:;' blood le\-el5 \vhich wcrc sigiii ficantly decreased fol1ou.i ti? ad tiiinist r;i tion of iiri tiit rj' 'I'SH-in-1iil)itor.Grateful acknowledgement is given to Paul Starr ior advice and guidance.Thp i?utritional sicniiicancc of the lipids present in the serum medium common1~-uL;eil for growiny iii;iiiiliiiili;iii cell i in tissue cillturc is little uiitierstootl. 'I'he c f k t of seriim lipids on growth has been studied by Raker ant1 Carrel ( 1 ) and a bimilar .;tiid!o n 1it)ids from embryonic tissues w a~ made hj-(iiudetti ( 2 ) . Davitlson rt nl. ( 3 ) measured thc changinq ~ipid compo4ti:)n of chick licart e\;plants during growth. ant1 Simms ct (11. ( 4) studied factors affecting fat rlepo4tion in d r o . \'erne ( 5 ) has esaniined the effect of various compotindc; of biological orii'in on lipid m e t a h lism in tissue cultures. ('holesterol and fatty acids mere included in the cheniicallj-defined medium of Evans rt (I/.( 6 ) . I)ut it was later reported that there was no noticeahle effect on growth when these were omitted (ha). Sato, ..1;isher and puck ( 7 ) claim that addition of sniall amounts of cholesterol to a medium containing eshawtively dialysed serum, increased the plating efficiencj-of HeLa cells many fold. Kutstein r t nl. (20) have studied cholesterol ul)take by primary explants from human aorta. and cholesterol synthesis from labelled acetate has been demonstrated for the L strain of mouse filmblasts(8) and for a strain of hunian uterine fibroblasts( 9 ) . Azarnoff (10) has noted differences in the ability to synthesize cholesterol between cells from different species. We have studied the differential uptake of the various components of the serum lil'itls using principally the ME IT1 strain of niouse Iymphohlasts ( 11 ) as our model system. I\-e have also examined a number of other cell lines. but in less detail. The pattern of lipid uptake for each was similar to that observed with the ATH 111 cell, so that it may be as-~i i i e t l that the results o1)tained hy the more tlrtailetl t.satiiiri:itioli of the MH JTT system ;ire fairly typical. ildutcviuls und wwteth)ds. Human placenta1 cord serum, ox embryo extract and balanced

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