Abstract: Novel amides of an iodothyronine compound such as tri-iodothyronine (T3) or thyroxine (T4) with an aminoacetic acid compound such as nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) or diethylenetriamine pentaacetic acid (DTPA) may be labelled, e.g. radioactively labelled with I-125, to give labelled derivatives useful in assays of a free thyroid hormone in a biological fluid which also contains the thyroid hormone bound to one or more natural binders. The novel compound T4 EDTA is shown to bind much more strongly to antibodies to T4 than to the natural protein binders in the biological fluid.

Abstract: Novel compounds having the formula (II) ##STR1## where X is radioactive Se or Te, z is 0 or 1 and R is OH or an amino acid residue, particularly 23-[.sup.75 Se]-selena-25-homocholic acid and its glycine and taurine conjugate have outstandingly good properties for the investigation of bowel function.

Abstract: Body function of a mammal is investigated using a .gamma.-emitting .sup.75 Se or .sup.123m Te labelled derivative of a bile acid or bile salt. Thus bowel function may be investigated by oral administration of the labelled compound followed, after a suitable period of time, by either a whole body count or a faecal count of radioactivity. Preferred bile acids and salts are substituted either at the 19-position or in the C-17 side chain.

Abstract: Novel selenium-75 derivatives of folates, which are useful in competitive radio assay of folates, have the general formula: ##STR1## where a dotted bond line indicates that the bond may be single or double, and whereX is H or --CH.sub.3,m is 0 or 1 (such that the adjacent nitrogen atom is trivalent), and either(a) R is ##STR2## and is attached through the nitrogen atom to the pteroyl residue where q is 0 or 1p is 1 or 2Q is C.sub.x H.sub.2x+1 where x is from 1 to 6and when q is 0, Z is H and when q is 1, Z is HO, or(b) R is--CO.CHY.CHY.CH(COOH)NH--and is attached through the nitrogen atom to the pteroyl residue, where Z is HO,one group Y is --H and the other group Y is --SeC.sub.x H.sub.2x+1 where x is from 1 to 6 and esters and salts of such acid.

Abstract: The present invention provides compounds having the general formula ##STR1## wherein R is ##STR2## and A is 0 or 1,B is 0 to 4,C is 0 to 4,Z is Se or Te,R.sup.6 is --OH or an amino acid residue,R.sup.7 is hydrogen or saturated C.sub.1 to C.sub.4 alkyl group, when A is 1,R.sup.8 is hydrogen or saturated C.sub.1 to C.sub.4 alkyl group,N is 0 or 1,R.sup.2, r.sup.3, r.sup.4 and R.sup.5 are independently hydrogen or an .alpha.- or .beta.-hydroxyl group, or an oxo group,H.sup.5 is an .alpha.- or .beta.-H.The subject compounds, particularly the gamma emitting isotopes, are useful in the investigation of body functions.

Abstract: Folic acid and related compounds are assayed by competitive radio-assay using a selenium - 75 labelled version of folic acid as the competing compound.

Abstract: Novel selenium derivatives of steroids have the formula I, ##STR1## where X is hydrogen or acyl, Y is hydrocarbon and n is 0 or 1, preferably 0. Such compounds, labelled with selenium-75 are of use for investigating body function, particularly for imaging the adrenal glands, and are claimed superior for the purpose to the 6.beta.- and 19- iodine derivatives of cholesterol.

Abstract: New selenium-75 labelled derivatives of cyclic nucleotides are described, which are of value in the saturation analysis of cyclic nucleotides, particularly adenosine-3', 5'-cyclic monophosphate (cyclic AMP) in body fluids.

Abstract: The invention provides a method and a kit for the saturation analysis of a steroid characterized by the use of a selenium-75 labelled version of the steroid to be assayed. Selenium-75 derivatives of steroids are quite simple to prepare and have practical advantages over other radioactively labelled steroids. Lists of derivatives and examples of competitive radio-assays are given.

Abstract: Novel selenium-75 derivatives of cholesterol have the formula ##STR1## (I) where X is hydrogen or acyl, Y is alkyl and n is 0 or 1. They are useful for visualizing the adrenal glands of mammals.