Renewal of the mineral constituents of the skeleton

i

iodine-132. I n their technique, iodine-132 accumulates as iodate t h r o u g h the radioactive decay of tellurium-132 in a n acid p e r m a n g a n a t e solution. W h e n required for use, the iodate is reduced to iodine a n d distilled off. T h e residual solution is then reoxidized with p e r m a n g a n a t e so t h a t fresh 1132 will continue to a c c u m u l a t e as iodate. F u r t h e r reduction is therefore required in order to o b t a i n a further supply. W h e n frequent use is to be m a d e of such a source, a n d especially w h e n the exact times at w h i c h it will be w a n t e d are not accurately k n o w n in advance, this procedure is inconvenient. This is the more so, since the p r o d u c t has a half-life of only 2.4 hours. W e h a v e found that, u n d e r suitable conditions, the source c a n be kept p e r m a n e n t l y reduced so t h a t the 1132 accumulates as iodine a n d is readily volatile in a current of air. T h e a p p a r a t u s used is shown in the d i a g r a m , a n d consists of a 250-ml flask s u r r o u n d e d b y a heating element. A delivery-tube reaches to the b o t t o m of the flask t h r o u g h which the source, in dilute sulphuric a n d phosphoric acids, is sucked into the generating flask; the m e t h o d used will be obvious from the diagram. 0.1 ml of a 40% solution of h y d r o x y l a m i n e sulphate is then sucked in to effect reduction, while leaving a large excess of reducing agent. Most of the w a t e r is then distilled off, together with a first yield of 1132, leaving a strongly-acid source containing only a little water. T h e t e m p e r a t u r e of the flask is t h e n allowed to fall to a b o u t 60°C, at which it is m a i n tained. U n d e r these conditions the source e m a n a t e s 1132 continuously as molecular iodine, m u c h of which accumulates in the air-space above the liquid. All t h a t is necessary to procure a supply is to d r a w a current of air t h r o u g h tile source. T h e agitation p r o d u c e d by the b u b b l i n g disengages further I 1~2 from the solution. T h e 1132 v a p o u r is t r a p p e d as iodide in N / 1 0 0 sodium sulphite solution a n d is then ready for use. T h e reduction of iodine to iodide b y h y d r o x y l a m i n e is rapid in neutral solution, a n d is far from negligible even in strongly-acid solutions at a t e m p e r a t u r e of 60 °. This would result in immobilization of p a r t of the 1132 within the generating flask. C o o k et al. h a v e pointed out t h a t this reaction m a y be suppressed by the addition of h y d r o g e n peroxide. O u r practice is to suck in 0.5 ml of 20-vol h y d r o g e n peroxide at a n y time w h e n the yield shows signs of falling below w h a t it should be, or of being difficult to disengage from the flask. I t is unnecessary to e m p t y the flask before the next delivery of tellurium is added. W e h a v e not dism a n t l e d our e q u i p m e n t for several months, d u r i n g

R e n e w a l o f the M i n e r a l C o n s t i t u e n t s of the S k e l e t o n Received 2 November 1956) THE first application of artificial radioactive isotopes in biological studies was the investigation if a n d to w h a t extent the phosphorus atoms of the b o n e apatite of the fully g r o w n r a t are renewed. I n the course of 24 hours a b o u t 3 0 % of the phosphorus atoms were f o u n d to be replaced by labelled atoms. I n view of the comparatively short life of p32 the application of this radioactive tracer does not p e r m i t to follow the r e p l a c e m e n t of the m i n e r a l constituents of the skeleton d u r i n g life. W h e n , later on, Ca 4~ with 5"1/2 = 152 days was available, it was possible to follow the extent of r e p l a c e m e n t of the Ca atoms of the skeleton t h r o u g h the lifetime of the mouse. Ca t5 was administered to p r e g n a n t mice a n d to the offspring while they were growing, o b t a i n i n g thus uniformly labelled o u t g r o w n animals. T h e Ca 45 c o n t e n t of the skeleton of a m e m b e r of each litter was t h e n determined. T h e other m e m b e r s were placed on a non-radioactive diet a n d killed at intervals w i t h i n over 1 year. After the lapse of this time, which is a very large p a r t of the lifetime of the mouse, out of the labelled calcium atoms present in the skeleton of the o u t g r o w n mice 67.2 ~z 7"9% were found still to be present in the skeleton of sister mice. W h e n a d m i n i s t r a t i o n of Ca 45 was i n t e r r u p t e d after the b i r t h of the litter a n d its members, reared b y inactive mothers, were sacrificed at different dates w i t h i n 560 days, h a l f of the calcium atoms present at b i r t h were found to b e preserved d u r i n g the lifetime of the mouse. F r o m the figures o b t a i n e d for the passage of labelled calcium from one g e n e r a t i o n to the next, it follows t h a t the eleventh generation no longer contains a single calcium a t o m of those present in the first generation of its ancestors. G. HEvEs'z Institutest fiir organisk kemi och biokemi 18 N. ~liilarstrand Stockholm, Sweden

An Emanating

S o u r c e for 1132

(Received 5 December 1956) COOK, EAKaNS, a n d VEALL h a v e described 11) the l a b o r a t o r y p r e p a r a t i o n a n d clinical usefulness of 85