152 TOXICOLOGY

Green, C. R. & Christie, G. S. (1961). Malforma- tions in foetal rats induced by the pyrrolizidine alkaloid, heliotrine. Brit. J. exp. Path. 42, 369.

187. TERATOGENIC ACTIVITY OF PURIFIED TRYPAN BLUE

Commercial samples of Trypan Blue show wide variations in their teratogenic activities (Beck, J. EmbryoL exp. Morph. 1961, 9, 673) and so there is some uncertainty whether the activity derives from the blue colouring or any impurities. The authors therefore prepared by chromatographic separation, a sample of the blue colouring which contained only a faint trace of purple but no red compounds, and compared its activity with that of an unpurified portion of the commercial colouring sample. A single dose, 50 mg/kg of colouring was injected into pregnant rats. At post mortem the percentage of rats in the 2 groups showing implantation sites, resorp- tions or abnormal foetuses were not significantly different. The activity therefore was due to the main blue colour component and variations between different samples might be due to the presence of different amounts of this component. Lloyd, J. B. & Beck, F. (1962). The teratogenic activity of purified samples of trypan blue. Biochem. J. 83, 30.

188. TERATOGENESIS IN GUINEA-PIGS The guinea-pig has been little used in teratogenic

studies despite the advantages it possesses namely: readily identifiable oestrus and ovulation periods and a longer gestation period than any other small laboratory mammal with identifiable trimesters not unlike those in human females save for length. A study is reported of the effectiveness of Trypan Blue injections in producing malformations, the influence of the timing of such injections, whether congenital malformations are present in viable young at term, and of the length of time over which tissue differenti- ation extends in the guinea-pig. A dose of 2 ml of 1% Trypan Blue given subcutaneously was selected for use as it produced in guinea-pig embryos a high proportion of abnormalities and a low incidence of resorption of the embryos. When females were treated with Trypan Blue between the 6th and 13th days of gestation and embryos recovered on the 30th day, reduction of growth was found in 43 % and abnormalities in over 50%. Abnormalities included cyst of the anterior thoracic wall, spina bifida, microphthalmia, hydrocephaly, oedema and menin- gocoel.

As regards timing, resorptions and malformations occurred when Trypan Blue was given between the 9th and 13th day of gestation with a maximum on the I l th day. Treated females gave rise to litters of less than normal size; abnormalities compatible with life were present in 5 % of offspring. In both rats and guinea-pigs implantation occurs on the 8th day of gestation, but in these 2 species injections of Trypan Blue produce maximum teratogenic effects on the 8th and 11th days respectively. After the 1 l th day in

the rat, Trypan Blue no longer produces teratogenic effects (Wilson et al. Anat. Rec. 1959, 133, 115). It was not found possible to determine from the present study the length of the critical period in guinea-pigs.

Hoar, R. M. & Salem, A. J. (1961). Time of terato- genic action of trypan blue in guinea-pigs. Anat. Rec. 141, 173.

189. A NEW SULPHYDRYL-BINDING AGENT ?

Sterculic acid (DL-cis-2-octyl-l-cyclopropene-1- octanoic acid) is an interesting chemical and bio- logical curiosity, an oleic acid in which the double bond forms part of a cyclopropene ring. It is derived from the seedfat of the tropic tree Sterculia foetida and is notable for the fact that its ingestion by hens causes the eggs to turn pink on storage, with an accompanying abnormally rapid increase in pH.

A report from the 141st National Meeting of the American Chemical Society reveals the following effects of sterculic acid and related compounds; em- bryonic mortality increases and af ter hatching, development and egg production are retarded, with concomitant changes, both pathological (liver and

• gall-bladder enlargement) and biochemical (de- creased iodine number of body fat).

How are these effects brought about? It is suggested that sulphydryl groups of proteins become bound to the cyclopropene ring. Model experiments with 2 cyclopropene derivatives, sterculene and methyl sterculate reveal ready addition to methyl mercaptan and fl-mercaptopropionic acid. Oleic acid fails to react under similar conditions.

Amer. chem. Soc. 141st Nat. Meeting. (1962). Cycloprene of Sterulic compounds is active. Chem. Eng. News 40 (14), 61.

190. EFFECT OF THALIDOMIDE ON THE GROWTH OF COCKERELS

Thalidomide (I) was introduced in 1956 for use as a sedative and hypnotic after toxicological studies of over a year's duration had been carried out in several species of animals (Somers, Brit. J. Pharmacol. 1960, 15, 111). The present investigation was prompted by certain observations made during work carried out on another aspect of the action of I in pullets and cockerels. Cockerels of 7-8 weeks were given orally 250 mg I/kg dally until the 32nd day and thereafter 500 mg/kg daily until the 56th day. Post-mortem examinations were undertaken on the 33rd and 57th days. A significantly reduced rate of weight gain was seen that was not due to a decreased consumption of food. The most obvious effect of I however was retardation of development of the secondary sexual characteristics; delay in spermato- genesis was also demonstrated. No abnormality was seen in any other endocrine gland.

The author considers that the effects of I on growth and sexual development may have been due to the production by I of a folic acid deficiency. In