No abstract

SYNOPSIS As a possible more rapid test of lymphocyte reactivity to phytohaemagglutinin (PHA) than the standard estimation of thymidine uptake after 72 hours (T72), uridine uptake after 24 hours (U24) was studied in a total of 96 individuals. No reliable correlation between the two estimations was found in 29 outpatients showing a wide range of reactivity to PHA nor in 30 healthy control subjects nor in 16 pregnant subjects.Conflicting reports have appeared in the literature as to whether lymphocyte reactivity to PHA is normal, depressed or enhanced in pregnancy. Our group of pregnant subjects showed a significant depression of both U24 (p < 0.01) and T72 (p < 0-02) results as compared to normal female controls.Cultures of semipurified lymphocytes prepared by gradient centrifugation on a further 21 normal control subjects showed no better correlation between U24 and T72 results than the above unpurifiedleucocyte cultures.

l‐threo‐phenylserine and esters of threo‐phenylserine were the most active of a series of compounds tested against influenza A virus in tissue culture. Substitution of the β‐OH or α‐NH2 group abolished activity. The activity of phenylserine was reversed competitively by phenylalanine. Phenylserine did not act on free virus or on the adsorption of virus to host cells. It prevented virus growth if added during the first half of the latent period. Phenylalanine appears to be necessary for virus synthesis and can be supplied by phenylalanylglycine or glycylphenylalanine. Phenylserine had no significant activity against ectromelia infections in mice, even when the amino acid content of the livers had been depleted by starvation.

As part of a programme of investigations into the chemotherapy of virus infections, Rous sarcoma I virus has been used as one of our test viruses. This paper reports the techniques employed and the results for various substances including some known to be effective in the treatment of tumours, e.g. the nitrogen mustards, triethylene melamine, and colchicine. References to these cytotoxic agents appear in recent articles by Loveless and Revell (1949) and Rose, Hendry, and Walpole (1950), and will not bv given here. Other compounds were tested because of their action on bacteriophage, e.g. R.D. 347=4: 4'-bis-(2-dihydroglyoxalinyl) stilbene dihydrochloride monohydrate, and R.D. 1367=2: 7-bis-(2-dihydroglyoxalinyl)-9phenyl-phenanthridine trihydrochloride dihydrate (Dickinson and Codd, 1952), and malabar kino (Chantrill, Coulthard, Dickinson, Inkley, Morris, and Pyle, 1952). Rous sarcoma virus had been grown in fertile eggs by Murphy and Rous (1912) and Keogh (1938), and in day-old chicks by Duran-Reynals (1940); for reasons of convenience in housing animals and in the amount of drug required for treatment attention was therefore directed to the use of these hosts for testing purposes. EXPERIMENTAL METHODSStrains.-The Rous sarcoma I virus was originally obtained as a freeze-dried tumour specimen from Dr. F. R. Selbie. It was passaged three times intramuscularly in fowls and once on the chorioallantoic membrane of fertile eggs. Egg membrane material was ground in broth and, after centrifugation, the supernatant fluid was filtered through a gradocol membrane of pore size 1.23 /A. This filtrate was the starting point for the work reported here.Preparation of inocula and maintenance of stocks.-Egg membrane material was passaged 10 times on the chorioallantoic membrane of fertile eggs, 10-day embryos being used and incubation being maintained for a further 7-9 days after inoculation of the virus. Neither whole nor ground membranes maintained their titre for more than one month at -20' when kept in 5 per cent glucose broth and stocks were therefore kept at -70' or freeze-dried. It was later found that the livers of chicks dying from a generalized infection after the intraperitoneal inoculation of day-old chicks were much more satisfactory, for stock preparations, than either membranes or fowl tumours. Such livers were always bacteriologically sterile, were very easy to grind into uniform suspensions, and gave rise to high titre material which maintained its titre indefinitely at -70' or when freeze-dried and for at least one month at -200. For stocks, one liver was