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Ambrose et al. propose a likely scheme for the course of tumour development, as a failure of the host immune system.

PACKED potato starch, which has been widely used for zone electrophoresis, offers certain advantages when employed as a supporting medium in the ultracentrifuge. Boundaries are stabilized, making recovery of fractions easier, and the proteins thus far studied sediment at least twice as rapidly in starch as in free solution. This has been shown in experiments with rat haemoglobin (1 per cent) or bovine serum albumin (1–5 per cent) stained with bromphenol blue centrifuged in starch and in free solution under identical conditions. Centrifugation was done in the ‘Spinco’ Model L centrifuge by use of an SW 391 swinging-bucket rotor at approximately 20°. A 0.1 ionic strength pH 7.5 phosphate–sodium chloride buffer was used in each instance. The ‘Lusteroid’ centrifuge tubes were completely filled with a slurry of starch–protein mixture and accelerated briefly to 20,000 r.p.m. After deceleration, excess fluid was removed and more starch slurry added. The packing procedure was repeated a second time and excess fluid again removed. It is important that the starch suspensions be freshly made, since part of the starch appears to dissolve slowly with time, destroying the effect observed here.

VIRAL material used to prepare inactivated virus vaccines must be concentrated to provide sufficient antigenic mass to stimulate the vaccine's protective mechanisms, and purified to remove nonviral host material which may cause side reactions and sensitization to host (for example, egg) components. A continuous-flow zonal centrifuge, the K-II-B1,2, has been designed for use in large scale production of influenza vaccines. We have grown influenza virus in tissue culture and have concentrated and purified it in a single step process using this centrifuge.

VIRUS infection is widespread throughout the animal and plant kingdoms, and produces most human illness1, possibly including certain types of cancer2. Particles with viral morphology are easily isolated from sea3 or river water suggesting that they are ubiquitous. In this communication we have assembled evidence to support the view that viral transduction is a key mechanism for transporting segments of DNA across species and phylum barriers, and that evolution depends largely on this transfer. The evidence may be summarized as follows.

IMMUNIZATION of adult hamsters with irradiated foetal hamster or mouse cells produces strong immunity to SV40 cell challenge and simultaneously induces cytostatic (or C) antibody formation1. Furthermore, adenovirus 31 tumorigenesis can be interrupted by a single injection of hamster foetal cells if administered to neonatally infected hamsters 3 weeks after birth and before the appearance of the tumour2. SV40 viral oncogenesis could be similarly interrupted in male but not female hamsters2. This work provides support for the view that foetal and tumour cells share common antigens and that oncogenesis involves retrogenic activation of early foetal antigen genes in adult cells3,4.

THE improvement of methods for isolating cell nuclei requires the establishment of suitable criteria of nuclear intactness which may be used to evaluate changes in technique1. The following experiments were performed in the course of an effort to devise methods for following changes in the degree of polymerization of deoxyribonucleic acid during nuclear isolation.