| Citation | Follett is specially distinguished for his work on the regulation of reproduction in birds by seasonal changes in daylength (photoperiodism) and he directs an ARC Group working on this topic. He has developed the Japanese quail (Coturnix coturnix) as a model species for these studies and has investigated inter alia the nature of the biological 'clock' underlying photoperiodic time measurement, its histological basis in the neuroendocrine circuitry within the brain and the patterns of gonadotrophic secretion and gonad development which the 'clock' controls. He has shown that circadian rhythms are involved in day-length measurement and has delineated the hypothalamic areas involved in photoinduction. These studies have been supplemented by investigating the circulating levels of gonadotrophins and prolactin in normal birds under differing light regimes and after sophisticated experimental treatments. Measurements of circulating hormones have been made by avian radioimmunoassays developed de novo by Follett and his associates. In earlier work on the control of vitellogenesis in Xenopus laevis Follett was a pioneer in demonstrating the role of oestrogens in stimulating specific protein (vitellogenin) synthesis by the liver. He also isolated and partially characterised Xenopus vitellogenin and established a specific radioimmunoassay for studying the physiology of vitellogenesis. |