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This programme examines some work by scientists engaged on research into hormonal mechanisms in insects. The programme is in two parts. The speakers are Dr. R.I. Holmes, Lecturer in Biology at the ...Open University, Professor Sir Vincent B. Wigglesworth, P.U.S., and Dr. Simon Maddrell, Fellow of Gonville and Caius, Cambridge. In the first part of the programme the classic experiments on the control of moulting and metamorphosis in the bug Rhodnius are demonstrated. Sir Vincent Wigglesworth gives the historical background to his pioneer work on the hormonal control of these processes in Rhodnius. Dr. Holmes demonstrates the experimental techniques used by Sir Vincent in this work with living Rhodnius and diagrams. In the second part of the programme Dr. Maddrell demonstiates some of the techniques by which he has investigated the control of the onset of diuresis in Rhodnius. An isolated Malpighian tubule preparation is used to demonstrate the presence of diuretic hormone in the haemolymph and together with ligature experiments used to locate the site of hormone production. This is shown to be from neurosecretory cells in the mesothoracic ganglion and an extract of these cells is shown to produce a diuresis in the isolated malpighian tubule preparation.
Metadata describing this Open University video programme
Item code: S22-; 09
Series: Comparative physiology
Episode 9
First transmission date: 20-05-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:23:27
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Producer: Tony Laryea
Contributors: Richard Holmes; Simon Maddrell; Vincent Wigglesworth
Publisher: BBC Open University
Keyword(s): Diagrams; Haemolymph; Hormonal mechanisms; Insects; Ligature experiments; Malpighian tubule preparation; Metamorphosis; Moulting; Neurosecretory cells; Rhodnius
Footage description: Richard Holmes introduces the programme by describing how the bug Rhodnius prolixus passes through five larval stages before metaphorphosing into a winged adult. Shots of Rhodnius in its various larval stages. Sir Vincent Wigglesworth gives the historical background to his pioneer work on moulting and metamorphosis. Richard Holmes explains and demonstrates the techniques used by Wigglesworth in his research. Shots of pairs of Rhodnius larvae in parabiosis. Holmes explains how this is done. Sir Vincent Wigglesworth continues his discussion. He refers to the work of Kopec on the gypsy moth and on neurosecretory cells in invertebrates by Hanstrom and Scharrer which helped put him on the right track. Richard Holmes sums up the present knowledge of the moulting and metamorphosing processes in Rhodnius. He uses diagrams to show how Wrigglesworth arrived at his conclusions - that a brain hormone acts on the prothoracic glands which release ecdysone hormone into the blood. It is this hormone which causes moulting. The corpora allata secrete a "juvenile hormone" which prevents metamorphosis until the final moulting stage. Vincent Wrigglesworth continues his discussion on the factors which regulate metamorphosis. Richard Holmes continues to sum up Wrigglesworth's work using models and diagrams to aid his discussion. Dr. Simon Madrell explains and demonstrates his technique for investigating the rapid fluid excretion (urine) in Rhodnius after a blood meal. Shots of Rhodnius taking a blood meal and urinating a few minutes later. Madrell shows a preparation of single Malpighian tubes which respond to "diuretic hormone" in the haemolymph . Madrell "ligatures" Rhodnius bugs at different levels and collects the fluid discharged from their guts on sensitive papers. This experiment shows that some structures in the mesothoracic neurosecretory cells from the mesothoracic ganlion produce diuresis in isolated Malpighian tubules even when diluted by a factor of 10. Richard Holmes discusses the sensory stimuli involved in the moulting process in this case the stretching stimulus after a blood meal which causes the release of hormones.
Master spool number: 6HT/70510
Production number: 00521_3101
Videofinder number: 3583
Available to public: no