The Department of Biomedicine

BBB seminar: Johan Hermanus Koeslag

3D: Daisies, Dextrose and Diabetes

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Johan Hermanus Koeslag
Professor and Head of the Department of Medical Physiology and Biochemistry, University of Stellenbosch, Tygerberg, South Africa

The Daisyworld Parable describes an imaginary planet orbiting a variable star. It is populated only by black and white daisies, both of which grow best at 22.5°C. Remarkably, this leads to very precise temperature homeostasis on Daisyworld. Exact analogies exist for the insulin-glucagon counterregulatory pair of hormones in glucose homeostasis, and for the calcitonin-PTH pair in plasma calcium homeostasis, provided the latter pair of hormones are co-secreted with a common inhibitory chromogranin. The insulin-glucagon pair can be backed up by growth hormone, if 'co-secreted' somatostatin inhibits both sets of regulators. Disruption of the latter system by amyloid deposition in the pancreatic islets causes all the symptoms of type 2 diabetes mellitus.


Professor Johan Hermanus Koeslag, originally Dutch, has been living in Indonesia and in several African countries. He obtained his medical training at the University of Cape Town and after internships in General Medicine, Surgery, Obstetrics and Gynaecology started his scientific career at the Department of Physiology at the University of Cape Town. Since 1990 he holds the position of Head of the Department of Medical Physiology and Biochemistry at the University of Stellenbosch, South Africa.

Dr. Johan Koeslag's main research interests are the molecular aspects and hormonal regulation of the glucose homeostasis. He is known to be an excellent and inspiring lecturer