Strains of M. tuberculosis during infection

2008 meeting - Biochemical signals maketh man

Physiologists have known for more than a century that an intricate system of biochemical communication in the blood stream makes organs respond to environmental inputs. In the last three decades, biomedical science has uncovered possibly thousands of signalling networks. These integrate every one of the mammalian body's ten trillion cells into an organisation that facilitates a unified response to any objective the brain might conceive and play spectacular roles in organising the development of the body from a fertilised egg.

To visualise the importance of cell-to-cell signalling, imagine each cell as receiving signals through a mobile phone, and then imagine each cell receiving and transmitting perhaps a hundred or a thousand messages simultaneously with a different ring tone for each one. It sounds like a recipe for chaos but cells have acquired the organisation during evolution of how to deal with such complicated communications.

The presentations concerned just two examples that illustrate the subtlety and distinctiveness of such processes.

Making the spinal cord - Dr James Briscoe

James Briscoe has been awarded the EMBO Gold Medal in 2008 for his work on a molecule that has the endearing name of "sonic hedgehog". This secreted protein plays an important part in organising the tissues of the spinal cord as it forms. The prospective spinal cord of vertebrates is formed from a sheet of cells on the surface of the embryo that folds up into a tubular structure known as the neural tube. Sonic hedgehog is made by a tissue that underlies the neural tube and is released into the spaces between the cells. It diffuses away from the source becoming more dilute further from the source.

The cells of the neural tube are "instructed" by this "signal" to take on a specific identity depending on the concentration they detect. The identities they assume are different kinds of neurones. Cells close to the source will become motor neurons that control muscles while cells at the extreme top of the neural tube will become migratory cells (the neural crest) that form many kinds of tissues elsewhere in the body, including endocrine organs. We hope investigations of this kind will shed light on diseases where the embryonic development of the spinal cord is disrupted, such as spina bifida and these studies might also help in the development of applied and therapeutic uses of stem cells.

Regulating the hormone that makes bones grow - Professor Iain Robinson

Growth hormone is a classical example of an endocrine secretion. It is produced by the anterior pituitary gland and regulates the growth of the long bones and metabolic responses in many different target tissues. Release of growth hormone is controlled by a part of the brain, known as the hypothalamus that tells the pituitary to secrete hormone in several large pulses each day using biochemical messengers. Exactly why the hormone is released in this mysterious fashion is a great puzzle. Another mystery is; how do the secreting cells act in concert when they seem to be present in the anterior pituitary gland as isolated individuals.

New microscopic techniques have revealed that the cells are connected in a network that facilitates coordinated secretion. Some children born with impaired growth clearly lack functioning growth hormone. These children are usually treated with growth hormone made by gene technology in cellular factories (eg bacteria). In order to achieve a proper growth response, the growth hormone must be delivered in a pulsatile fashion using special infuser that injects the hormone several times a day. There is some evidence that levels of growth hormone decline in old age but properly conducted research indicates that there are no benefits of replacement therapy in old age although the internet abounds with claims to the contrary.

 

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