The three hundred occupants of the Babraham Institute conduct their biomedical research in surroundings that are a little out of the ordinary: a 19th century stately home in a small village just to the south of Cambridge. There I met Paul Cuddon, a final year PhD student who is completing his studies under Dr Martin Bootman at the world-renowned Laboratory of Molecular Signalling. With the help of Dr Simon Walker, the group's imaging specialist, Cuddon has taken photographs of neurons at the extraordinary level of detail seen on the front cover. These images allowed him to visualise the fine level of interaction between two of the principal cell types of the brain, the neuron and the astrocyte.

As Cuddon explained to me, the photograph featured on the front cover shows neurons in green, and their nuclei - just 10 micrometres in diameter - in blue. The neurons communicate with each other both via tiny fibres called neurites and larger, one micrometre diameter axons that lead away from the cell nucleus. The red wool-like structures seen in the photograph are astrocytes, supportive cells that provide neurons with vital nutrients and oversee the formation of neuron-neuron connections.

Cuddon has been examining the role of calcium ions in the development of hippocampal neurons, which are necessary for learning and memory consolidation in the brain. Calcium is essential for the normal function of a wealth of bodily processes, including muscle contraction, bone structure, fertilisation, and cell communication. It is not surprising then, that these ions also play a critical part in neuronal development by controlling the physical growth of embryonic cells.

However, measuring ionic fluctuations in intact brains is not easy. So instead, Cuddon cultured neurons on glass coverslips at low and high densities, both with and without the supporting astrocytes. Such models of the brain then allowed him to compare the development of neuronal networks with neurons grown in isolation. Mature high density cultures best represent the brain cells' native environment, and after two weeks, the cultured cells begin to exhibit synchronised oscillations of intracellular calcium. Cuddon monitored these changes by applying a calcium sensitive dye, which makes changes in intracellular calcium visible under a microscope.

So how were his impressive photographs created? Cuddon explains that neurons and astrocytes were labelled with different primary antibodies, via a technique known as immunofluorescence. Each antibody binds only to a specific protein expressed by a given type of cell, or part of a cell, such as the nucleus. The neurons are then washed with different fluorescently tagged, secondary antibodies that bind uniquely to each primary antibody. Finally, the cells were illuminated with three different colours from a laser. Since each secondary antibody only emits light at a distinct wavelength, one is able to image a specific type of cell, or part of a cell, with each of the three laser colours. A state-of-the-art computer combines the separate red, green and blue images to produce a photograph of the astrocytes, neurons and nuclei, which appear in red, green and blue respectively. It is even possible to focus the lasers at different depths through the cells, letting Cuddon and Walker build up three-dimensional movies of the neurons.

Cuddon's photographs allow him to determine the exact densities of neurons and astrocytes on each glass coverslip. This has led to a number of important discoveries. Most significantly, the longer the high density neurons were kept in culture, the more advanced their calcium signalling pathways became. Although the lower density neurons survived damaging prolonged stimulation better than their high density counterparts of the same age, they did not develop the same normal intracellular signalling machinery. This means that a high density is essential for a new neuron to develop correctly. The red wool is also important: the astrocytes helped the low density neurons to live longer and maintained the health of the adult neurons.

Once Cuddon's work is published, he will leave the Babraham to move to the Cambridge Institute for Medical Research, where he hopes to carry out more clinical research into therapies for neurodegenerative diseases, such as Alzheimer's, Huntington's and Parkinson's. It is in this that Cuddon's current research into the role of calcium ions in the development of hippocampal neurons may prove vital. Perhaps, by manipulating neuronal development, treatment for these so far incurable diseases may even become possible!

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Jonathan Zwart is a PhD student in the Cavendish Laboratory