Hair pulling is a neuroimmunological condition

TRICHOTILLOMANIA (or hair pulling) is a condition characterised by excessive grooming and strong, repeated urges pull out one’s own hair. It is classified as an obsessive-compulsive disorder (OCD), and is relatively common, affecting about 2 in 100 people. Sufferers normally feel an increasing sense of tension before pulling out their scalp hair, facial hair, and even pubic hair, eyelashes or eyebrows. This provides gratification, but only briefly.

Hair pulling is usually thought of as being psychological in origin, but an intruiging new study now suggests that it occurs as a result of defects in the immune system. The study, which is published in the journal Neuron, shows that excessive grooming and hair pulling occur in mice because of reduced numbers of microglial cells, which are critical  for the brain’s immune response. It also suggests – very unexpectedly – that bone marrow transplants may be an effective treatment for trichotillomania in humans.

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‘Wasabi receptor’ is snake’s infrared sensor

SNAKES have a unique sensory system for detecting infrared radiation, with which they can visualize temperature changes within their immediate environment. Using this special sense, they can image the body heat radiating from warm-blooded animals nearby. This enables them to track their prey quickly and with great accuracy, even in the dark, and to target the most vulnerable parts of the prey’s body when they strike. It also warns them of the presence of predators, and may be used to find appropriate locations for building dens.

Infrared detection is known to be mediated by a specialized sensory apparatus called the pit organ, but several important questions about the detection mechanisms remain. It is still unclear, for example, where in the pit organ the infrared sensor is located, and whether it detects light particles directly, in a similar way to the eye, or heat energy. These questions have now been answered by a group of researchers from the University of California in San Francisco. In an advance online publication in the journal Nature, they report the identification of the sensor: it is an ancient protein called TRPA1, which has been adapted for this purpose in snakes, but not in other vertebrates.

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