Death in the Blink of an Iris

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Science  04 Nov 2005:
Vol. 310, Issue 5749, pp. 747-749
DOI: 10.1126/science.310.5749.747d

In early development, the eye is covered with a membrane that includes blood vessels and that functions to nourish the developing lens and retina. This membrane, however, obscures the clear optical path needed for visual acuity.

Studying rats, in which the eye matures postnatally, Morizane et al. uncover the link between maturation of the iris and the apoptosis of blood vessels supplying the immature eye. A key moment is when the iris begins to move, constricting and dilating in the way that will later control the light supply to the lens and improve focus. The constricting movements place pressure on the persistent blood vessels, causing the blood supply to stop intermittently. Pharmacologic intervention that paralyzed iris movements delayed regression of the vascular membrane. The authors propose that it is the increasing intermittency of the blood flow, rather than the mechanical shear stress induced by iris movement, that signals cells of this vascular membrane to initiate apoptosis. — PJH

Am. J. Physiol. Regul. Integr. Comp. Physiol. 10.1152/ajpregu.00602.2005 (2005).

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