Occurrence of substance P, vasoactive intestinal peptide and calcitonin gene-related peptide in dermographism and cold urticaria.

Substance P (SP), calcitonin gene-related peptide (CGRP), and vasoactive intestinal peptide (VIP) were assayed in lesions and normal skin of patients with dermographism and cold urticaria utilizing suction-induced blisters. There was no difference in SP and VIP concentrations between challenged and control skin of urticaria patients. On the whole, however, the concentration of both neuropeptides, and VIP in particular, was higher in the urticaria patients than in control subjects. CGRP levels were not increased. SP and VIP in blood samples from veins draining challenged skin areas were below the detection limit. It is concluded that SP and VIP may potentiate histamine in wheal formation and thus contribute to the increased reactivity of the skin to trauma and temperature changes in patients with physical urticaria

Physical virology

Viruses are nanosized, genome-filled protein containers with remarkable thermodynamic and mechanical properties. They form by spontaneous self-assembly inside the crowded, heterogeneous cytoplasm of infected cells. Self-assembly of viruses seems to obey the principles of thermodynamically reversible self-assembly but assembled shells ('capsids') strongly resist disassembly. Following assembly, some viral shells pass through a sequence of coordinated maturation steps that progressively strengthen the capsid. Nanoindentation measurements by atomic force microscopy enable tests of the strength of individual viral capsids. They show that concepts borrowed from macroscopic materials science are surprisingly relevant to viral shells. For example, viral shells exhibit 'materials fatigue- and the theory of thin-shell elasticity can account - in part - for atomic-force-microscopy-measured force-deformation curves. Viral shells have effective Young's moduli ranging from that of polyethylene to that of plexiglas. Some of them can withstand internal osmotic pressures that are tens of atmospheres. Comparisons with thin-shell theory also shed light on nonlinear irreversible processes such as plastic deformation and failure. Finally, atomic force microscopy experiments can quantify the mechanical effects of genome encapsidation and capsid protein mutations on viral shells, providing virological insight and suggesting new biotechnological applications. © 2010 Macmillan Publishers Limited. All rights reserved