Dynamic mechanical properties of human brain tissue

Investigators have been studying the mechanical phenomena associated with impact to the head for many years. Several theories on the behavior of the brain during head impact have come from these studies but there has been a notable lack of information on the bulk mechanical properties of the brain which are necessary for the evaluation of these theories. This paper represents an initial attempt at providing such information.The dynamic complex shear modulus of in vitro samples of human brain have been measured. Specimens from eight brains have been subjected to a sinusoidal shear stress input under resonant conditions in an electro-mechanical test device. Tests were conducted to determine the effects of time after death, refrigeration of material and shear strain dependence. A device to measure the dynamic properties of brain in vivo is described and preliminary data on in vivo tests on Rhesus monkeys is presented.The results of the dynamic shear testing on in vitro human brain indicate that the storage modulus G' lies between 6-11 x 103 dyn/cm2, the loss modulus G" lies between 3[middle dot]5-6[middle dot]0 x 103 dyn/cm2 and the loss tangent tan [delta] is in the range 0[middle dot]40-0[middle dot]55.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32936/1/0000319.pd

Opportunities for Lipid-Based Probes in the Field of Immunology

Lipids perform a wide range of functions inside the cell, ranging from structural building block of membranes and energy storage to cell signaling. The mode of action of many signaling lipids has remained elusive due to their low abundance, high lipophilicity, and inherent instability. Various chemical biology approaches, such as photoaffinity or activity-based protein profiling methods, have been employed to shed light on the biological role of lipids and the lipid-protein interaction profile. In this review, we will summarize the recent developments in the field of chemical probes to study lipid biology, especially in immunology, and indicate potential avenues for future research.Molecular Physiolog