Mechanical properties of soft human tissues under dynamic loading.

The dynamic response of soft human tissues in hydrostatic compression and simple shear is studied using the Kolsky bar technique. We have made modifications to the technique that allow loading of a soft tissue specimen in hydrostatic compression or simple shear. The dynamic response of human tissues (from stomach, heart, liver, and lung of cadavers) is obtained, and analyzed to provide measures of dynamic bulk modulus and shear response for each tissue type. The dynamic bulk response of these tissues is easily described by a linear fit for the bulk modulus in this pressure range, whereas the dynamic shearing response of these tissues is strongly non-linear, showing a near exponential growth of the shear stress.

Characterization of the effect of cocaine on catecholamine uptake by pregnant myometrium.

OBJECTIVE: To characterize the effect of cocaine on catecholamine uptake by myometrium from pregnant women. METHODS: Slices of myometrium obtained from nine women during elective cesarean delivery at term were incubated with [3H]-norepinephrine and various uptake inhibitors for 30 minutes. The radiolabeled material was extracted with perchloric acid, expressed as percent control (+/- standard error of the mean), and compared by one-factor analysis of variance and Fisher multiple range test. RESULTS: Myometrial uptake was inhibited by cocaine (42 +/- 9%) by neuronal (type 1) uptake inhibitors (desipramine 41 +/- 14%; N-ethylmaleimide 53 +/- 8%), and by extraneuronal (type 2) inhibitors (normetanephrine 56 +/- 19%; corticosterone 73 +/- 9%). When uptake inhibitors were used in combination with cocaine, uptake was not decreased further in the presence of neuronal inhibitors (desipramine plus cocaine 40 +/- 20%; N-ethylmaleimide plus cocaine 42 +/- 4%). However, the effect of cocaine appeared to be added to that of extraneuronal inhibitors (normetanephrine plus cocaine 25 +/- 14%; corticosterone plus cocaine 32 +/- 1%). CONCLUSION: Catecholamine uptake by myometrium in pregnant women appears to be both extraneuronal and neuronal in nature, and cocaine inhibits the neuronal portion of this uptake. This mechanism may play a role in the increased rate of premature delivery associated with cocaine abuse.