A preliminary study on the rheological properties of human ejaculate and changes during liquefaction.

AIM: To study the changes in rheological properties, namely the parameters of the hysteresis loops and yield stress versus time for human semen after ejaculation. METHODS: Ejaculates were obtained from volunteers and immediately put into the test cup of a Brookfield Programmable DV-11 Rheometer, by which the hysteresis loops and yield stress were determined. RESULTS: (1) Yield stress values dropped down from more than 3000 mPa to 60 mPa in about 5 minutes after ejaculation; (2) The shape of the hysteresis loops of shear stress versus shear rate was changed from the counter-clockwise direction, that enclosed a large area, into the clockwise direction, that enclosed a very small area. CONCLUSION: Human ejaculate originally possesses semi-solid or visco-elastic body behavior and in 5 minutes after liquefaction, it becomes a thixotropic fluid or shearing thinning fluid with very low viscosity.

Influence of shearing Stress to the Expression of Endothelin by Vascular Endothelial Cells.

Using radioimmunoassay and Northern blot, the differences in endothelin and its mRNA expression were studied for cultured cerebral micro-vascular endothelial cells (from WKY and SHR rats) which exposed to flow shear stress at 0, 0.5, 1, 2 Pa for 24 h. The results showed that the endothelin and its mRNA expression of endothelial cells from both WKY and SHR rats proportionally increased according to the shear stress values at 0, 0.5 and 1 Pa, at 2 Pa, however the endothelin and its mRNA expression did not increase further. When comparing both rat systems, the SHR's levels of endothelin and its mRNA expression were higher than WKY's. The results indicated that the levels of endothelin and its mRNA expression were proportional to shear stress in 0-1 Pa in WKY and SHR rat systems and the levels of endothelin and its mRNA of SHR system were higher than those of WKY's. Our results indicate that the vascular wall in SHR system may be more contractile, less relaxative, with lower remodeling ability and thus more easily to mediate atherosclerosis.