Finite-element analysis of arterial anastomoses with vein, Dacron and PTFE grafts

A finite-element simulation of an end-to-end artery/graft anastomosis has been presented in this study to evaluate the distribution of compliance and stresses in the vicinity of the anastomosis due to any mismatch in compliance characteristics. The arterial wall was assumed to be made of linear isotropic elastic material in this simplified model and a static analysis was performed with a mean arterial pressure loading of the artery-graft model. Anastomoses to vein grafts and both Dacron and polytetrafluoroethylene (PTFE) grafts were studied. The results suggested the presence of a hypercompliant zone on the arterial side and a region of high tensile stresses in the wall on the graft side of the anastomosis. The presence of a hypercompliant zone has been reported from previous in vivo studies. The hypercompliance was larger with Dacron and PTFE grafts compared with that with the vein graft. However, larger tensile stresses were present in the wall of the vein graft compared with the synthetic grafts. The analysis further showed that increasing the diameter of the graft compared with the host artery to increase flow through the implant will result in a significant increase in the hypercompliance on the arterial side. Such simulation studies may prove valuable in studying the effects of compliance mismatch and suggest ways to improve the design of small diameter vascular grafts.

Evidence for heat-stable liver cytosol substance(s) capable of causing oxidative activation of fructose 1,6-bisphosphatase

The endogenous fructose 1,6-bisphosphatase (FBPase) in chicken liver extract undergoes a drastic increase in activity if the pH of the extract is in the alkaline range. Greater and more consistent activation occurs when purified FBPase, placed inside dialysis sack, is incubated in liver extract. Maximal activation (over 16-fold) is accompanied by the disappearance of 4 highly reactive sulfhydryl groups (SH) per molecule of enzyme. The activating effect of the extract remains essentially unchanged after heating to 100 degrees C. Activation can be reversed by dithiothreitol. These data show the existence in liver cytosol of heat-stable substance(s) capable of activating FBPase presumably by forming disulfide bonds with the enzyme's highly reactive SH groups.

[Quality standard of kaixiong shunqi pills]

This paper adds TLC identification of binglang and other three cruds drugs to the quality control of kakxiong shunqi pills incorporated in Chinese Pharmacopoeia. The contents of magnolol and honokinol were determined by TLC scanning. The method is simple, rapid accurate, and useful in controlling the quality of kaixiong shunqi pills.

[Determination of glycyrrhetinic acid in radix Glycyrrhizae by TLC densitometry]

A TLC densitometric method for the determination of glycyrrhetinic acid in Radix Glycyrrhizae is described. The method is accurate, sensitive and simple. The recovery of glycyrrhetinic acid is 98.30% and the coefficient of variation of five samplings is 2.20%.

Stress distribution on the cusps of a polyurethane trileaflet heart valve prosthesis in the closed position

In this paper, a finite element analysis of the stress distribution on the cusps of a polyurethane trileaflet heart valve prosthesis in the closed position is presented. The geometry of the valve was modified from a relationship proposed by Ghista and Reul (J. Biomechanics 10, 313-324, 1977). The effects of variations in stent height, leaflet thickness and coaptation area on the stress distribution were also analyzed. Analyses were performed with both rigid and flexible stents for the trileaflet valve in order to delineate the effect of stent flexibility on the leaflet stress distribution. The results showed that regions of stress concentration were present near the commissural attachment similar to those predicted with the bioprostheses. The stresses on the leaflets were reduced by increasing the stent height with both rigid and flexible stents. Selectively increasing the leaflet thickness near the commissures and also increasing the coaptation area did not prove to reduce the leaflet stresses when the stent flexibility was taken into account. The possible effect of high stresses on the structural integrity of polyurethane leaflets and its relationship with calcification is yet to be investigated.

[Determination of tangshenoside I in Codonopsis pilosula Nannf. by TLC-UV spectrophotometric method]

A method of thin layer chromatographic separation and ultraviolet spectrophotometric determination of tangshenoside I in Codonopsis pilosula is described. A comparison of the contents in various samples is made. The contents of tangshenoside I in frosted sample have been found to be twice as much as in normal drug. The recovery of tangshenoside I is 99.92% and the coefficient of variation of eight samplings is 1.77%.

[Chemical constituents of Codonopsis pilosula Nannf]

An exclusive constituent has been isolated from the water soluble parts of root of Codonopsis pilosula for the first time. The constituent has been confirmed to be tangshenosid I.

Activation of chicken liver fructose- 1,6-bisphosphatase by oxidized glutathione

Treatment of chicken liver fructose- 1,6-bisphosphatase with oxidized glutathione (GSSG) leads to an increase in activity. This activation is markedly enhanced if treatment is performed in the presence of AMP or Mn2+. The effects of AMP and Mn2+ appear to be synergistic. The maximal activation is over 13-fold and is accompanied by the disappearance of 4 sulfhydryl groups per molecule of enzyme. Both fructose 1,6-bisphosphate and fructose 2,6-bisphosphate can largely prevent this activation. Activation can be reversed by dithiothreitol or cysteine. It appears that GSSG activates this enzyme by thiol/disulfide exchanges with the enzyme's specific sulfhydryl groups.

Changes in lung hyaluronidase activity associated with lung growth, injury and repair

We measured lung hyaluronidase activity in rats during postnatal life and during the repair of oxygen-induced lung injury. Hyaluronidase activity increased rapidly after birth and peaked at 16-fold the initial value at 8 days. The peak preceded decreased cell proliferation and the onset of differentiation; this is consistent with current concepts of the role of hyaluronidase. During the repair of lung injury, hyaluronidase activity increased to 2.5-fold the control value at 1 day post-injury, but had decreased by 3 days. This early peak is probably related to simultaneous cell proliferation and differentiation. We postulate that changes in hyaluronidase can influence lung growth and repair and that the system may be amenable to manipulation.