Combined oestrogen-progestogen replacement therapy does not inhibit low-density lipoprotein oxidation in postmenopausal women.

AIMS: The use of oestrogen containing hormone replacement therapy (HRT) is related to a significantly reduced atherosclerotic cardiovascular risk in postmenopausal women. Oestrogen is thought to be antioxidant and may inhibit low-density lipoprotein (LDL) oxidation in vitro. We investigated the effect of combined oestrogen and progestogen HRT on LDL oxidation in postmenopausal women. METHODS: Eighteen healthy women were given oestrogen/progestogen, and the susceptibility of LDL to oxidation was measured as the level of autoantibody to oxidative modified LDL and the production of conjugated dienes during copper-dependent oxidation after 3 and 6 months HRT. The levels of vitamin E, the major antioxidant in LDL, were also measured. RESULTS: After HRT, the anti-oxidatively modified LDL antibody level remained unchanged [1.58+/-0.16, 0.10 (-0.10, 0.26), and 0.08 (-0.09, 0.19), mean+/-s.d. at baseline, and mean change with 95% confidence intervals for differences at 3 and 6 months, respectively, P>0.05] as did the production of conjugated dienes when determined as lag phase [51.2+/-7.5, -0.3 (-3.9, 3.3), and 1.5 (-3.4, 6.4) min, P>0.05]. The LDL vitamin E content, measured as alpha-tocopherol, was also not altered [2.34+/-0.54, -0.07 (-0.27, 0.13), and -0.07 (-0.33, 0.16) nmol mg(-1) LDL, P>0.05] by treatment. CONCLUSIONS: Combined oestrogen and progestogen therapy for 6 months in postmenopausal women does not protect LDL against oxidation.

A 2-year study of lipid and lipoprotein changes in postmenopausal women with tibolone and estrogen-progestin.

OBJECTIVE: To assess changes in lipid-lipoprotein profile in postmenopausal women taking tibolone and estrogen-progestin, compared with untreated controls. METHODS: Sixty-three women were randomized to take a combined estrogen-progestin preparation (n = 31) or tibolone (n = 32), and 50 other women acted as controls. Fasting lipid-lipoprotein levels were measured over 96 weeks. RESULTS: The controls, who were older and postmenopausal longer than the therapy subjects, exhibited significant decreases in total (P < .05) and low-density lipoprotein (LDL) (P < .001) cholesterol and increases in triglyceride (P < .05) and lipoprotein (a) (P < .001) over the 96-week period of study. Lipoprotein (a) also decreased significantly in both treated groups (P < .001). Total and LDL cholesterol decreased and triglyceride increased in the estrogen-progestin group, but, compared with controls, these changes were not significant. Total cholesterol decreased in the tibolone group, although decreases in low- and particularly high-density lipoprotein (HDL) (P < .001) cholesterol and parallel decreases in apolipoprotein A1 (P < .001) and B (p < .01) were also observed. There was evidence of a reversion phenomenon in apolipoproteins A1 and B in all groups, and in lipoprotein (a) with tibolone. CONCLUSION: Some changes accompanying tibolone may be favorable and may counter its adverse effect on HDL cholesterol. Lowering of lipoprotein (a) was the only significant change found with estrogen-progestin.

Knowledge based lipid management system for general practitioners.

The aim of this system is to provide computer generated interpretative reports with management advice for General Practitioners (GPs). The lipid domain was chosen because of its importance in preventive medicine. Request forms to elicit extra clinical information were designed and distributed to a group of randomly selected GPs. Interpretation of laboratory and clinical data categorizes patients according to risk of coronary heart disease. The management system is rule based and provides advice on lifestyle modifications, diet and drug intervention. Previous clinical and laboratory results are taken into account in determining a management strategy. To date 435 request forms have been processed: 309 (71%) from first visits and 126 (29%) from follow-up visits. Normal lipid profiles were found in 19% of cases. There was 93% agreement between management advice given by the system and the expert. The system has now been modified and further evaluation is under way.

Verification testing of the bearings used in the electrohydraulic total artificial heart.

This article reports the verification testing performed on the ball bearings used in the electrohydraulic total artificial heart (EHTAH) device. The bearings were tested for 70 days under conditions intended to simulate those actually experienced by the bearings in the EHTAH device. Vibration analysis to predict the condition of the bearings, as well as diagnosis of the wear experienced by the bearings, was included in this study. Examination of the bearings using light microscopy indicated the presence of wear, and in some instances the contact surfaces had undergone temper coloring, a warning sign that hardness of the bearing may have been impaired, and that the bearing has experienced a temperature excursion. Temper coloring can be caused by too thick a coating of grease or by insufficient hydrodynamic film thickness. In this investigation, the vibration amplitudes at specific frequencies that correlated with the bearing components were monitored for change. From analysis of the vibration spectra, it was found that the change in amplitude did not predict the damage incurred by the bearings. The type of damage experienced by the bearings is difficult to predict using spectral analysis.

Effects of surface integrity on the fatigue life of thin flexing membranes.

It has been known for some time that surface integrity has an effect on the fatigue life of metals and "brittle" polymers. In cardiovascular applications of polymeric materials, emphasis is placed on elastomers having extended flexure lifetimes (i.e., fatigue life). The effect of surface integrity on the performance properties of Biomer (Ethicon, Inc, Somerville, NJ) a segmented polyurethane used in many blood contacting devices, is being investigated using uniaxial tensile tests in air at room temperature, and biaxial fatigue tests in deionized water at body temperature. Tensile tests were done using ASTM-D-882: Standard Test Methods for Tensile Properties of Thin Plastic Sheeting. No significant differences were noted in the stress-strain curves for specimens with various surface finishes. Fatigue tests were performed using an apparatus developed to allow for the exposure of thin-sheet polymer specimens to fluid at body temperature, while being biaxially strained. Because no standard test method was available, a test protocol was developed with reference to ASTM-D-671-78: Standard Test Methods for the Flexural Fatigue of Plastics by Constant Amplitude of Force. Stress versus life cycle data for specimens with differing surface finishes are being collected. Results to date suggest fatigue life of thin flexing membranes will decrease with increasing order of surface roughness, and fatigue properties are more sensitive to effects of changes in surface integrity than tensile properties measured by monotonic loading.