Resistin levels and inflammatory and endothelial dysfunction markers in obese postmenopausal women with type 2 diabetes mellitus.

BACKGROUND: Obesity-associated coronary heart disease (CHD) risk is higher in women than in men with type 2 diabetes (T2DM). Resistin, an adipokine secreted by adispose tissue, may contribute to this higher risk. AIMS: To explore the relationships among resistin levels and common inflammatory and endothelial dysfunction markers and CHD risk in obese post-menopausal T2DM women. METHODS: Serum levels of resistin, hsCRP, IL-6, Soluble vascular cell adhesion molecule (sVCAM), homocysteine (tHcy), HOMA-IR and metabolic parameters were determined in a group of 132 T2DM women with and without documented CHD and in 55 non-diabetic women. RESULTS: Resistin, sVCAM, IL-6 and tHcy levels were comparable in T2DM and controls. CHD women showed higher resistin, sVCAM and tHcy levels than those without CHD, and for resistin this difference remained significant after age-adjustment (P = 0.013); conversely hsCRP were ~ 2X higher in T2DM women than in controls (P = 0.0132) without any difference according to CHD history. At univariate analysis resistin levels were significantly associated with age, waist circumference, hypertension, tHcy, hsPCR, sVCAM, IL-6, HDL-cholesterol, triglycerides and creatinine levels, but only creatinine, triglycerides, hsCRP, IL-6 and sVCAM were independently associated to resistin levels at stepwise regression analysis. Resistin levels were independently associated to CHD, increasing the risk by 1.15 times (0.986-1.344 95% CI), together with age, tHcy, LDL-C and hypertension. CONCLUSIONS: Circulating resistin levels were comparable in obese/overweight T2DM and control women. In T2DM women, resistin levels correlated with markers of renal function, systemic inflammation and endothelial dysfunction and were independently associated with a higher CHD risk.

Lipid and non-lipid cardiovascular risk factors in postmenopausal type 2 diabetic women with and without coronary heart disease.

BACKGROUND: Coronary heart disease (CHD) is the leading cause of death in diabetic women. In addition to hyperglycemia, other factors may contribute to the excessive cardiovascular risk. AIM: In this study we evaluated common and emerging risk factors in a selected group of postmenopausal type 2 diabetic women with (n = 36) and without CHD (n = 59), not taking lipid-lowering medications. METHODS: Clinical and lifestyle data were collected, and metabolic and lipid profile, as well as fasting plasma levels of total homocysteine (tHcy), folate, vitamin B12, C-reactive protein (hsCRP), interleukin 6 (IL-6), and vascular cell adhesion molecule-1 (VCAM-1) were measured in all participants. RESULTS: Age, menopause and diabetes duration, family history for cardiovascular disease, prevalence of hypertension and current insulin use were greater in diabetic women with than without CHD (P < 0.05 for all comparisons). CHD women also showed higher levels of triglycerides, small dense LDL (sdLDL), remnant-like particle cholesterol, tHcy, and VCAM-1, and a lower creatinine clearance (P < 0.05 all). Conversely, the two groups were comparable for BMI, waist circumference, smoking habit, fasting plasma glucose, HbA1c, total cholesterol, low-density lipoprotein cholesterol (LDL-C), HDL cholesterol, folate, vitamin B12, hsCRP and IL-6 levels. At multivariate analysis, lower creatinine clearance (OR = 0.932, P = 0.017) and higher sdLDL serum concentration (OR = 1.224, P = 0.037) were the strongest risk factors associated with CHD in this population, whereas no significant association was noted with LDL-C. CONCLUSIONS: Our data suggest that beyond LDL-C, a lower creatinine clearance and more subtle alterations of LDL particles, together with a constellation of several well known and emerging cardiovascular risk factors, are stronger contributors to the high CHD risk of diabetic women.

Menopause modulates homocysteine levels in diabetic and non-diabetic women.

High total homocysteine (tHcy) plasma levels may contribute to the increased cardiovascular risk of Type 2 diabetic women. However, to date, data on factors modulating tHcy concentration in this population are scarce. Fasting tHcy, vitamin B12, folate plasma levels, and the methylene tetrahydrofolate reductase (MTHFR) C677T genotype as well as clinical, biochemical, and lifestyle variables were compared in 91 Type 2 diabetic and 91 matched non-diabetic women (40 pre- and 51 post-menopausal, in each group). Fasting tHcy concentration did not differ between diabetic and control women, even after multivariable adjustment. In both groups, tHcy levels increased after menopause, but the differences were weakened after multivariable adjustment. The MTHFR genotype distribution was in accordance with the Hardy-Weinberg equilibrium, with a similar TT frequency in diabetic (22.2 %) and control women (19.8%). Overall, tHcy plasma concentration was higher in TT homozygous compared to other genotypes. We found a menopause-genotype interaction on tHcy levels (p=0.068 for menopause*genotype interaction); overall, the increase of tHcy concentration in TT subjects was limited to pre-menopause (p<0.0001; adjusted p=0.024), and this was confirmed after considering diabetic and control women separately (p=0.001 and p=0.01, respectively). At multivariate analysis, menopause was an independent correlate of tHcy concentration, together with creatinine, folate and MTHFR genotype. Our data show that menopause has a strong influence on tHcy concentration even in Type 2 diabetic women and demonstrate, for the first time, that it may modulate the association between tHcy and the common MTHFR polymorphism both in diabetic and non-diabetic women.

A rapid microbiotest for the detection of cyanobacterial toxins.

Cyanobacteria occur widely in lakes, reservoirs, ponds, and slow flowing rivers. Many species are known to produce toxins (cyanotoxins), a number of which are of concern for health. Cyanotoxins vary in chemical structure and may be found intracellular or released into water. There is not only a wide variation in the toxicity of known cyanotoxins but a substantial number of toxins have to date not been identified chemically. Chemical analysis of cyanotoxins is nowadays not used for routine monitoring because it is time consuming, it requires specialized equipment and expertise, and is hence expensive. There is hence an urgent need for rapid tests in surface waters to detect cyanobacterial toxins because of the need for safe drinking water and safe natural bathing waters, which may be burdened by cyanobacterial blooms or scums. Previous investigations have already shown that larvae of the anostracan crustacean Thamnocephalus platyurus are quite sensitive to neurotoxic and hepatotoxic cyanotoxins. The present paper reports on the sensitivity comparison of the (1 h) Rapidtoxkit (based on a sublethal endpoint) and the (24 h) Thamnotoxkit microbiotest (based on mortality). Both assays make use of larvae of T. platyurus. The Rapidtoxkit is a new microbiotest that determines the decrease of ingestion of colored particles by the crustacean larvae, which are stressed by a short exposure to toxicants. Fifteen cyanobacterial samples composed of laboratory strains and natural bloom samples were tested by both microbiotests. All samples were also analyzed concurrently by HPLC for microcystins and cylindrospermopsin. The correlation coefficient between the two microbiotests (r = 0.82) showed the very good correspondence between the sublethal and the lethal effects. No known toxins could be detected in some samples, although the latter were found highly toxic to the test organisms in both bioassays. These results point to the presence of unknown toxin(s) produced by some cyanobacteria such as e.g., the Cylindrospermopsis raciborskii strain isolated from Lake Balaton in Hungary. This comparative study clearly showed that the 1 h Rapidtoxkit is an attractive rapid alternative to the Thamnotoxkit microbiotest.

Improved allocation of costs through analysis of variation in data: planning of laboratory studies.

BACKGROUND: When developing a new laboratory test for study of human diseases, it is important to identify and control internal and external sources of variation that affect test results. It is also imperative that the precision of the test not only meets pre-established requirements and not exceed allowable total error, but also that these objectives are reached without undue expenditure of either time or financial resources. METHODS: This study applies statistical principles in designing a cost-effective experimental approach for determining the analytical precision of a new test. This approach applies the statistical concept of variance components to the problem of balancing a pre-established level of analytical precision against expenses incurred in achieving this precision. RESULTS: We demonstrated (1) estimation of variance components, (2) use of these estimates for improving allocation of costs within the experiment, and (3) use of these estimates for determining the optimal number of replicate measurements. CONCLUSIONS: Although elimination of all sources of variation that can affect laboratory test results is unlikely, the application of analysis of variance (ANOVA) statistical techniques can lead to a cost-effective allocation of resources for estimating the precision of a laboratory test.

Subpopulations of high density lipoproteins in homozygous and heterozygous Tangier disease.

Tangier disease (TD) is characterized by severe high-density lipoproteins (HDL) deficiency, hypercatabolism of HDL constituents, impaired cellular cholesterol efflux, and mutations in the gene of ATP-binding cassette 1 (ABC-1). In the present study, we determined plasma lipid and apolipoprotein levels, and HDL subpopulations, in 110 subjects from a large TD kindred in which the proband was homozygous for an A-->C missense mutation at nucleotide 5338 of the ABC-1 transcript. In the proband HDL-C, apoA-I, and apoA-II concentrations were 2, 1, and 2 mg/dl, respectively, apoA-I was present only in prebeta(1), while apoA-II was found free of apoA-I in two distinct alpha mobility subpopulations with different sizes. The smaller size particles contained only apoA-II while the larger one contained apoA-II and apo(a). Relative to unaffected male relatives (n=30), male heterozygotes (n=21) had significant reductions (P<0.001) in plasma HDL-C (-45%), apoA-I (-34%), apoA-II (-59%), apoA-IV (-40%), Lp(a) (-62%), and apoB (-55%) concentrations, and a significant increase (P<0.05, +33%) in plasma apoC-III levels. Female heterozygotes (n=11) similarly had significant reductions (P<0.001) in the concentrations of plasma HDL-C (-42%), apoA-I (-27%), apoA-II (-52%), Lp(a) (-27%), and (P<0.01) apoA-IV (-28%), apoB (-13%), and a significant increase (P<0.05) in plasma apoE levels (+29%) as compared to unaffected female relatives (n=41). Large size HDL subpopulations, especially the two LpA-I particles: alpha(1) and prealpha(1) were dramatically reduced in both male and female heterozygotes relative to their unaffected family members. Since apoA-II decreased more than apoA-I in both male and female heterozygotes, the ratios of apoA-I/apoA-II were significantly (P<0.01) increased. The prevalence of CHD was 60% higher in the 32 heterozygotes than in the 71 unaffected relatives even though the latter group was on average 7 years older. We conclude that TD homozygotes have only prebeta(1) apoA-I-containing HDL subpopulations, while heterozygotes have HDL that is selectively depleted in the large alpha(1), prealpha(1), and alpha(2), prealpha(2) subpopulations, resulting in HDL particles that are small in size, poor in cholesterol, but relatively enriched in apoA-I compared to those of their unaffected relatives. These abnormalities appear to result in a higher risk of CHD in heterozygotes than in unaffected controls.

Distribution of ApoA-I-containing HDL subpopulations in patients with coronary heart disease.

High density lipoproteins (HDLs) and their subspecies play a role in the development of coronary heart disease (CHD). HDL subpopulations were measured by 2-dimensional nondenaturing gel electrophoresis in 79 male control subjects and 76 male CHD patients to test the hypothesis that greater differences in apolipoprotein (apo)A-I-containing HDL subpopulations would exist between these 2 groups than for traditional lipid levels. In CHD subjects, HDL cholesterol (HDL-C) was lower (-14%, P<0.001), whereas total cholesterol and the low density lipoprotein cholesterol/HDL-C ratio were higher (9% [P:<0.05] and 21% [P:<0.01], respectively) compared with control levels. No significant differences were found for low density lipoprotein cholesterol, triglyceride, and apoA-I levels. In CHD subjects, there were significantly (P:<0.001) lower concentrations of the large lipoprotein (Lp)A-I alpha(1) (-35%), pre-alpha(1) (-50%), pre-alpha(2) (-33%), and pre-alpha(3) (-31%) subpopulations, whereas the concentrations of the small LpA-I/A-II alpha(3) particles were significantly (P:<0.001) higher (20%). Because alpha(1) was decreased more than HDL-C and plasma apoA-I concentrations in CHD subjects, the ratios of HDL-C to alpha(1) and of apoA-I to alpha(1) were significantly (P:<0.001) higher by 36% and 57%, respectively, compared with control values. Subjects with low HDL-C levels (35 mg/dL). Therefore, we stratified participants according to HDL-C concentrations into low and normal groups. The differences in lipid levels between controls and HDL-C-matched cases substantially decreased; however, the significant differences in HDL subspecies remained. Our research findings support the concept that compared with control subjects, CHD patients not only have HDL deficiency but also have a major rearrangement in the HDL subpopulations with significantly lower alpha(1) and pre-alpha(1-3) (LpA-I) and significantly higher alpha(3) (LpA-I/A-II) particles.

Cellular cholesterol efflux in heterozygotes for tangier disease is markedly reduced and correlates with high density lipoprotein cholesterol concentration and particle size.

Tangier disease (TD), caused by mutations in the ATP-binding cassette 1 (ABC-1) gene, is a rare genetic disorder characterized by severe deficiency of high density lipoproteins (HDL) in the plasma, hypercatabolism of HDL, and defective apolipoprotein (apo)-mediated cellular cholesterol efflux. In the present study, we assessed plasma lipid concentrations, HDL particle size and subspecies, and cellular cholesterol efflux in 9 TD heterozygotes from a kindred in which the proband was homozygous for an A-->C missense mutation at nucleotide 5338 of the ABC-1 transcript. Relative to age- and gender-matched controls from the Framingham Offspring Study (FOS), TD heterozygotes had significant reductions (P < 0.000) in HDL-C (-54% female; -40% male) and apoA-I (-33% female; -37% male) concentrations, as well as significantly less cholesterol (-68% female; -58% male) distributed in the largest HDL subclasses, H5 and H4. Consequently, HDL particle size (nm) was significantly smaller (P < 0.000) in TD heterozygotes (8.6 +/- 0.6 female; 8.7 +/- 0.1 male) relative to FOS controls (9.4 +/- 0.4 female; 9.0 +/- 0.3 male). Further studies demonstrated that apoA-I-mediated cellular cholesterol efflux in TD heterozygotes was essentially half that of controls (11 +/- 2 vs. 20 +/- 3% of total [(3)H]cholesterol, P < 0. 001), with strong correlations observed between cholesterol efflux and both HDL-C level (r = 0.600) and particle size (r = 0.680). In summary, our data demonstrate that apolipoprotein-mediated cholesterol efflux is aberrant in TD heterozygotes, as it is in homozygotes. This finding, along with the associations observed between HDL-C concentration, HDL particle size, and cholesterol efflux, supports the concept that plasma HDL-C levels are regulated, in part, by cholesterol efflux, which in turn influences HDL particle size and, ultimately, HDL apoA-I catabolism.

Differential response to low-fat diet between low and normal HDL-cholesterol subjects.

Heart attacks frequently occur in normolipidemic subjects with low concentration of high density lipoproteins (35 mg/dL). We hypothesized that as subjects with low HDL-C already have low HDL concentrations, the major decrease of HDL-C will occur in subjects with normal HDL-C when a low-fat diet is consumed. Normolipidemic male subjects consumed three diets differing in total fat and saturated fat composition (AAD: 37%, Step-1: 28%, Step-2: 24% total fat) for 6 weeks in a three-period double-blind randomized crossover design. Plasma lipids and apolipoproteins were determined and changes in distribution of HDL subpopulations were evaluated. As a result of a low-fat diet, low HDL-C individuals slightly decreased their HDL-C, but substantially decreased their LDL-C resulting in a significant improvement in the LDL-C/HDL-C ratio. However, subjects with normal HDL-C levels decreased both their LDL-C and HDL-C resulting in an unchanged LDL-C/HDL-C ratio. We also observed significant differences in response to low-fat diets in HDL-C and alpha(1) concentrations between low and normal HDL-C subjects. In the normal HDL-C group, consumption of a low-fat diet also resulted in redistribution of apoA-I-containing HDL subpopulations, indicated by a decrease in the large apoA-I-only alpha(1) subpopulation. These data demonstrate that male subjects with low HDL-C respond to a low-fat diet differently than individuals with normal HDL-C.

Flow visualization analysis for evaluation of shear and recirculation in a new closed-type, monopivot centrifugal blood pump.

Flow visualization has great potential in analyzing flow patterns of centrifugal blood pumps to locate possible hemolysis and thrombus formation sites. This study focused on the said phenomena thought to correlate with areas of high shear velocity and stagnation and analyzed a new closed-type centrifugal blood pump. As a result of analyzing the flow of inlet and front gap of the impeller, flow in the front gap was approximately 30% of the external flow. Visualization in the back gap showed sufficient exchange also. Analysis in the volute area and around the washout holes revealed high shear locations and quantified the highest shear velocity. Maximum shear on the volute wall was found to be 9,000-19,000 s-1 and was located in the 0.2-mm vicinity of the wall. Based on these results, previous hemolysis tests, and small pump size, one concludes that the analyzed closed-type centrifugal pump has a relatively smooth flow suitable for a totally implantable artificial heart.

Flow visualization study to improve hemocompatibility of a centrifugal blood pump.

A correlation study was conducted among quantitative flow visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing gap widths on the flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small radial gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth flow and low shear. The small radial gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small radial gap itself is important. It was also confirmed by detailed flow visualization and simple laminar shear analysis near the wall that the small radial gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small radial gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.

Development of design methods for a centrifugal blood pump with a fluid dynamic approach: results in hemolysis tests.

The purpose of this study was to examine the relationship between local flow conditions and the hemolysis level by integrating hemolysis tests, flow visualization, and computational fluid dynamics to establish practical design criteria for centrifugal blood pumps with lower levels of hemolysis. The Nikkiso centrifugal blood pump was used as a standard model, and pumps with different values of 3 geometrical parameters were tested. The studied parameters were the radial gap between the outer edge of the impeller vane and the casing wall, the position of the outlet port, and the discharge angle of the impeller vane. The effect of a narrow radial gap on hemolysis was consistent with no evidence that the outlet port position or the vane discharge angle affected blood trauma in so far as the Nikkiso centrifugal blood pump was concerned. The radial gap should be considered as a design parameter of a centrifugal blood pump to reduce blood trauma.

Computational fluid dynamics analysis to establish the design process of a centrifugal blood pump: second report.

To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the radial gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.

Characterization of phospholipids in pre-alpha HDL: selective phospholipid efflux with apolipoprotein A-I.

Previously, we have shown that lipid-free apoA-I, when incubated with fibroblasts, will produce lipoproteins of pre-alpha mobility (Asztalos, B. F., et al. 1997. Arterioscler. Thromb. Vasc. Biol. 17: 1630-1636). In order to understand the nature of these pre-alpha particles, we further characterized their lipid content. The pre-alpha particles are high density lipoproteins, having a median density of 1.08 g/ml. They have a surface charge of -18.45 mV. The phospholipid composition of these particles showed that they have 4% each of phosphatidyl ethanolamine and inositol; 69% phosphatidyl choline and 18% sphingomyelin. This phospholipid composition is different from those of plasma HDL (81% phosphatidyl choline, 13% sphingomyelin), plasma membrane on the fibroblasts, and whole fibroblast phospholipid. To demonstrate that the pre-alpha mobility resides in the lipids, lipids from pre-alpha lipoproteins were reconstituted with lipid-free apoA-I. The resultant particles retained their pre-alpha mobility. We conclude that apoA-I may react with specific regions of plasma membrane to acquire this unusual lipid composition and that pre-alpha mobility is caused in part by the unusual phospholipid composition.

Flow visualization as a complementary tool to hemolysis testing in the development of centrifugal blood pumps.

With a 250% scaled-up pump model, high speed video camera, and argon ion laser light sheet, flow patterns related to hemolysis were visualized and analyzed with 4 frame particle tracking software. Different flow patterns and shear distributions were clarified by flow visualization for pumps modified to have different hemolysis levels. A combination of in vitro hemolysis tests, flow visualization, and CFD analysis suggested a close relationship between hemolysis and high shear caused by small impeller/casing gaps. Because arbitrary cross sections can be illuminated by laser light sheet, flow visualization is a useful tool in finding locations related to hemolysis in the design process of rotary blood pumps.

Washout hole flow measurement for the development of a centrifugal blood pump.

Washout holes in the impeller of a centrifugal blood pump reduce thrombus formation in areas where blood is apt to stagnate, especially in the back gap of the impeller. In this study, flow through the washout holes is quantified by pressure measurement and flow visualization with a 300% scaled-up model to understand the force driving flow through the washout holes and the flow itself. When external circuit resistance is constant, pressure distribution normalized by the square of the tip speed is constant and independent of the impeller rotational speed. The ratio of the flow rate through the washout holes to the flow rate of the external circuit is also constant. When the external circuit resistance increases, the pressure difference at the washout holes between the front and back gap of the impeller increases and generates a greater flow rate through the washout holes.

Development of design methods of a centrifugal blood pump with in vitro tests, flow visualization, and computational fluid dynamics: results in hemolysis tests.

There are few established engineering guidelines aimed at reducing hemolysis for the design of centrifugal blood pumps. In this study, a fluid dynamic approach was applied to investigate hemolysis in centrifugal pumps. Three different strategies were integrated to examine the relationship between hemolysis and flow patterns. Hemolytic performances were evaluated in in vitro tests and compared with the flow patterns analyzed by flow visualization and computational fluid dynamic (CFD). Then our group tried to establish engineering guidelines to reduce hemolysis in the development of centrifugal blood pumps. The commercially available Nikkiso centrifugal blood pump (HPM-15) was used as a standard, and the dimensions of 2 types of gaps between the impeller and the casing, the axial and the radial gap, were varied. Four impellers with different vane outlet angles were also prepared and tested. Representative results of the hemolysis tests were as follows: The axial gaps of 0.5, 1.0, and 1.5 mm resulted in normalized index of hemolysis (NIH) values of 0.0028, 0.0013 and 0.0008 g/100 L, respectively. The radial gaps of 0.5 and 1.5 mm resulted in NIH values of 0.0012 and 0.0008 g/100 L, respectively. The backward type vane and the standard one resulted in NIH values of 0.0013 and 0.0002 g/100 L, respectively. These results revealed that small gaps led to more hemolysis and that the backward type vane caused more hemolysis. Therefore, the design parameters of centrifugal blood pumps could affect their hemolytic performances. In flow visualization tests, vortices around the impeller outer tip and tongue region were observed, and their patterns varied with the dimensions of the gaps. CFD analysis also predicted high shear stress consistent with the results of the hemolysis tests. Further investigation of the regional flow patterns is needed to discuss the cause of the hemolysis in centrifugal blood pumps.

Role of free apolipoprotein A-I in cholesterol efflux. Formation of pre-alpha-migrating high-density lipoprotein particles.

This article characterizes products formed by the interaction of purified apolipoprotein (apo) A-I and human fibroblasts. Fibroblasts were incubated with different concentrations of purified apoA-I (1 to 30 micrograms/mL) in tissue culture medium for different periods of time (0 to 24 hours). The medium was then characterized by one- (agarose) and two-dimensional (agarose: polyacrylamide nondenaturing gradient gel) electrophoresis. At any given concentration of apoA-I, the rate of cellular cholesterol efflux appeared linear over 24 hours. Incubating purified apoA-I with fibroblasts for 4 hours, we detected five pre-alpha lipoproteins with particle sizes between 114 and 684 kDa. Formation of pre-alpha lipoproteins was concentration-dependent. At low concentrations (below 5 micrograms/mL apoA-I), all purified apoA-I (with pre-beta mobility) was converted to pre-alpha lipoproteins. At higher concentrations (greater than 5 micrograms/mL apoA-I), more apoA-I remained with pre-beta mobility. The pre-alpha lipoproteins were characterized by colocalization of apoA-I particles with 14C-cholesterol and 32P-phospholipids. Results showed that the pre-alpha particle of lowest molecular weight contained phospholipid and apoA-I but no cholesterol. The remaining pre-alpha particles contained all three substances. When pre-alpha particles were subjected to ultracentrifugation, all particles floated at d < 1.21 g/mL with some of the smallest phospholipid apoA-I only particles being present in the d > 1.21 g/mL fraction. Based on these results, we postulated that in the first stages of reverse cholesterol transport, pre-alpha lipoproteins are formed by the interaction of lipid free apoA-I and peripheral cells.

Normolipidemic subjects with low HDL cholesterol levels have altered HDL subpopulations.

Epidemiological studies have established that plasma concentration of HDL is inversely correlated with the risk of coronary heart disease, even in the absence of increased LDL cholesterol levels. We postulate that specific HDL subpopulations may be responsible for antiatherogenic properties of HDL. HDL subpopulations were quantitated by two-dimensional gel electrophoresis in 79 normolipidemic healthy male subjects. To eliminate the influence of diet, volunteers consumed an average American diet for 6 weeks. After the diet period, subjects were stratified according to their HDL cholesterol (HDL-C) levels to low HDL-C < 0.91 mmol/L (< 35 mg/dL), medium > 0.91 < 1.30 mmol/L (> 35 < 50 mg/dL), and high > or = 1.30 mmol/L (> or = 50 mg/dL) groups. Plasma triglycerides and insulin levels were in the normal range, but subjects with low HDL-C levels had higher concentrations of plasma triglycerides and insulin than subjects with medium or high HDL-C concentrations. The absolute concentration (mg/dL) of apoA-I in the largest alpha-migrating HDL subpopulation (alpha 1) was (P < .01) lower in the low HDL-C subjects compared with the medium and high HDL-C groups. The relative concentration (percent distribution) of apoA-I was decreased (P < .01) in alpha 1 and increased (P < .01) in alpha 3 subpopulations. A positive correlation between HDL-C and alpha 1 (P < .001) and a negative correlation between HDL-C and alpha 3 were observed. The inverse correlation of apoA-I distribution (relative concentration) between alpha 1 and alpha 3 suggests an interconversion of alpha 1 and alpha 3 subpopulations, possibly by cholesteryl ester transfer protein. Pre-beta subpopulations showed an inverse trend with HDL-C, while the pre-alpha subpopulation behaved similarly to the alpha-migrating subpopulation. Colocalization of apoA-I and apoA-II particles in the different HDL subpopulations demonstrated that alpha 1, pre-beta 1, and pre-beta 2 subpopulations are apoA-I-only particles rather than apoA-I:A-II particles.

Fluid dynamic characteristics of monopivot magnetic suspension blood pumps.

A monopivot magnetic suspension blood pump is a centrifugal pump under development with a magnetic suspension and a ceramic pivot to support the impeller with minimum contact. The pump size has been reduced by implementing a direct impeller drive mechanism in place of a magnetic coupling and motor. Flow visualization studies revealed that high shear, which seems to be closely related to hemolysis, concentrates in boundary layers near the walls. This implies that fluid dynamic shear can be reduced not by widening the gap, but by reducing the impeller velocity. Therefore, compared with the results of the previous semi-open curved vane impeller model, impeller velocity was reduced by 30% with a closed impeller having radial straight vanes, and smaller impeller/housing gaps. The volute shape around the impeller tip was also changed such that the outflow from the impeller enters along the center plane of the volute. To examine the effect of the improvements, hemolysis testing was conducted and found that the newly developed closed impeller model generated a lower level of hemolysis than the previous semi-open impeller model.