Power analyses for correlations from clustered study designs

Power analysis constitutes an important component of modern clinical trials and research studies. Although a variety of methods and software packages are available, almost all of them are focused on regression models, with little attention paid to correlation analysis. However, the latter is arguably a simpler and more appropriate approach for modelling concurrent events, especially in psychosocial research. In this paper, we discuss power and sample size estimation for correlation analysis arising from clustered study designs. Our approach is based on the asymptotic distribution of correlated Pearson-type estimates. Although this asymptotic distribution is easy to use in data analysis, the presence of a large number of parameters creates a major problem for power analysis due to the lack of real data to estimate them. By introducing a surrogacy-type assumption, we show that all nuisance parameters can be eliminated, making it possible to perform power analysis based only on the parameters of interest. Simulation results suggest that power and sample size estimates obtained under the proposed approach are robust to this assumption.

Effect of Epilobium angustifolium L. extracts and polyphenols on cell proliferation and neutral endopeptidase activity in selected cell lines

The ability of Epilobium extracts and polyphenols to induce neutral endopeptidase (NEP) activity and to inhibit the proliferation in cell lines with high NEP expression (SK-N-SH) and with low NEP expression (PC-3) was investigated. Epilobium extracts enhanced in a dose-depend manner NEP activity in both cell lines with additional inhibition of cell proliferation. The sensitivity of cells depended on basal enzyme activity. SK-N-SK cells were much more sensitive than PC-3 cells. Oenothein B enhanced NEP activity at a concentration of 5-40 microM while quercetin-3-glucuronide and quercetin-3-O-(6"-gal-loyl) galactoside showed slight or no activity at a concentration of 100 microM. The comparison of activities of the extracts with oenothein B, a dimeric macrocyclic ellagitannin, suggests that the latter is mostly responsible for the observed effects. Taking into account the role of NEP in the homeostasis of signalling peptides, Epilobium angustifolium extracts may be a potential herbal remedy in diseases connected with the disturbed metabolism of signaling peptides caused by an unbalanced neutral endopeptidase activity.

Power analyses for longitudinal trials and other clustered designs

Existing methods for power and sample size estimation for longitudinal and other clustered study designs have limited applications. In this paper, we review and extend existing approaches to improve these limitations. In particular, we focus on power analysis for the two most popular approaches for clustered data analysis, the generalized estimating equations and the linear mixed-effects models. By basing the derivation of the power function on the asymptotic distribution of the model estimates, the proposed approach provides estimates of power that are consistent with the methods of inference for data analysis. The proposed methodology is illustrated with numerous examples that are motivated by real study designs.

Flupentixol and trifluperidol reduce interleukin-1 beta and interleukin-2 release by rat mixed glial and microglial cell cultures

Neuroleptics penetrate into the brain, where they act not only on neurons but probably also on glial cells. In the available literature, there are no reports on the effect of neuroleptics on cytokine release in glia cultures. The aim of this study was to evaluate the effect of neuroleptics on the release of proinflammatory cytokines (IL-1beta and IL-2) by mixed glial and microglial cell cultures. Trifluperidol at 20 and 2 muM reduced IL-beta secretion by mixed glial cultures after 3 days of exposure. Trifluperidol at 20, 2 and 0.2 muM diminished IL-beta secretion after 1 day of incubation. Trifluperidol at 20 and 2 muM reduced IL-2 release after 1 and 3 days of exposure. Flupentixol at 20 and 2 muM reduced IL-1beta by mixed glial cell cultures after 3 days of exposure. Flupentixol at 20, 2 and 0.2 muM caused diminution of IL-1beta release after 1 day of exposure. Flupentixol at 20 and 2 muM reduced IL-2 release after 1 day of incubation. Flupentixol at 20, 2 and 0.2 muM diminished IL-2 release after 3 days of exposure. Flupentixol at 20, 10, 2 and 0.2 muM reduced IL-1beta release by microgial cell cultures. Flupentixol at 20, 10 and 2 muM reduced release of IL-2 by microglial cells after 1 day of exposure. The results of the present study suggest that neuroleptics have an inhibiting effect on the release of glial cytokines, but clinical significance this results remains to be elucidated.

Effects of atorvastatin, simvastatin, and fenofibrate therapy on monocyte chemoattractant protein-1 secretion in patients with hyperlipidemia

OBJECTIVE

Monocytes that migrate into the arterial wall participate in the development and, eventually, rupture of the atherosclerotic plaque. The aim of this study was to evaluate the secretion of monocyte chemoattractant protein-1 (MCP-1) by monocytes from hyperlipidemic patients treated with hypolipidemic drugs, namely fenofibrate, simvastatin, or atorvastatin to determine what role is played by these drugs in the development and stabilization of the atherosclerotic plaque.

METHODS

Fifty-four hyperlipidemic patients, who did not respond to a low-fat diet, were treated with fenofibrate, simvastatin, or atorvastatin (18 patients in each group) for 1 month. The control group included 18 normolipidemic, healthy, age-matched participants. Ten hyperlipidemic patients were effectively treated with hypolipidemic diet alone for 1 month. This group was compared with a control group of ten healthy subjects. To accurately evaluate the adhesion molecule levels, we excluded hyperlipidemic patients and control subjects with any inflammatory disease. Before and after treatment, monocytes were isolated from peripheral blood. After stimulation with lipopolysaccharide (LPS), MCP-1 secretion was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

MCP-1 levels were significantly higher in hyperlipidemic patients than controls: 15.8+/-0.47, 16.7+/-0.23, and 14.9+/-0.45 compared with 12.36+/-0.42 ng/ml. Fenofibrate, atorvastatin, and simvastatin significantly decreased MCP-1 levels from 15.8+/-0.47 to 8.79+/-0.89, from 16.7+/-0.23 to 7.46+/-0.73, and from 14.9+/-0.45 to 10.3+/-0.8 ng/ml, respectively. In the diet-treated group of hyperlipidemic patients, the level of MCP-1 before therapy was significantly higher than in controls (16.89+/-0.31 vs 12.45+/-0.36 ng/ml). The diet therapy caused a significant decrease in levels of MCP-1 to 15.1+/-0.36 ng/ml. There was a correlation between the decreased levels of lipids and the decreased release of MCP-1 in the patients treated with hypolipemic drugs.

CONCLUSION

The drug-induced decrease in MCP-1 secretion in hyperlipidemic patients suggests that, apart from acting on lipids, the hypolipidemic drugs studied may directly inhibit the activity of monocytes.

Effects of fenofibrate and simvastatin on plasma sICAM-1 and MCP-1 concentrations in patients with hyperlipoproteinemia

OBJECTIVE

The most important mechanism through which high plasma lipid levels trigger the formation of atherosclerotic lesions involves a change in the expression of adhesion molecules on endothelial and smooth muscle cells. The aim of this study was to evaluate an extralipid effect of fenofibrate and simvastatin by examination of MCP-1 and ICAM-1 plasma concentration after 1-month hypolipemic therapy as well as MCP-1 and ICAM-1 plasma concentration after 1-month therapy with low-fat diet alone.

METHODS

Twenty patients with HLPIIb or HLPIIa, who did not respond to a low-fat diet, were treated with micronized fenofibrate or simvastatin, respectively, for 1 month. The control group included 18 normo-lipidemic, healthy age-matched participants; 10 patients with HLPIIa were effectively treated with a low-fat diet for 1 month. This group was compared to a control group of 10 healthy subjects. The plasma adhesion molecule levels were measured by an ELISA method before and after the treatment. To accurately evaluate the adhesion molecule levels, we excluded hyperlipidemic patients and control subjects with any inflammatory disease.

RESULTS

sICAM-1 levels were significantly higher in HLPIIa and HLPIIb patients (331 +/- 19 ng/ml and 423 +/- 23 ng/ml, respectively) compared with the control group (236 +/- 12 mg/ml). MCP-1 levels were also significantly higher in HLPIIa and HLPIIb patients (170 +/- 9 pg/ml and 183 +/- 15 pg/ml, respectively) compared with the control group (100 +/- 4 pg/ml). Fenofibrate (200 mg daily) significantly decreased sICAM-1 (by 17%) and MCP-1 levels (by 12.5%). Simvastatin (20 mg daily) caused a significant decrease (by 10.5%) in sICAM-1 levels only. Restriction in dietary lipids resulted in a significant decrease in the levels of cholesterol (8%), LDL cholesterol (14.9%) and ApoB (12.7%), which was accompanied by a significant decrease in the levels of sICAM-1 (8.7%) and MCP-1 (16.1%).

CONCLUSION

The results of this study suggest that high lipid levels are accompanied by increased levels of sICAM-1 and MCP-1 and that hypolipidemic therapy only slightly decreases the levels of these molecules compared with plasma lipids. The hypolipidemic diet-related decrease in the levels of lipids, ICAM-1 and MCP-1 suggests that it is a drug-induced decrease in lipid levels but not a direct action of the drugs on endothelial cells, smooth muscle cells or macrophages that leads to a decrease in the levels of adhesion molecules.

Generalized covariance-adjusted canonical correlation analysis with application to psychiatry

The lack of control over covariates in practice motivates the need for their adjustment when measuring the degree of association between two sets of variables, for which canonical correlation is traditionally used. In most studies however, there is also a lack of control over the attributes of responses for the sets of variables of interest. In particular, a portion of the response variable may be continuous and the other discrete. For such settings, the traditional partial canonical correlation approach is restrictive, since a covariate-adjustment for a set of continuous variables is assumed. By ignoring the assumption of continuous variates and proceeding with a partial canonical correlation analysis in the presence of continuous and discrete variates, results in canonical correlation estimates that are not consistent. In this paper we generalize the traditional partial canonical correlation approach to covariate-adjustment by allowing the response variables to contain continuous, as well as discrete, variates. The methodology is illustrated with a psychiatric application for examining which sleep variables relate to which depressive symptoms, as measured by commonly used constructs that presents with both continuous and discrete outcomes.

The risk of atherosclerosis in patients with impaired glucose tolerance

OBJECTIVES

Glucose metabolism disorders usually coexist with dyslipidemia and coagulation/fibrinolysis disturbances. Increase of insulin resistance followed by hyperinsulinemia leads to enhanced protein synthesis, including production of apolipoproteins. As a result, the structure of Low Density Lipoprotein (LDL) becomes small and dense. This augments lipid infiltration into the arterial wall. Following this process monocyte adhesion to endothelium initiates atherosclerotic injury. One of the markers of this inflammatory reaction is Monocyte Chemoattractant Peptide-1 (MCP-1). A lot of inflammatory mediators affect both oxidative modification of LDL and coagulation processes being responsible for anti-fibrinolytic predominance. Plasminogen Activator Inhibitor-1 (PAI-1) is a marker of this state. Therefore the aim of this study is to evaluate the marker of the oxidation processes (oxLDL) as well as prothrombotic (PAI-1) and inflammatory state (MCP-1) markers in patients with Impaired Glucose Tolerance (IGT).

METHODS

The study was carried out on 16 subjects: 10 with biochemically confirmed IGT and 6 age-matched healthy persons without such disorders. Following tests were performed: OGTT, HbA(1c) level as well as TCh, HDL, LDL and TG. Plasma concentrations of oxLDL, PAI-1 and MCP-1 were measured using ELISA method.

RESULTS

In patients with Impaired Glucose Tolerance plasma levels of oxLDL were significantly higher compared to control group (67.6 +/- 0.9 U/l vs. 57.8 +/- 4.0 U/l; p < 0.01) in spite of LDL levels, which did not reveal such difference. MCP-1 plasma concentration compared to control group occurred to be significantly increased in experimental group as well (156.4 +/- 9.2 ng/ml vs. 125.4 +/- 1.9 ng/ml; p < 0.05). PAI-1 level revealed most significant difference (84.0 +/- 1.8 ng/ml vs. 43.7 +/- 2.7 ng/ml; p < 0.0001).

CONCLUSIONS

It is concluded that patients with Impaired Glucose Tolerance should be considered as a group in which atherogenic modification of lipoproteins occurred. Also plasma inflammatory as well as prothrombotic markers concentration was elevated.

[Pulmonary lymphangioleiomyomatosis: presentation and results of treatment]

Lymphangioleiomyomatosis is a rare lung disease of unknown aetiology that affects only women. Eight premenopausal women with LAM confirmed by lung biopsy specimens were observed in 1984-2001. The most common presenting feature was exertional dyspnea (6) followed by chylous pleural effusions and pneumothoraces. In two women severe airflow obstruction was observed at presentation. HRCT revealed characteristic cysts in all cases. All women were given hormonal therapy (tamoxifen, medroxyprogesterone). The best results of treatment were achieved in cases with chylothoraces.

Characterization of a recombinant porcine follistatin in a heat shock expression system

The role of follistatin in ovarian function has yet to be fully elucidated; it is present in low concentration in vivo and it is difficult to obtain suitable quantities of follistatin for characterization. We have cloned porcine follistatin cDNA in an expression system that uses the heat shock protein promoter BoHSP70. Recombinant follistatin with apparent molecular masses of 39, 46, 48, 50 kDa was expressed and secreted into culture medium at concentrations of 400–500 μg × 20 mL-1 × 150 cm-2 flask (4 × 107 cells). In ligand blots, the recombinant follistatin was shown to be immunologically similar to native follistatin and to bind to recombinant activin A. Porcine granulosa cells dissected from 1–3 mm follicles from immature gilts were cultured with recombinant follistatin or with a follistatin monoclonal antibody to examine the activity of the recombinant follistatin. At a physiologically relevant concentration of 1 μg mL-1 the recombinant porcine follistatin suppressed the accumulation of estradiol-17β (P < 0.05). There was a trend for estradiol-17β accumulation in the presence of 10 μg mL-1 of monoclonal anti-follistatin antibody (P = 0.1). This expression system consistently produced large quantities of recombinant porcine follistatin, which is immunologically and biologically similar to follistatin, and is capable of independently inhibiting estratiol-17βproduction in vitro. Key words: Porcine, follistatin, heat shock promoter, glycoprotein, ovary, estradiol

Double-blind, randomized, placebo-controlled study of topical 5% acyclovir-1% hydrocortisone cream (ME-609) for treatment of UV radiation-induced herpes labialis

Immunopathology is recognized as an important component of infectious disease manifestations, and corticosteroids have been used as an adjunct to antimicrobial therapy for a variety of conditions. Antiviral therapy of herpes labialis has been shown to result in only a small reduction in the time to healing and the duration of pain. To determine if topical application of a combination product containing 5% acyclovir and 1% hydrocortisone (ME-609) could provide benefit to herpes labialis patients, 380 immunocompetent adults with a history of herpes labialis were exposed to experimental UV radiation (UVR) to induce a recurrence. On day 2, just before the appearance of the majority of lesions ("delayed" lesions), subjects were randomized to receive active medication or vehicle control six times per day for 5 days. Overall, 120 of 380 patients developed delayed classical lesions, of whom 50 of 190 (26%) had been treated with ME-609 and 70 of 190 (37%) had received placebo (a reduction of 29% [P = 0.02]). Healing time, measured as the time to normal skin, was reduced by treatment with ME-609 (9.0 days for treated patients versus 10.1 days for the controls [P = 0.04]). There was a trend toward a reduction in the maximum lesion size in the ME-609 recipients compared to that in the controls (43 versus 60 mm(2), respectively [P = 0.07]). The treatment had no effect on lesion pain, but ME-609 treatment reduced the number of patients with moderate or severe tenderness. Compared to treatment with a placebo, treatment with the combination antiviral-immunomodulatory cream provided benefit to patients with experimental UVR-induced herpes labialis, reducing classical lesion incidence, healing time, lesion size, and lesion tenderness. ME-609 is a novel product that merits further evaluation as a treatment for cold sores.

Plasma cytokines as predictors of coronary heart disease

BACKGROUND AND OBJECTIVE

Growing body of evidence explicitly suggests the significant role of inflammatory processes in vascular diseases related to atherosclerosis. Monocytes, present in every phase of atherogenesis, are the principal cells accumulating in atherosclerotic plaque. Monocyte Chemotactic Protein 1 (MCP-1) seems to influence firm adherence of rolling monocytes and infiltration into the artery wall. Although the significant meaning of inflammation in atherogenesis has been proved, potential role of antiinflammatory cytokines remains unknown. Interleukin 10 (IL-10) is a major cytokine of pleiotropic antiinflammatory function known to exert inhibitory effects on monocytes. Recent data emerging from clinical and pathological studies suggest important role of thrombosis and fibrinolytic disorders in atherosclerosis complications especially in coronary heart disease (CHD). Individuals with greater Plasminogen Activator Inhibitor 1 (PAI-1) level are believed to be more susceptible to cardiovascular disease.

METHODS

In our study we measured the plasma levels of MCP-1, IL-10 and PAI-1 in 10 patients with stable angina and 10 healthy subjects. We also estimated its mutual correlations. The plasma levels of MCP-1, IL-10 and PAI-1 were determined with R&D kits (ELISA).

RESULTS

Plasma levels of MCP-1 were significantly higher (261.5+/-40.7 pg/mL vs 73.3+/-3.05 pg/mL; p<0.0002) and also levels of PAI-1 were higher (79.36+/-5.8 ng/mL vs 35.88+/-1.38 ng/mL; p<0.0001) in patients with SA compared with the healthy control subjects. Whereas plasma levels of IL-10 were lower (11.6+/-0.5 pg/mL vs 16.5+/-0.4 pg/mL; p<0.0001) compared with control group and correlated with both MCP-1 plasma level (r=-0.67; p<0.0015) and PAI-1 concentration (r=-0.69; p<0.0008).

CONCLUSION

The data obtained confirm the predictive role of cytokines in patients with stable coronary heart disease. The negative correlation of anti-inflammatory IL-10 and PAI-1 was also found.