Hans Pottel

Correlation between the order parameter and the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene and an evaluation of membrane fluidity

Abstract In this paper it is shown that for 1,6-diphenyl-1,3,5-hexatriene there exists a simple analytical relation between the orientational order parameter and the steady-state fluorescence anisotropy. This relation is derived on semi-empirical grounds. The order parameter and the true microviscosity for membranes as calculated from steady-state measurements are evaluated. For biological membranes the estimation of the order parameter from steady-state experiments is feasible, but the evaluation of the true microviscosity is not reliable. Also, the physiological relevance of the order parameter is discussed.

I.V. and perineural dexamethasone are equivalent in increasing the analgesic duration of a single-shot interscalene block with ropivacaine for shoulder surgery: a prospective, randomized, placebo-controlled study

BACKGROUND Interscalene brachial plexus block (ISB) provides excellent, but time-limited analgesia. Dexamethasone added to local anaesthetics prolongs the duration of a single-shot ISB. However, systemic glucocorticoids also improve postoperative analgesia. The hypothesis was tested that perineural and i.v. dexamethasone would have an equivalent effect on prolonging analgesic duration of an ISB. METHODS We performed a prospective, double blind, randomized, placebo-controlled study. Patients presenting for arthroscopic shoulder surgery with an ISB were randomized into three groups: ropivacaine 0.5% (R); ropivacaine 0.5% and dexamethasone 10 mg (RD); and ropivacaine 0.5% with i.v. dexamethasone 10 mg (RDiv). The primary outcome was the duration of analgesia, defined as the time between performance of the block and the first analgesic request. Standard hypothesis tests (t-test, Mann-Whitney U-test) were used to compare treatment groups. The primary outcome was analysed by Kaplan-Meier survival analysis with a log-rank test and Coxs proportional hazards regression. RESULTS One hundred and fifty patients were included after obtaining ethical committee approval and patient informed consent. The median time of a sensory block was equivalent for perineural and i.v. dexamethasone: 1405 min (IQR 1015-1710) and 1275 min (IQR 1095-2035) for RD and RDiv, respectively. There was a significant difference between the ropivacaine group: 757 min (IQR 635-910) and the dexamethasone groups (P<0.0001). CONCLUSIONS I.V. dexamethasone is equivalent to perineural dexamethasone in prolonging the analgesic duration of a single-shot ISB with ropivacaine. As dexamethasone is not licensed for perineural use, clinicians should consider i.v. administration of dexamethasone to achieve an increased duration of ISB.

FDG-PET/CT for the preoperative lymph node staging of invasive bladder cancer.

BACKGROUND Locoregional lymph node metastasis is an important prognostic factor in patients with bladder cancer. Multimodal treatment, depending on preoperative stage, may improve survival. The standard imaging modalities for staging (computed tomography [CT] or magnetic resonance imaging [MRI]) have an accuracy range of 70-90% for lymph node staging. A more accurate preoperative diagnostic test could improve survival rates even more. OBJECTIVE To determine whether the use of 2-deoxy-2 [F] fluoro-D-glucose (FDG) positron emission tomography (PET) in combination with CT (FDG-PET/CT) can increase the reliability of preoperative lymph node staging in patients with nonmetastatic invasive bladder cancer (T2 or higher, M0) or recurrent high-risk superficial disease (T1G3 with or without Tis, M0). DESIGN, SETTING, AND PARTICIPANTS Fifty-one patients underwent a preoperative FDG-PET/CT between April 2004 and December 2007. Independent of the result for lymph node status, all patients underwent a radical cystectomy and an extended lymphadenectomy. The FDG-PET/CT and CT results were compared with the definitive pathologic results. MEASUREMENTS Among the 51 patients, 13 patients had metastatically involved locoregional lymph nodes, diagnosed on histopathology. In six patients, these nodes demonstrated increased FDG uptake on PET. In seven patients, PET/CT did not diagnose the positive lymph nodes. PET/CT was false positive in one patient. RESULTS AND LIMITATIONS For the diagnosis of node-positive disease, the accuracy, the sensitivity, and the specificity of FDG-PET/CT were 84%, 46%, and 97%, respectively. When analysing the results of CT alone, there was accuracy of 80%, sensitivity of 46%, and specificity of 92%. The use of FDG-PET/CT is hampered by technical limitations. CONCLUSIONS We found no advantage for combined FDG-PET/CT over CT alone for lymph node staging of invasive bladder cancer or recurrent high-risk superficial disease.

Analytical performance and clinical utility of the INNOTEST (R) PHOSPHO-TAU((181P)) assay for discrimination between Alzheimer's disease and dementia with Lewy bodies

Abstract Background: Total tau (T-tau) and β-amyloid(1-42) (Aβ1-42) levels in cerebrospinal fluid (CSF) can differentiate Alzheimers disease (AD) from normal aging or depressive pseudo-dementia. Differential diagnosis from dementia with Lewy bodies (DLB) in clinical settings is difficult. Methods: The analytical performance of the INNOTEST® PHOSPHO-TAU(181P) assay was validated in terms of selectivity, sensitivity, specificity, precision, robustness, and stability. Clinical utility of the assay alone, or combined with T-tau and Aβ1-42, for discrimination of AD (n=94) from patients suffering from DLB (n=60) or from age-matched control subjects (CS) (n=60) was assessed in a multicenter study. Results: CSF concentrations of tau phosphorylated at threonine 181 (P-tau181P) in AD was significantly higher than in DLB and CS. Discriminant analysis, a classification tree, and logistic regression showed that P-tau181P was the most statistically significant single variable of the three biomarkers for discrimination between AD and DLB. Conclusions: P-tau181P quantification is a robust and reliable assay that may be useful in discriminating AD from DLB. Clin Chem Lab Med 2006;44:1472–80.

Effect of orientational order on the decay of the fluorescence anisotropy in membrane suspensions. A new approximate solution of the rotational diffusion equation.

We discussed the time-dependence of fluorescent emission anisotropy of a cylindrical probe in membrane vesicles. We showed that, if the motion of the probe were described as diffusion in an anisotropic environment, it would be possible to determine not only the second-rank but also the fourth-rank orientational order parameter from the decay of the fluorescence anisotropy. The approximations involved were based on an interpolation of short-time and long-time behavior of the relevant correlation functions. A general expression was derived for the time dependence of the fluorescence anisotropy in closed form, which applies to any particular distribution model. It was shown to be in good agreement with previously reported results for the cone model and the Gaussian model. Finally, the applicability of the theory to time-resolved and differential phase fluorescence depolarization experiments was discussed.

Effect of orientational order on the decay of the fluorescence anisotropy in membrane suspensions. Experimental verification on unilamellar vesicles and lipid/alpha-lactalbumin complexes

Various models for the analysis of time-dependent fluorescence anisotropy measurements were evaluated. The discussion was based on the analysis of pulsed experiments with 1,6-diphenyl-1,3,5-hexatriene embedded in small unilamellar vesicles of dimyristoylphosphatidylcholine or dipalmitoylphosphatidylcholine and in dimyristoylphosphatidylcholine/alpha-lactalbumin complexes. It was shown that a recently proposed model (Van der Meer, W., H. Pottel, W. Herreman, M. Ameloot, H. Hendrickx, H. Schröder, 1984, Biophys. J., 46:515-523) described the data better than did the earlier suggested cone model (Kinosita K., Jr., S. Kawato, and A. Ikegami, 1977, Biophys. J., 20:289-305). This permitted the use of the new model for the estimation of the second- and fourth-rank order parameters on nonoriented systems. The results indicated that a fraction of the probes was oriented perpendicularly to the preferred direction of the lipids. An increase of the rotational correlation times of the fluorescent probe and a higher order of its environment were detected after the interaction of alpha-lactalbumin with the dimyristoylphosphatidylcholine vesicles at acidic pH at 24.2 degrees C.

An estimated glomerular filtration rate equation for the full age spectrum

BACKGROUND Glomerular filtration rate (GFR) is accepted as the best indicator of kidney function and is commonly estimated from serum creatinine (SCr)-based equations. Separate equations have been developed for children (Schwartz equation), younger and middle-age adults [Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation] and older adults [Berlin Initiative Study 1 (BIS1) equation], and these equations lack continuity with ageing. We developed and validated an equation for estimating the glomerular filtration rate that can be used across the full age spectrum (FAS). METHODS The new FAS equation is based on normalized serum creatinine (SCr/Q), where Q is the median SCr from healthy populations to account for age and sex. Coefficients for the equation are mathematically obtained by requiring continuity during the paediatric-adult and adult-elderly transition. Research studies containing a total of 6870 healthy and kidney-diseased white individuals, including 735 children, <18 years of age, 4371 adults, between 18 and 70 years of age, and 1764 older adults, ≥70 years of age with measured GFR (inulin, iohexol and iothalamate clearance) and isotope dilution mass spectrometry-equivalent SCr, were used for the validation. Bias, precision and accuracy (P30) were evaluated. RESULTS The FAS equation was less biased [-1.7 (95% CI -3.4, -0.2) versus 6.0 (4.5, 7.5)] and more accurate [87.5% (85.1, 89.9) versus 83.8% (81.1, 86.5)] than the Schwartz equation for children and adolescents; less biased [5.0 (4.5, 5.5) versus 6.3 (5.9, 6.8)] and as accurate [81.6% (80.4, 82.7) versus 81.9% (80.7, 83.0)] as the CKD-EPI equation for young and middle-age adults; and less biased [-1.1 (-1.6, -0.6) versus 5.6 (5.1, 6.2)] and more accurate [86.1% (84.4, 87.7) versus 81.8% (79.7, 84.0)] than CKD-EPI for older adults. CONCLUSIONS The FAS equation has improved validity and continuity across the full age-spectrum and overcomes the problem of implausible eGFR changes in patients which would otherwise occur when switching between more age-specific equations.

Establishing age/sex related serum creatinine reference intervals from hospital laboratory data based on different statistical methods.

BACKGROUND This is a retrospective study on a large hospital database to establish age- and sex-related mean values and reference ranges for serum creatinine (Scr), obtained with an IDMS-traceable, enzymatic method, in a Caucasian population. METHODS The database was filtered for unique entries to reduce the presence of correlated and pathological data. Three different statistical methods, a non-parametric method, the Bhattacharya procedure and a non-linear fit of the cumulative Gaussian distribution were used to estimate the serum creatinine-age dependency for men and women, from birth till 100 years of age. RESULTS Scr increases with age, equal for boys and girls, up to 14 years and with a much steeper slope for boys than for girls between 14 and 20 years. We show that the Scr-age pattern is constant between 20 and 70 years with a mean of 0.90 mg/dL [0.63-1.16 mg/dL] for men and 0.70 mg/dL [0.48-0.93 mg/dL] for women. Above 70, Scr starts to slowly increase again. CONCLUSIONS Indirect methods confirm the available reference intervals from healthy-volunteer studies and add information on age-periods not covered by these studies. As such, indirect methods can be used complementary to healthy-volunteer studies.

Inhibition of FK506 Binding Proteins Reduces α-Synuclein Aggregation and Parkinson's Disease-Like Pathology

α-Synuclein (α-SYN) is a key player in the pathogenesis of Parkinsons disease (PD). In pathological conditions, the protein is present in a fibrillar, aggregated form inside cytoplasmic inclusions called Lewy bodies. Members of the FK506 binding protein (FKBP) family are peptidyl-prolyl isomerases that were shown recently to accelerate the aggregation of α-SYN in vitro. We now established a neuronal cell culture model for synucleinopathy based on oxidative stress-induced α-SYN aggregation and apoptosis. Using high-content analysis, we examined the role of FKBPs in aggregation and apoptotic cell death. FK506, a specific inhibitor of this family of proteins, inhibited α-SYN aggregation and neuronal cell death in this synucleinopathy model dose dependently. Knockdown of FKBP12 or FKBP52 reduced the number of α-SYN aggregates and protected against cell death, whereas overexpression of FKBP12 or FKBP52 accelerated both aggregation of α-SYN and cell death. Thus, FK506 likely targets FKBP members in the cell culture model. Furthermore, oral administration of FK506 after viral vector-mediated overexpression of α-SYN in adult mouse brain significantly reduced α-SYN aggregate formation and neuronal cell death. Our data explain previously described neuroregenerative and neuroprotective effects of immunophilin ligands and validate FKBPs as a novel drug target for the causative treatment of PD.

Dual time-point FDG PET-CT for differentiating benign from malignant solitary pulmonary nodules in a TB endemic area

OBJECTIVE Fluorodeoxyglucose (FDG)-positron emission tomography (PET) is an accurate non-invasive imaging test for differentiating benign from malignant solitary pulmonary nodules (SPNs). We aimed to assess its diagnostic accuracy for differentiating benign from malignant SPNs in a tuberculosis (TB)-endemic area. METHODS Thirty patients, 22 men and 8 women, mean age 60 years, underwent dual time point FDG-PET/computed tomography (CT) imaging, followed by histological examination of the SPN. Maximum standard uptake values (SUVmax) with the greatest uptake in the lesion were calculated for two time points (SUV1 and SUV2), and the percentage change over time per lesion was calculated (%DSUV). Routine histological findings served as the gold standard. RESULTS Histological examination showed that 14 lesions were malignant and 16 benign, 12 of which were TB. SUVmax for benign and malignant lesions were 11.02 (standard deviation (SD) 6.6) v. 10.86 (SD 8.9); however, when tuberculomas were excluded from the analysis, a significant difference in mean SUV1max values between benign and malignant lesions was observed (p=0.0059). Using an SUVmax cut-off value of 2.5, a sensitivity of 85.7% and a specificity of 25% was obtained. Omitting the TB patients from analysis resulted in a sensitivity of 85.7% and a specificity of 100%. Mean %DSUV of benign lesions did not differ significantly from mean %DSUV of malignant lesions (17.1% (SD 16.3%) v. 19.4% (SD 23.7%)). Using a cut-off of %DSUV>10% as indicative of malignancy, a sensitivity of 85.7% and a specificity of 50% was obtained. Omitting the TB patients from the analysis yielded a sensitivity of 85.7% and a specificity of 75%. CONCLUSION Our findings suggest that FDG-PET cannot distinguish malignancy from tuberculoma and therefore cannot reliably be used to reduce futile biopsy/thoracotomy.