A Comparison of Bimatoprost 0.03% Versus the Fixed-Combination of Latanotoprost 0.005% and Timolol 0.5% in Adult Patients With Elevated Intraocular Pressure: An Eight-Week, Randomized, Open-Label Trial

Introduction and Purpose: Bimatoprost and the fixed combination of latanoprost with timolol maleate are 2 medications widely used to treat glaucoma and ocular hypertension (OHT). The aim of the study is to compare the efficacy of these 2 drugs in reducing intraocular pressure (IOP) after 8 weeks of treatment in patients with primary open angle glaucoma (POAG) or OHT. Methods: In this randomized, open-label trial, 44 patients with POAG or OHT were allocated to receive either bimatoprost (1 drop QD) or latanoprost/timolol (1 drop QD). Primary outcome was the mean diurnal IOP measurement at the 8th week, calculated as the mean IOP measurements taken at 8:00 AM, 10: 00 AM, and 12: 00 PM Secondary outcomes included the baseline change in IOP measured 3 times a day, after the water-drinking test (performed after the last IOP measurement), and the assessment of side effects of each therapy. Results: The mean IOP levels of latanoprost/timolol (13.83, SD = 2.54) was significantly lower than of bimatoprost (16.16, SD = 3.28; P < 0.0001) at week 8. Also, the change in mean IOP values was significantly higher in the latanoprost/timolol group at 10:00 AM (P = 0.013) and 12:00 PM (P = 0.01), but not at 8: 00 AM (P = ns). During the water-drinking test, there was no signifi cant difference in IOP increase (absolute and percentage) between groups; however, there was a signifi cant decrease in mean heart rate in the latanoprost/timolol group. Finally, no signifi cant changes in blood pressure and lung spirometry were observed in either groups. Conclusions: The fixed combination of latanoprost/timolol was significantly superior to bimatoprost alone in reducing IOP in patients with POAG or OHT. Further studies with large sample sizes should be taken to support the superior efficacy of latanoprost/timolol, as well as to better assess its profile of side effects.

Providing Integrity and Authenticity in DICOM Images: A Novel Approach

The increasing adoption of information systems in healthcare has led to a scenario where patient information security is more and more being regarded as a critical issue. Allowing patient information to be in jeopardy may lead to irreparable damage, physically, morally, and socially to the patient, potentially shaking the credibility of the healthcare institution. Medical images play a crucial role in such context, given their importance in diagnosis, treatment, and research. Therefore, it is vital to take measures in order to prevent tampering and determine their provenance. This demands adoption of security mechanisms to assure information integrity and authenticity. There are a number of works done in this field, based on two major approaches: use of metadata and use of watermarking. However, there still are limitations for both approaches that must be properly addressed. This paper presents a new method using cryptographic means to improve trustworthiness of medical images, providing a stronger link between the image and the information on its integrity and authenticity, without compromising image quality to the end user. Use of Digital Imaging and Communications in Medicine structures is also an advantage for ease of development and deployment.

Proposal for DICOM Multiframe Medical Image Integrity and Authenticity

This paper presents a novel algorithm to successfully achieve viable integrity and authenticity addition and verification of n-frame DICOM medical images using cryptographic mechanisms. The aim of this work is the enhancement of DICOM security measures, especially for multiframe images. Current approaches have limitations that should be properly addressed for improved security. The algorithm proposed in this work uses data encryption to provide integrity and authenticity, along with digital signature. Relevant header data and digital signature are used as inputs to cipher the image. Therefore, one can only retrieve the original data if and only if the images and the inputs are correct. The encryption process itself is a cascading scheme, where a frame is ciphered with data related to the previous frames, generating also additional data on image integrity and authenticity. Decryption is similar to encryption, featuring also the standard security verification of the image. The implementation was done in JAVA, and a performance evaluation was carried out comparing the speed of the algorithm with other existing approaches. The evaluation showed a good performance of the algorithm, which is an encouraging result to use it in a real environment.

Bioequivalence Evaluation of Single Doses of Two Tramadol Formulations: A Randomized, Open-Label, Two-Period Crossover Study in Healthy Brazilian Volunteers

Background: Tramadol is a well tolerated and effective analgesic used to treat moderate to severe pain. Several generic formulations of tramadol are available in Brazil; however, published information regarding their bioequivalence in the Brazilian population is not available. A study was designed for Brazilian regulatory authorities to allow marketing of a generic formulation. Objective: The purpose of this study was to compare the bioequivalence of 2 commercial tablet preparations containing tramadol 100 mg marketed for use in Brazil. Methods: A randomized, open-label, 2 x 2 crossover study was performed in healthy Brazilian volunteers under fasting conditions with a washout period of 12 days. Two tablet formulations of tramadol 100 mg (test and reference formulations) were administered as a single oral dose, and blood samples were collected over 24 hours. Tramadol plasma concentrations were quantified using a validated HPLC method. A plasma concentration time profile was generated for each volunteer and then mean values were determined, from which C(max), T(max), AUC(0-t), AUC(0-infinity), k(e), and t(1/2) were calculated using a noncompartmental model. Bioequivalence between the products was determined by calculating 90% CIs for the ratios of C(max), AUC(0-t), and AUC(0-infinity) values for the test and reference products using log-transformed data. Tolerability was assessed by monitoring vital signs (temperature, blood pressure, heart rate), laboratory tests (hematology, blood biochemistry, hepatic function, urinalysis), and interviews with the volunteers before medication administration and every 2 hours during the study. Results: Twenty-six healthy volunteers (13 men, 13 women) were enrolled in and completed the study. Mean (SD) age was 30 (6.8) years (range, 21-44 years), mean weight was 64 (8.3) kg (range, 53-79 kg), and mean height was 166 (6.4) cm (range, 155-178 cm). The 90% CIs for the ratios of C(max) (1.01-1.17), AUC(0-t) (1.00-1.13), and AUC(0-infinity) (1.00-1.14) values for the test and reference products fell within the interval of 0.80 to 1.25 proposed by most regulatory agencies, including the Brazilian regulatory body. No clinically important adverse effects were reported; only mild somnolence was reported by 4 volunteers and mild headaches by 5 volunteers, and there was no need to use medication to treat these symptoms. Conclusion: Pharmacokinetic analysis in these healthy Brazilian volunteers suggested that the test and reference formulations of tramadol 100-mg tablets met the regulatory requirements to assume bio-equivalence based on the Brazilian regulatory definition. (Clin Ther 2010;32:758-765) (C) 2010 Excerpta Medica Inc.

Monitoring the authenticity of Brazilian UHT milk: A chemometric approach

In this work, chemometric methods are reported as potential tools for monitoring the authenticity of Brazilian ultra-high temperature (UHT) milk processed in industrial plants located in different regions of the country. A total of 100 samples were submitted to the qualitative analysis of adulterants such as starch, chlorine, formal. hydrogen peroxide and urine. Except for starch, all the samples reported, at least, the presence of one adulterant. The use of chemometric methodologies such as the Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) enabled the verification of the occurrence of certain adulterations in specific regions. The proposed multivariate approaches may allow the sanitary agency authorities to optimise materials, human and financial resources, as they associate the occurrence of adulterations to the geographical location of the industrial plants. (c) 2010 Elsevier Ltd. All rights reserved.

Bioequivalence and pharmacokinetics of two zidovudine formulations in healthy Brazilian volunteers: An open-label, randomized, single-dose, two-way crossover study

Background: Zidovudine is a thymidine nucleoside reverse transcriptase inhibitor with activity against HIV type 1. Some (similar to 8) generic formulations of zidovudine are available in Brazil; however, based on a literature search, information concerning their bioavailability and pharmacokinetic properties in the Brazilian population has not been reported. Objective: The aim of this study was to compare the bioavailability and pharmacokinetic properties of 2 capsule formulations of zidovudine 100 mg in healthy Brazilian volunteers. Methods: This open-label, randomized, 2-way crossover study utilized a 1-week washout period between doses. Blood samples were collected for 8 hours after a single dose of zidovudine 100-mg test (Zidovudina, Fundaqdo para o Remedio Popular, Sao Paulo, Brazil) or reference formulation (Retrovir (R), GlaxoSmithKline, Philadelphia, Pennsylvania). Plasma zidovudine concentrations were determined using a validated high-performance liquid chromatography method with ultraviolet detection at 265 nm. C-max, T-max, AUC(0-t), AUC(0-infinity), t(1/2), and the elimination constant (k(e)) were determined using noncompartmental analysis. The formulations were considered bioequivalent if the 90% CIS for C-max, AUC(0-t), and AUC(0-infinity) fell within the interval of 80 % to 125 %, the regulatory definition set by the US Food and Drug Administration (FDA). Results: Twenty-four healthy volunteers (12 males, 12 females; mean age, 27 years; weight, 60 kg; height, 167 cm) were enrolled and completed the study. The 90% CIs of the treatment ratios for the logarithmic-transformed values of C-max, AUC(0-t), and AUC(0-infinity) were 80.0% to 113.6%, 93.9% to 109.7%, and 93.6% to 110.1 %, respectively. The values for the test and reference formulations were within the FDA bioequivalence definition intervals of 80% to 125%. Conclusions: In this small study in healthy subjects, no statistically significant differences in C-max, AUC(0-t), and AUC(0-)infinity were found between the test and reference formulations of zidovudine 100-mg capsules. The 90% CIs for the mean ratio values for the test and reference formulations of AUC(0-t), AUC(0-infinity), and C-max indicated that the reported data were entirely within the bioequivalence acceptance range proposed by the FDA of 80% to 125% (using log-transformed data).

Additive Intraocular Pressure Reduction Effect of Fixed Combination of Maleate Timolol 0.5%/Dorzolamide 2% (Cosopt) on Monotherapy With Latanoprost (Xalatan) in Patients With Elevated Intraocular Pressure A Prospective, 4-week, Open-label, Randomized, Controlled Clinical Trial

Purpose: To evaluate the additive effect of dorzolamide/timolol fixed combination in patients under monotherapy with latanoprost. Patients and Methods: In this prospective, 4-week, randomized, open-label controlled clinical trial, patients with open-angle glaucoma or ocular hypertension, which presented at least 15% intraocular pressure (IOP) reduction after a minimum period of 15 days of monotherapy with latanoprost and whose IOP level was considered above the established target-IOP level were randomized to receive fixed combination of timolol/dorzolamide twice daily in one of eyes. The fellow eye was kept under monotherapy and was included in the control group. A modified diurnal tension curve (mDTC) followed by the water drinking test were performed in the baseline and week 4 visits to evaluate IOP profile between groups. Results: Forty-nine per-protocol patients were analyzed. After latanoprost monotherapy run-in period, IOP levels were significantly reduced (P<0.001) in both control and study groups to 15.34 +/- 2.96 mm Hg and 15.24 +/- 2.84 mm Hg (30.8% and 32.2% IOP reduction, respectively; P=0.552). At week 4, mean baseline diurnal IOP levels were 15.60 +/- 3.09 and 14.44 +/- 3.03 (7.4% difference; P=0.01). Mean baseline IOP modified diurnal tension curve peak after latanoprost run-in period were 17.47 +/- 3.68 mm Hg and 17.02 +/- 3.35 mm Hg (control and study eyes, respectively; P=0.530). At week 4 visit, mean water-drinking test peaks were significantly reduced in the study eye group in comparison with the control group: 19.02 +/- 3.81 mm Hg and 20.39 +/- 4.19 mm Hg, respectively (6.7% reduction; P=0.039). Conclusions: In our sample, dorzolamide 2%/timolol 0.5% fixed combination as add-on therapy in patients with open-angle glaucoma or ocular hypertension under monotherapy with latanoprost with IOP already in mid-teens levels may further enhance pressure reduction.

An Eight-week, Multicentric, Randomized, Interventional, Open-label, Phase 4, Parallel Comparison of the Efficacy and Tolerability of the Fixed Combination of Timolol Maleate 0.5%/Brimonidine Tartrate 0.2% Versus Fixed Combination of Timolol Maleate 0.5%/Dorzolamide 2% in Patients With Elevated Intraocular Pressure

Purpose: To compare the efficacy and tolerability of the fixed combination of timolol maleate 0.5%/brimonidine tartrate 0.2% versus fixed combination of timolol maleate 0.5%/dorzolamide 2% in patients with elevated intraocular pressure (IOP) over 8 weeks. Patients and Methods: This 8-week, multicentric. interventional, randomized, open-label, parallel group study was conducted Lit 4 centers in Brazil and 1 center in Argentina. Patients with open-angle glaucoma or ocular hypertension were randomized to receive bilaterally fixed combination of brimonidine/timolol maleate 0.5% or fixed combination of dorzolamide 2%/timolol 0.5% twice daily at 8:00 AM and 8:00 PM. A modified diurnal tension curve (8:00 AM 10:30 AM, 02:00 PM, and 4:00 PM) followed by the water drinking test (WDT), which estimates IOP peak of diurnal tension curve, were performed in the baseline and week-8 visits. Adverse events data were recorded at each visit. Results: A total of 210 patients were randomized (brimonidine/timolol, n = 111; dorzolamide/timolol, n = 99). Mean baseline IOP was 23.43 +/- 3.22 mm Hg and 23.43 +/- 4.06 mm Hg in the patients treated with brimonidine/timolol and dorzolamide/timolol, respectively (P = 0.993). Mean diurnal IOP reduction after 8 weeks were 7.02 +/- 3.06 mm Hg and 6.91 +/- 3.67 mm Hg. respectively (P = 0.811). The adjusted difference between groups (analysis of covariance) Lit week 8 was not statistically significant (P = 0.847). Mean baseline WDT peak was 27.79 +/- 4.29 mm Hg in the brimonidine/timolol group and 27.68 +/- 5.46 mm Hg in the dorzolamide/timolol group. After 8 weeks of treatment, mean WDT peaks were 20.94 +/- 3.76 mm Hg (P < 0.001) and 20.98 +/- 4.19 (P < 0.001), respectively. The adjusted difference between groups (analysis of covariance) was not statistically significant (P = 0.469). No statistical difference in terms of adverse events was Found between groups. Conclusions: Both fixed combinations were capable of significantly reducing the mean diurnal IOP, mean diurnal peak, and mean WDT peak after 8 weeks of treatment. Also, both fixed combinations are well tolerated with few side effects.

Relative Bioavailability of Two Oral Formulations of Risperidone 2 mg: A Single-Dose, Randomized-Sequence, Open-Label, Two-Period Crossover Comparison in Healthy Brazilian Volunteers

Background: Risperidone (RSP) is a benzisoxazole antipsychotic agent used to treat schizophrenia and other psychiatric illnesses in adults and children (including those with autism). After oral administration, RSP is completely absorbed from the gastrointestinal tract and undergoes hydroxylation to yield 9-hydroxyrisperidone (9-OH-RSP), an active metabolite that has a pharmacologic profile and potency similar to RSP. Objectives: The aims of this study were to compare the relative bioavailability of a pharmaceutical-equivalent (test) formulation with a reference formulation of oral RSP 2 mg, both available commercially on the Brazilian pharmaceutical market, and to generate data regarding the oral bioavailability of the tested drug in healthy Brazilian volunteers. Methods: This single-dose, randomized-sequence, open-label, 2-period crossover study was conducted in healthy Brazilian volunteers from August to December 2008. Subjects were randomly assigned to receive the test formulation followed by the reference formulation or vice versa, with a 30-day washout period between doses. Study drugs were administered after a 12-hour overnight fast. For pharmacokinetic analysis, blood samples were drawn at 0 (baseline), 0.25, 0.5, 1, 1.5, 3, 5, 8, 12, 24, 48, 72, 96, and 120 hours after administration. Plasma concentrations of RSP and 9-OH-RSP were determined using LC-MS/MS. The test and reference formulations were to be considered bioequivalent if the 90% CIs for the geometric mean test/reference ratios were within a predetermined range of 80% to 125%, in accordance with the policies of the Brazilian Sanitary Surveillance Agency and the US Food and Drug Administration. Tolerability was determined using clinical assessments, monitoring of vital signs, analysis of laboratory test results, and subject interviews regarding adverse events. Results: A total of 22 subjects were enrolled (11 men, 11 women; mean [SD] age, 32 [12] years [range, 18-58 years]; weight, 70.4 [11.9] kg [range, 50-103 kg]; height, 1.67 [0.08] m [range, 1.56-1.80 m]; and body mass index, 25 [4] kg/m(2) [range, 18-29 kg/m(2)]). For RSP, mean (SD) C(max) values were 12.6 (2.7) and 16.0 (2.3) ng/mL for the test and reference formulations, respectively. For 9-OH-RSP, mean C(max) values were 17.8 (1.3) and 21.0 (1.7) ng/mL for the test and reference formulations. The 90% CIs for the mean test/reference ratios for RSP C(max), AUC(0-120), and AUC(0-infinity) were 74% to 82%, 75% to 85%, and 76% to 85%, respectively, and 83% to 87%, 75% to 79%, and 75% to 78% for 9-OH-RSP. The related adverse events (headache, low back pain, drowsiness, standing hypotension, local postvenipuncture ecchymoses, insomnia, nausea, and vomiting) were transient and mild. Conclusions: This single-dose study found that the test and reference formulations of oral RSP 2 mg did not meet the Brazilian and US regulatory criteria for bioequivalence in these fasting, healthy volunteers. The study formulations appeared to be well tolerated. (Clin Ther 2010;32:2106-2115) (C) 2010 Elsevier HS Journals, Inc.

Timing of Dose Relative to Sexual Intercourse Attempt in Previous Sildenafil Citrate Users Treated with Tadalafil: A Geographical Comparison from a Single Arm, Open-Label Study

Introduction. Previous research has demonstrated that sildenafil citrate users alter dosing-sexual attempt behavior when switched to tadalafil. The impact of geography and culture on sexual behavior with phosphodiesterase type 5 (PDE5) inhibitor treatment has not been fully investigated. Aim. To describe and compare the changes in dosing-sexual attempt behavior with sildenafil citrate vs. tadalafil treatment across four distinct geographies: Asia, Australia/New Zealand (ANZ), Central Eastern Europe/Middle East (CEE/ME), and Latin America (LA). Methods. Data from a single-arm, open-label clinical trial conducted in 21 countries from November 2002 to May 2004 were used in this analysis. Men with erectile dysfunction and a history of >= 6-week prior sildenafil citrate use continued sildenafil citrate treatment for 4 weeks then switched to tadalafil for 8 weeks. Dosing instructions were provided. Main Outcomes Measures. Timing of dose and sexual intercourse was assessed through patient diaries for the final 4 weeks of each treatment period. Results. A total of 2,760 men were enrolled: Asia 15.8%; ANZ 29.4%; CEE/ME 19.7%; LA 35.1%. The median time from dosing to intercourse was significantly increased during tadalafil treatment across all geographical regions; however, the magnitude of increase differed significantly by geography (P < 0.0001). The Asian cohort demonstrated the shortest duration between dosing and sexual intercourse attempts (irrespective of drug), and altered sexual behavior the least upon switching to tadalafil. The ANZ cohort demonstrated the longest duration between dosing and sexual intercourse attempts (irrespective of drug), and altered sexual behavior the most upon switching to tadalafil. Conclusion. Men with a history of established sildenafil citrate use alter their dose-attempt behavior when treated with tadalafil irrespective of geography. However, the extent to which sexual behavior alters is not uniform across geographical regions, suggesting that dosing instructions and duration of drug effectiveness, in combination with personal and cultural preferences, may determine sexual behavior with PDE5 inhibitor use. Rubio-Aurioles E, Glina S, Abdo CHN, Hernandez-Serrano R, Rampazzo C, Sotomayor M, West TM, Gallagher GL, and Lenero E. Timing of dose relative to sexual intercourse attempt in previous sildenafil citrate users treated with tadalafil: A geographical comparison from a single arm, open-label study. J Sex Med 2009;6:2836-2850.

Aripiprazole for Patients with Schizophrenia and Schizoaffective Disorder: An Open-Label, Randomized, Study Versus Haloperidol

Introduction: Aripiprazole, a dopamine D(2) receptor partial agonist, has also partial agonist activity at serotonin (5-HT)(1A) receptors and antagonist activity at 5-HT(2A) receptors. Methods: In this 8-week, multicenter, randomized, parallel-group, open-label, flexible-dose study, patients diagnosed with schizophrenia or schizoaffective disorder were randomized to aripiprazole 15-30 mg/day or haloperidol 10-15 mg/day. Results: Patients treated with both aripiprazole and haloperidol improved from baseline in Positive and Negative Syndrome Scale total, positive, and negative scores as well as in Clinical Global Impressions scores (all P<.001). At the end of the study, the percentage of patients classified as responders-according to >= 40% reduction in the Positive and Negative Syndrome Scale negative subscale score-was significantly higher in the aripiprazole group (20%) than in the haloperidol group (0%) (P<.05). Additionally, a higher number of patients receiving haloperidol required more anticholinergic medications (P<.001) than aripiprazole-treated patients, whereas more aripiprazole (45.5%) than haloperidol-treated patients (12.9%) required benzodiazepines (P=.002). At endpoint, rates of preference of medication were higher in the aripiprazole group (63.2%) than in the haloperidol group (21.7%), as expressed by patients and caregivers (P=.001). Conclusion: Aripiprazole and haloperidol had similar efficacy in terms of reduction of overall psychopathology. Although aripiprazole has been demonstrated to be superior concerning negative symptoms and in terms of tolerability (extrapyramidal symptoms) and preferred by patients and caregivers than haloperidol, significantly more aripiprazole-treated patients required benzodiazepines.

Ventilation Distribution Studies Comparing Technegas and ""Gallgas"" Using (68)GaCl(3) as the Label

Ventilation distribution can be assessed by SPECT with Technegas. This study was undertaken in piglets with different degrees of ventilation inhomogeneity to compare PET using (68)Ga-labeled pseudogas or ""Gallgas"" with Technegas. Methods: Twelve piglets were studied in 3 groups: control, lobar obstruction, and diffuse airway obstruction. Two more piglets were assessed for lung volume (functional residual capacity). Results: In controls, SPECT and PET images showed an even distribution of radioactivity. With lobar obstruction, the absence of ventilation of the obstructed lobe was visible with both techniques. In diffuse airway obstruction, SPECT images showed an even distribution of radioactivity, and PET images showed more varied radioactivity over the lung. Conclusion: PET provides detailed ventilation distribution images and a better appreciation of ventilation heterogeneity. Gallgas with PET is a promising new diagnostic tool for the assessment of ventilation distribution.

Quetiapine versus clomipramine in the augmentation of selective serotonin reuptake inhibitors for the treatment of obsessive-compulsive disorder: a randomized, open-label trial

After 12 weeks of selective serotonin reuptake inhibitor (SSRI) monotherapy with inadequate response, 10 patients received clomipramine and 11 received quetiapine as augmentation agents of the SSRI. The primary outcome measure was the difference between initial and final scores of the YaleBrown Obsessive-Compulsive Scale (Y-BOCS), rated in a blinded fashion, and the score of clinical global improvement (CGI-I). Statistical analyses were performed using nonparametric tests to evaluate treatment efficacy and the difference between treatment groups. Percentile plots were constructed with YBOCS scores from the clomipramine and quetiapine groups. Considering response a >= 35% reduction in the initial Y-BOCS score plus a rating of `much improved` or `very much improved` on CGI-I, four of eleven quetiapine patients and one out of ten clomipramine patients were classified as responders. The mean final Y-BOCS score was significantly lower than baseline in the quetiapine augmentation group (P = 0.023), but not in the clomipramine augmentation group (P = 0.503). The difference between groups showed a trend towards significance only at week 4, the mean Y-BOCS score being lower for those receiving quetiapine (P = 0.052). A difference between groups was also observed at week 4 according to percentile plots. These results corroborate previous findings of quetiapine augmentation efficacy in obsessive-compulsive disorder (OCD). Clomipramine augmentation did not produce a significant reduction in Y-BOCS scores. Higher target maximum dosages might have yielded different results.

DNA alters the bilayer structure of cationic lipid diC14-amidine: A spin label study

Cationic lipids-DNA complexes (lipoplexes) have been used for delivery of nucleic acids into cells in vitro and in vivo. Despite the fact that, over the last decade, significant progress in the understanding of the cellular pathways and mechanisms involved in lipoplexes-mediated gene transfection have been achieved, a convincing relationship between the structure of lipoplexes and their in vivo and in vitro transfection activity is still missing. How does DNA affect the lipid packing and what are the consequences for transfection efficiency is the point we want to address here. We investigated the bilayer organization in cationic liposomes by electron spin resonance (ESR). Phospholipids spin labeled at the 5th and 16th carbon atoms were incorporated into the DNA/diC14-amidine complex. Our data demonstrate that electrostatic interactions involved in the formation of DNA-cationic lipid complex modify the packing of the cationic lipid membrane. DNA rigidifies the amidine fluid bilayer and fluidizes the amidine rigid bilayer just below the gel-fluid transition temperature. These effects were not observed with single nucleotides and are clearly related to the repetitive charged motif present in the DNA chain and not to a charge-charge interaction. These modifications of the initial lipid packing of the cationic lipid may reorient its cellular pathway towards different routes. A better knowledge of the cationic lipid packing before and after interaction with DNA may therefore contribute to the design of lipoplexes capable to reach specific cellular targets. (c) 2009 Elsevier B.V. All rights reserved.

Multiple stages of detergent-erythrocyte membrane interaction-A spin label study

The various stages of the interaction between the detergent Triton X-100 (TTX-100) and membranes of whole red blood cells (RBC) were investigated in a broad range of detergent concentrations. The interaction was monitored by RBC hemolysis-assessed by release of intracellular hemoglobin (Hb) and inorganic phosphate- and by analysis of EPR spectra of a fatty acid spin probe intercalated in whole RBC suspensions, as well as pellets and supernatants obtained upon centrifugation of detergent-treated cells. Hemolysis finished at ca. 0.9 mM TTX-100. Spectral analysis and calculation of order parameters (S) indicated that a complex sequence of events takes place, and allowed the characterization of various structures formed in the different stages of detergent-membrane interaction. Upon reaching the end of cell lysis, essentially no pellet was detected, the remaining EPR signal being found almost entirely in the supernatants. Calculated order parameters revealed that whole RBC suspensions, pellets, and supernatants possessed a similar degree of molecular packing, which decreased to a small extent up to 2.5 mM detergent. Between 3.2 and 10 mM TTX-100, a steep decrease in S was observed for both whole RBC suspensions and supernatants. Above 10 mM detergent, S decreased in a less pronounced manner and the EPR spectra approached that of pure TTX-100 micelles. The data were interpreted in terms of the following events: at the lower detergent concentrations, an increase in membrane permeability occurs: the end of hemolysis coincides with the lack of pellet upon centrifugation. Up to 2.5 mM TTX-100 the supernatants consist of a (very likely) heterogeneous population of membrane fragments with molecular packing similar to that of whole cells. As the detergent concentration increases, mixed micelles are formed containing lipid and/or protein, approaching the packing found in pure TTX-100 micelles. This analysis is in agreement with the models proposed by Lasch (Biochim. Biophys Acta 1241 (1995) 269-292) and by Le Maire and coworkers (Biochim. Biophys. Acta 1508 (2000) 86-111). (C) 2010 Elsevier B.V. All rights reserved.