The association of adequate empirical treatment and time to recovery from bacteraemic urinary tract infections: a retrospective cohort study.

Our objective was to evaluate whether patients with bacteraemic urinary tract infection (UTI) who receive inadequate empirical therapy have worse outcomes than those with adequate therapy. This was a retrospective cohort study of patients with bacteraemic UTI. The exposure variable was adequate versus inadequate empirical antibiotic therapy (AEAT versus IEAT) within 24 h of culture collection. Primary endpoint was time to cure. The primary analysis used propensity score models with inverse probability of treatment weights. A secondary Cox proportional hazards modelling approach was used to test the robustness of this finding, and to evaluate other patient and pathogen predictors of time to cure. Of 469 patients with bacteraemic UTI, 368 (78.5%) received AEAT. There was no significant difference in mortality between those receiving AEAT and those receiving IEAT (adjusted OR 0.86, 95%CI 0.47-1.58). Receipt of AEAT had no association with time to cure (HR 0.93, 95%CI 0.73-1.19, p 0.55) or time to normalization of individual clinical variables. Cox proportional hazards modelling revealed that longer time to cure was associated with liver disease (HR 0.25, 95%CI 0.08-0.76, p 0.015), prior stroke (HR 0.73, 95%CI 0.54-0.99, p 0.044), empirical receipt of piperacillin-tazobactam (HR 0.77, 95%CI 0.59-0.99, p 0.044), qSOFA score >1 (HR 0.68, 95%CI 0.55-0.84, p < 0.001), and hospital-onset UTI (HR 0.53, 95%CI 0.39-0.71, p < 0.001). In conclusion, we found no association between AEAT and time to cure for patients with bacteraemic UTI. It may be appropriate to accept a higher risk threshold when choosing empirical antibiotic regimens, even in centres with high rates of resistant uropathogens.

Studying the result of underlay myringoplasty using platelet-rich plasma.

OBJECTIVE: Perforations of the tympanic membrane are treated with various surgical techniques and materials. This study aimed to determine the efficacy of platelet-rich plasma during underlay myringoplasty. METHODS: The study included 40 patients. Autologous platelet-rich plasma was applied in-between temporalis fascia graft and tympanic membrane remnant during underlay myringoplasty in group 1 (n = 20). The outcome was evaluated after three months and compared with group 2 (n = 20), a control group that underwent routine underlay tympanoplasty. RESULTS: After three months' follow up, graft uptake was 95 per cent in group 1 and 85 per cent in group 2 (p < 0.03). Mean hearing threshold gain was 18.62 dB in group 1 and 13.15 dB in group 2. This difference was statistically significant (p < 0.01). CONCLUSION: Platelet-rich plasma, with its ease of preparation technique, availability, low cost, autologous nature and good graft uptake rate, justifies its use in tympanoplasty type I procedures.

Systematic review: safety of mesalazine in ulcerative colitis.

BACKGROUND: Mesalazine is the most commonly prescribed medication for mild to moderate ulcerative colitis. It is generally well tolerated with some reported side effects. AIM: To summarise adverse drug events to mesalazine and recommend techniques for management. Furthermore, to determine if there is a dose-dependent relationship between high (>2.4 g/day) vs low dosing (≤2.4 g/day) and occurrence of adverse drug events. METHODS: A literature search for relevant studies from inception to 1 December 2017 of the MEDLINE database was conducted. Two reviewers screened all titles identified. Data obtained from randomised controlled trials was used to estimate incidence rates of each adverse event. Two reviewers independently assessed methodological risk of bias and performed data extraction. RESULTS: 3581 articles were initially considered. Of these, 3573 were screened, 622 reviewed and 91 included. Adverse events attributed to mesalazine included inflammatory reactions, pancreatitis, cardiotoxicity, hepatotoxicity, musculoskeletal complaints, respiratory symptoms, nephropathies and sexual dysfunction. There does not appear to be a dose-dependent relationship of mesalazine and occurrence of adverse events. CONCLUSION: Patients on mesalazine should be monitored for worsening of ulcerative colitis and development of new onset organ dysfunction. High-dose mesalazine appears to have similar safety profile as low dose, and is not associated with greater risk of adverse events. Prior to placing a patient on mesalazine, baseline liver and renal function should be evaluated. Renal function should be periodically assessed, whereas other testing should be performed depending on development of symptoms.

Role of local application of autologous platelet-rich plasma in the management of pressure ulcers in spinal cord injury patients.

STUDY DESIGN: Prospective clinical case series. OBJECTIVES: The objective of this study is to evaluate the local application of platelet-rich plasma (PRP) in relation to pressure ulcers (PrUs) healing on one PrU (case) versus saline dressing on another PrU (control) in the same patient. SETTING: Tertiary Level Care Centre, India. METHODS: Twenty-five spinal cord injury patients with at least two PrUs were included. All 25 PrUs (case) were grade IV, and PrUs (control) were grade II (n=11), grade IV (n=10) and grade III in 4 patients. Evaluation of PrU healing was done by measuring wound surface area, Pressure Ulcer Scale for Healing (PUSH), biopsy and clinical examination. RESULTS: Statistically significant decrease in mean PUSH scores of PrUs (case) (t=6.13, P<0.000) and PrUs (control) (t=3.98, P=0.000) was observed after 5 weeks. The wound surface area of PrU (case) decreased significantly (t=4.98, P=0.000); however, the decrease was not significant (t=0.095, P=0.924) in PrUs (control). Majority of histopathological pictures of PrUs (case) showed necrosis and suppuration (56%) at the time of enrollment and well-formed granulation tissue and epithelialization (60%) at the 5th week. Twenty-four (96%) PrUs (case) improved and only 1 deteriorated with PRP therapy, whereas in control group 17 (68%) PrUs improved, 7 (28%) deteriorated and 1 wound showed no change. CONCLUSIONS: Advanced wound therapy using local applications of PRP seems to be a promising alternative to standard saline dressings in PrU healing. With the advantages of simple preparation, biocompatible safety, low cost and significant clinical effectiveness, it may be beneficial to study the effects of PRP in large-scale trials to validate it as an ideal therapy for enhanced wound healing in PrUs.

pH regulation of the kinetic stability of the lipase from Thermomyces lanuginosus.

Thermomyces lanuginosus lipase (TlL) is a kinetically stable protein, resistant toward both denaturation and refolding in the presence of the ionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant decyl maltoside (DecM). We investigate the pH dependence of this kinetic stability. At pH 8, TlL remains folded and enzymatically active at multimillimolar surfactant concentrations but fails to refold from the acid urea-denatured state at submillimolar concentrations of SDS and DecM, indicating a broad concentration range of kinetic trapping or hysteresis. At pH 8, very few SDS molecules bind to TlL. The hysteresis SDS concentration range shrinks when moving to pH 4-6; in this pH range, SDS binds as micellelike clusters. Although hysteresis can be eliminated by reducing disulfide bonds, destabilizing the native state, and lowering the unfolding activation barrier, SDS sensitivity is not directly linked to intrinsic kinetic stability [its resistance to the general chemical denaturant guanidinium chloride (GdmCl)], because TlL unfolds more slowly in GdmCl at pH 6.0 than at pH 8.0. However, the estimated net charge drops from approximately -12 to approximately -5 between pH 8 and 6. SDS denatures TlL at pH 6.0 by nucleating via a critical number of bound SDS molecules on the surface of native TlL to form clusters. These results imply that SDS sensitivity is connected to the availability of appropriately charged regions on the protein. We suggest that conformational rigidity is a necessary but not sufficient feature of SDS resistance, because this has to be combined with sufficient negative electrostatic potential to avoid extensive SDS binding.

Green chemistry approaches to leather tanning process for making chrome-free leather by unnatural amino acids.

In the present study, green and sustainable method or eco-friendly approaches to tanning process based on unnatural D-amino acids (D-AA)-aldehyde (Ald) as a substitute for chrome-free tanning has been attempted. The distribution of optically active D-AA in tanned leather, the hydrothermal stability, the mechanical properties and resistance to collagenolytic activity of tanned leather, the evaluation of eco-friendly characteristics were investigated. Scanning electron microscopic (SEM) and Atomic force microscopic (AFM) analyses indicate the surface morphology and roughness, respectively, of the tanned leather collagen matrix. Shrinkage and Differential scanning calorimetric (DSC) analyses shows that the shrinkage temperature (T(s)) and denaturation temperature (T(d)) of tanned leather are related to the content of D-AA+Ald present in the leather matrix. It has been found that the T(s) of D-AA tanned leather is more than that of Ald tanned leather and also more or less equal to chrome tanned leather. Environmental impact assessment (EIA) shows that the developed process results in significant reduction in total solids content (TSC) and improves better biodegradability of organic compound present in the effluent compared to chrome tanning.

Comparative evaluation of platelet-rich plasma and guided tissue regeneration membrane in the healing of apicomarginal defects: a clinical study.

INTRODUCTION: The aim of the study was to compare the healing responses of platelet-rich plasma (PRP), PRP + a collagen sponge, and a collagen membrane used as guided tissue regeneration (GTR) materials for the treatment of apicomarginal defects. METHODS: Thirty patients with suppurative chronic apical periodontitis and apicomarginal communication were selected and allocated randomly into three groups according to the barrier technique to be used during periradicular surgery: the collagen membrane group, the PRP group, and the PRP + collagen sponge group. Clinical and radiographic measurements were determined at baseline and every 3 months after surgery up to 1 year. Cases were defined as healed when no clinical signs or symptoms were present, and radiographs showed complete or incomplete (scar tissue) healing of previous radiolucencies. RESULTS: The PRP and PRP + collagen sponge groups depicted 83.33% and 88.89% healing, respectively, in terms of combined clinical-radiographic healing as compared with 80% in the collagen membrane group. All the three treatments showed highly significant (P < .05) reductions in the periodontal pocket depth (PD), the clinical attachment level (CAL), the gingival margin position (GMP), the size of the periapical lesion, the percentage reduction of the periapical rarefactions, and periapical healing. No significant differences between the three groups were evident for these parameters (P > .05). CONCLUSIONS: GTR applied to apicomarginal defects using PRP or PRP + collagen sponge lead to similar enhancements of the clinical outcome of periradicular surgery in terms of periapical healing, gain of periodontal support, PD reduction, and PRP may be an alternative treatment for GTR membrane in the treatment of apicomarginal defects.

Characterization of native and denatured ricin using MALDI-TOF/MS.

Ricin is a toxic protein present in the seeds of castor bean plant. It can be inactivated by heat; therefore characterization of denatured ricin is essential to differentiate it from native ricin and to avoid any ambiguity in its identification. In this study, potential of mass spectrometry using MALDI—TOF/MS has been exploited to investigate the effects of heat treatment on ricin and spiked food matrices. The molecular weights of ricin, ricin A (A1 and A2) and B chain were found to be 62.8 kDa, 31.2 kDa, 32.5 kDa and 32 kDa respectively. The mass spectrum revealed a polypeptide chain of 11.1 kDa for denatured ricin. The peptide mass fingerprinting showed 24 peptides, six were common both in native and denatured ricin. The differentiating peptide at position 294—318 (m/z 934.533) was observed only in denatured ricin. The three selected marker peptides m/z 1013.6, 1310.7, 1728.9 are chosen for identification of ricin inactivated by heat in spiked apple juice and milk samples by immunocapture analysis. There is always a probability of denatured non— toxic ricin being confused with native (toxic) ricin to create unnecessary panic. Keeping this probability in mind, our study will be of immense value in minimising such risk.

Preparation and clinical evaluation of succinylated collagen punctal plugs in dry eye syndrome: a pilot study.

AIM: This is a pilot study of 10 eyes of 6 patients. This paper describes the preparation and clinical evaluation of succinylated collagen punctal plugs (SCPP) in the treatment of dry eye syndrome (DES). METHODS: SCPP were prepared from succinylated collagen with the exact dimensions of the punctum (length 1.5-2.5 mm, diameter 0.2-0.5 mm, water content between 50 and 55%). All the patients were clinically evaluated for best corrected visual acuity (BCVA), tear fluid levels (TFL), protein content, tear fluid osmolarity (TFO), fluorescence staining of the cornea and tear break-up time (TBUT) before and after punctal occlusion with SCPP. RESULTS: TFL improved among all the patients after punctal occlusion with SCPP. BCVA showed improvement in case 4 (right eye/left eye), case 5 (left eye) and case 6 (right eye), who had developed dry eyes due to environmental conditions. Protein content increased on day 7 in all the patients and gradually decreased. TFO decreased on days 3 and 5 in all patients after punctal occlusion with SCPP, and showed the same levels on day 14. TFL, PC, TFO and TBUT showed significant improvement in all the patients after punctal occlusion with SCPP. CONCLUSION: All patients experienced symptomatic relief after punctal occlusion with SCPP. There was no discomfort, foreign body sensation, plug extrusion, corneal aberration, infection, or formation of pyogenic granuloma with SCPP. SCPP stands as a promising alternative to other punctal plugs in the treatment of DES.

In vitro evaluation of antioxidants of fruit extract of Momordica charantia L. on fibroblasts and keratinocytes.

The antioxidant activity of the total aqueous extract (TAE) and total phenolic extract (TPE) of Momordica charantia fruits was assayed by radical-scavenging methods and cytoprotective effects on hydrogen peroxide (H(2)O(2))- and hypoxanthin-xanthin oxidase (HX-XO)-induced damage to rat cardiac fibroblasts (RCFs), NIH 3T3, and keratinocyte (A431). Cell viability was monitored by a 3-[4,5-dimethyltriazol-2-yl]-2,5-diphenyltretrazolium (MTT) assay. For fibroblasts, TPE at 200 and 300 microg/mL showed maximum and consistent cytoprotection against oxidants. The extract at 50 microg/mL also had significant and slightly protective effects on fibroblasts against H(2)O(2)- and HX-XO-induced damage, respectively. RCF was more tolerant toward the damage. For keratinocytes, a dose-dependent relationship of oxidant toxicity was only seen with H(2)O(2) but the protective action of the extract correlated with oxidant dosage. At 200 and 300 microg/mL TPE, cytoprotection was dose-dependent against oxidants. Extracts had no effect on HX-XO toxicity at 50 microg/mL. Pretreatment with both the extracts did not show any cytoprotection.

Evaluation of antimicrobial efficacy of herbal alternatives (Triphala and green tea polyphenols), MTAD, and 5% sodium hypochlorite against Enterococcus faecalis biofilm formed on tooth substrate: an in vitro study.

INTRODUCTION: The purpose of this study was to evaluate the antimicrobial efficacy of Triphala, green tea polyphenols (GTP), MTAD, and 5% sodium hypochlorite against E. faecalis biofilm formed on tooth substrate. METHODS: Extracted human teeth were biomechanically prepared, vertically sectioned, placed in the tissue culture wells exposing the root canal surface to E. faecalis to form a biofilm. At the end of the 3rd and 6th weeks all groups were treated for 10 minutes with the test solutions and control and were analyzed qualitatively and quantitatively. RESULTS: Qualitative assay with 3-week biofilm showed complete inhibition of bacterial growth with Triphala, MTAD and NaOCl, except GTP and saline, which showed presence of bacterial growth. In quantitative analysis, GTP- and saline-treated tooth samples have shown 1516 +/- 17.2 CFU/mL, 156.4 x 10(9) +/- 3.1 x 10(9) CFU/mL respectively. Qualitative assay with 6-week biofilm showed growth when treated with Triphala, GTP and MTAD whereas NaOCl has shown complete inhibition. All groups except NaOCl showed eight log reduction when compared to control when analyzed quantitatively. CONCLUSIONS: 5% sodium hypochlorite showed maximum antibacterial activity against E. Faecalis biofilm formed on tooth substrate. Triphala, green tea polyphenols and MTAD showed statistically significant antibacterial activity. The use of herbal alternatives as a root canal irrigant might prove to be advantageous considering the several undesirable characteristics of NaOCl.

Biocompatibility of choline salts as crosslinking agents for collagen based biomaterials.

A series of novel choline based salts, some of which can be described as ionic liquids, are prepared and evaluated for their biocompatibility; when combined with collagenous biomaterials they exhibit good cell viability and adhesion properties as required for biomedical implant applications.

Optimization of influential parameters for extracellular keratinase production by Bacillus subtilis (MTCC9102) in solid state fermentation using Horn meal--a biowaste management.

A Bacillus subtilis (MTCC9102) isolate was shown to produce significant amount of keratinase under optimized conditions in solid-state fermentation using Horn meal as a substrate. Optimized value for moisture, inoculum, and aeration were found to be 100% (v/w), 50% (v/w), and 150% (w/w), respectively, and the optimum nitrogen source was peptone and carbon source was dextrose. Maximum keratinolytic activity was observed at 48 h after incubation, and the optimum age (24 h) of inoculum was significant. The influence of cultivation temperature and initial pH of the medium on keratinase production revealed the optimum values for the temperature and pH as 37 degrees C and 7, respectively. Maximum keratinase activity of the crude extract was 15,972 U/mg/ml. These results indicate that this bacterial strain shows a high biotechnological potential for keratinase production in solid-state fermentation, and use of the horn meal as the substrate can be implemented for keratinous solid wastes management.

Fruit extracts of Momordica charantia potentiate glucose uptake and up-regulate Glut-4, PPAR gamma and PI3K.

ETHNOPHARMACOLOGICAL RELEVANCE: Momordica charantia fruit is a widely used traditional medicinal herb as, anti-diabetic, anti-HIV, anti-ulcer, anti-inflammatory, anti-leukemic, anti-microbial, and anti-tumor. AIMS OF STUDY: The present study is undertaken to investigate the possible mode of action of fruit extracts derived from Momordica charantia (MC) and study its pharmacological effects for controlling diabetic mellitus. Effects of aqueous and chloroform extracts of Momordica charantia fruit on glucose uptake and up-regulation of glucose transporter (Glut-4), peroxisome proliferator activator receptor gamma (PPAR gamma) and phosphatidylinositol-3 kinase (PI3K), were investigated to show its efficacy as a hypoglycaemic agent. MATERIALS AND METHODS: Dose dependent glucose uptake assay was performed on L6 myotubes using 2-deoxy-D-[1-(3)H] glucose. Up-regulatory effects of the extracts on the mRNA expression level of Glut-4, PPAR gamma and PI3K have been studied. RESULTS: The association of Momordica charantia with the aqueous and chloroform extracts of Momordica charantia fruit at 6 microg/ml has shown significant up-regulatory effect, respectively, by 3.6-, 2.8- and 3.8-fold on the battery of targets Glut-4, PPAR gamma and PI3K involved in glucose transport. The up-regulation of glucose uptake was comparable with insulin and rosiglitazone which was approximately 2-fold over the control. Moreover, the inhibitory effect of the cyclohexamide on Momordica charantia fruit extract mediated glucose uptake suggested the requirement of new protein synthesis for the enhanced glucose uptake. CONCLUSION: This study demonstrated the significance of Glut-4, PPAR gamma and PI3K up-regulation by Momordica charantia in augmenting the glucose uptake and homeostasis.

Evaluation of succinylated collagen bandage lenses in corneal healing by the expression of matrix metalloproteinases (MMP-2 and MMP-9) in tear fluid.

AIM: The aim of the study was to evaluate the efficacy of succinylated collagen bandage lenses (SCBL) in the healing of various corneal conditions. METHODS: Clinical evaluation of SCBL was carried out in patients with corneal ulcer (CU), recurrent corneal erosions (RCE), dry eyes (DE) and corneal lesion (CL). In each patient, corneal healing was studied by subjective clinical assessment such as pain, redness, watering, discomfort, irritation, foreign body sensation, biochemical analysis of tear fluid (TF) for protein content, expression of matrix metalloproteinases (MMPs) by gelatin zymography (GZ) and Western blotting (WB). In both GZ and WB bands were quantified and analyzed by gel documentation analyzer. RESULTS: Subjective clinical assessment of CU, RCE, DE and CL patients after treatment with SCBL showed significant reduction in the symptoms, patients felt comfortable with SCBL with no change in visual acuity, indicating complete transparency of SCBL. Protein content was very high on day 1 among all the patients, and it reduced gradually after treatment with SCBL signifying corneal healing. GZ of TF showed the expression of both MMP-2 and MMP-9 on day 3. There was significant reduction in MMP-2 and MMP-9 expression on day 7 in all cases, it decreased considerably on day 14 and was almost negligible on day 21 reflecting corneal healing with SCBL. CONCLUSION: Our study indicated that SCBL significantly reduces symptoms of irritation and discomfort in the cornea. It maintains visual acuity, controls inflammation and watering in the eye reflecting corneal healing in all cases studied by us. SCBL represents a promising alternative to other bandage lenses in corneal healing.

Clinical evaluation of succinylated collagen bandage lenses for ophthalmic applications.

AIM: To study whether succinylated collagen bandage lenses (SCBL) prepared from modified bovine collagen (succinylated collagen) can replace other bandage lenses presently employed to treat various corneal conditions like filamentary keratitis, dry eyes, recurrent corneal erosions, foreign body removal and epithelial trauma. METHODS: This observational case study included 32 patients (22 female and 10 male): 8 patients for filamentary keratitis (25%), 10 patients for dry eyes (31%), 4 patients for recurrent corneal erosions (13%), 7 patients for foreign body removal (22%) and 3 patients for epithelial trauma (9%). Their eyes were evaluated for biocompatibility, in vivo transparency, patient comfort, corneal fit, best corrected visual acuity (BCVA), tear fluid level and dissolution rate of SCBL. This was carried out over a 24-hour period of time. RESULTS: SCBL exhibited good transparency and remained transparent throughout the period of study (between 0 and 24 h) in the eyes of patients. SCBL did not cause any irritation, discomfort and foreign body sensation in the eye and eyes remained comfortable throughout the experiment. BCVA in the control group of patients was 1.00 (20/20). Mean (+/-SD) BCVA before inserting SCBL (in decimal equivalent) was 0.31 (20/60) +/- 0.18 (range 0.1- 0.66). BCVA (+/-SD) changed to 0.25 (20/80) +/- 0.18 4 h after the application of SCBL and 0.27 (20/70) +/- 0.18 24 h after the application of SCBL, with a safety index of 1.20. The mean (+/-SD) tear fluid level before application of SCBL was 11.9 +/- 5.39 h (range 3-24 mm) and changed to 13.9 +/- 5.68 h (range 5-28 mm) after 4 h of application of SCBL and 15.9 +/- 5.72 h (range 7-30 mm) after 24 h with a safety index of 13 mm. The mean (+/-SD) dissolution rate of SCBL in the control group of patients was 17.8 +/- 8.65 h (range 10-24 h) and the mean (+/-SD) dissolution rate in the experimental group was 22.2 +/- 9.29 h (range 10-24 h). We report the use of SCBL in various corneal conditions. CONCLUSION: The present study showed that SCBL has complete corneal fit and good comfort in human eyes. Transparency was maintained for a longer period along with fair visual acuity and improvement in tear fluid levels. The disadvantages of other bandage lenses presently used to treat various corneal conditions could be overcome by the use of SCBL lenses.

Alternative membrane protein conformations in alcohols.

Alcohols modulate the oligomerization of membrane proteins in lipid bilayers. This can occur indirectly by redistributing lateral membrane pressure in a manner which correlates with alcohol hydrophobicity. Here we investigate the direct impact of different alcohol-water mixtures on membrane protein stability and solubility, using the two detergent-solubilized alpha-helical membrane proteins DsbB and NhaA. Both proteins precipitate extensively at intermediate concentrations of alcohols, forming states with extensive (40-60%) beta-sheet structure and affinity for the fibril-specific dye thioflavin T, although atomic force microscopy images reveal layer-like and spherical deposits, possibly early stages in a fibrillation process trapped by strong hydrophobic contacts. At higher alcohol concentrations, both DsbB and NhaA are resolubilized and form non-native structures with increased (DsbB) or decreased (NhaA) helicity compared to the native state. The alternative conformational states cannot be returned to the functional native state upon dilution of alcohol. The efficiency of precipitation and the degree to which DsbB is destabilized at low alcohol concentrations show the same correlation with alcohol hydrophobicity. Thus, in addition to their effect on the membrane, alcohols perturb membrane proteins directly by solvating the hydrophobic regions of the protein. At intermediate concentrations, this perturbation exposes hydrophobic segments but does not provide sufficient solvation to avoid intermolecular association. Resolubilization requires a reduction in the relative dielectric constant below 65 in conjunction with specific properties of the individual alcohols. We conclude that alcohols provide access to a diversity of conformations for membrane proteins but are not a priori suitable for solution studies requiring reversible denaturation of monomeric proteins.

A novel method to measure oxygen permeability and transmissibility of contact lenses.

PURPOSE: The present paper describes an accurate and cost-effective method requiring simple equipment to measure the oxygen permeability and transmissibility of contact lenses. METHOD: The method involves accurate measurement of oxygen across the material by allowing the gas (oxygen) to pass through the lens material in a specially fabricated lens mould. The expelled gas is collected by dissolution in ethanol and the oxygen is measured by titration of the solvent. RESULT: This method is suitable for the measurement of oxygen permeability and transmissibility of contact lenses of varying thickness and different radii of curvature. It can measure Dk and Dk/t of collagen bandage lenses in both wet and dry conditions. CONCLUSION: The oxygen permeability and transmissibility values obtained by this method were compared with the oxygen permeability standard values of commercially available contact lenses and the results are summarised.

Using micellar mole fractions to assess membrane protein stability in mixed micelles.

The increased focus on the structural and physical properties of membrane proteins has made it critical to develop methods that provide a reliable estimate of membrane protein stability. A simple approach is to monitor the protein's conformational changes in mixed detergent systems, typically consisting of an anionic (denaturing) and non-ionic (non-denaturing) component. Linear correlations between, e.g., the melting temperature and the bulk mole fraction of the anionic component have been observed. However, a potential complication is that the bulk mole fraction is not identical to the mole fraction in the mixed micelle, which is the local environment experienced by the membrane protein. Here, we present an extensive analysis of the thermal stability of the membrane-integrated domain of the outer membrane protein AIDA in the presence of different mixed micelles. In the micelle system SDS-octyl-polyoxyethylene, the melting temperature in the absence of SDS extrapolates to 113 degrees C using bulk mole fractions. However, for mixed micelles involving short-chain detergents or phospholipids, the melting temperature calculated using bulk mole fractions reaches values up to several hundred degrees higher than 113 degrees C and can only be obtained by extrapolation over a narrow mole fraction interval. Furthermore, there is a non-linear relationship between the melting temperature and bulk mole fractions for mixed micelle systems involving cationic detergents (also denaturing). We show that if we instead use the micellar mole fraction as a parameter for denaturing detergent strength, we obtain linear correlations which extrapolate to more or less the same value of the melting temperature. There remains some scatter in the extrapolated values of the melting temperature in different binary systems, which suggest that additional micellar interactions may play a role. Nevertheless, in general terms, the mixed micellar composition is a good parameter to describe the membrane protein's microenvironment. Note, however, that for the mixed micelle system involving SDS and dodecyl maltoside, which has been used by several research groups to determine membrane protein stability, the estimate provided by bulk mole fraction leads to similar values as that of micellar mole fractions.