Search results for "Hydrogen-ion concentration"
showing 10 items of 769 documents
Design, synthesis and stimuli responsive gelation of novel stigmasterol-amino acid conjugates.
2020
Abstract An efficient synthesis of three novel stigmasterol-amino acid (glycine, l -leucine and l -phenylalanine) conjugates as stimuli responsive gelators is reported. The gelation properties of the prepared compounds were investigated in a variety of organic as well as aqueous solvents. The most striking finding of our investigation was that the hydrochloride salts of the prepared conjugates acted as gelators, whereas the neutral conjugates were either non-gelators or formed only a weak gel in anisole. The hydrochloride salts of stigmasteryl glycinate and l -leucinate form gels in n-alcohols (n = 4–10) and in ethane-1,2-diol, and that of stigmasteryl l -phenylalaninate forms gels in aroma…
DIFFERENTIAL SCANNING CALORIMETRY STUDY ON DRUG RELEASE FROM AN INULIN-BASED HYDROGEL AND ITS INTERACTION WITH A BIOMEMBRANE MODEL:pH AND LOADING EFF…
2008
Inulin has been derivatized with methacrylic anhydride (MA) and succinic anhydride (SA) to obtain a methacrylated/succinilated derivative (INU-MA-SA) able to produce a pH sensitive hydrogel after UV irradiation. The hydrogel was characterized and loaded with diflunisal (10.4, 17 and 24%, w/w) chosen as a model drug. The drug release from INU-MA-SA-based hydrogel to a biomembrane model made by unilamellar vesicles of dimyristoylphosphatidyl-choline (DMPC) was investigated at pH 4.0 and 7.4 by differential scanning calorimetry (DSC) that appears to be a suitable technique to follow the transfer kinetics of a drug from a controlled release system to a biomembrane model. The drug release from t…
Self-assembling and auto-crosslinkable hyaluronic acid hydrogels with a fibrillar structure
2008
Abstract A hyaluronic acid derivative bearing pendant l -benzoyl-cysteine portions (with a derivatization degree equal to 10 mol.%) was synthesized by linking N,N′-dibenzoyl- l -cystine to the polysaccharide and then reducing its disulfide bridge to thiol groups. The formation of π–π stacking interactions between the benzoyl moieties was studied by fluorescence spectroscopy as a function of polymer concentration and oxidation time. The efficiency of oxidation of thiol groups to disulfide bridges occurring in phosphate buffer pH 7.4, was determined by colorimetric assays. The hydrogel formed by means of oxidative crosslinking has shown the presence of fibrillar aggregates as detected by ligh…
Use of QSAR methods for predicting the chemiluminescent behaviour of organic compounds upon reaction with potassium permanganate in an acid medium
2009
In previous work, molecular connectivity computations were successfully used to predict the chemiluminescent behaviour of organic compounds upon reaction with common strong oxidants and the native fluorescence too; both of them in a liquid phase. The obtained results were used to develop new analytical procedures to the given compounds. For the first time, connectivity methods were used for a purely analytical purpose. In this work, we went deeper into the knowledge of direct chemiluminescence processes by using molecular connectivity in the form of QSAR methods to predict the chemiluminescence intensity produced by reactions between organic compounds (pharmaceuticals mainly) and potassium …
Ocean acidification affects fish spawning but not paternity at CO2 seeps
2016
Fish exhibit impaired sensory function and altered behaviour at levels of ocean acidification expected to occur owing to anthropogenic carbon dioxide emissions during this century. We provide the first evidence of the effects of ocean acidification on reproductive behaviour of fish in the wild. Satellite and sneaker male ocellated wrasse ( Symphodus ocellatus ) compete to fertilize eggs guarded by dominant nesting males. Key mating behaviours such as dominant male courtship and nest defence did not differ between sites with ambient versus elevated CO 2 concentrations. Dominant males did, however, experience significantly lower rates of pair spawning at elevated CO 2 levels. Despite the hig…
Rectal pH in children
1989
In an attempt to establish normal values for rectal pH in children, we have measured pH in 100 paediatric patients. Measurement of rectal pH was performed in 25 infants and 75 children (27 girls and 73 boys) using a monocrystalline antimony electrode. Rectal pH was 9.6 +/- 0.9 (mean +/- SD, range 7.2 to 12.1) and was independent of sex, age and nutrition. This wide range of rectal pH values offers a possible explanation for the widely scattered bioavailability of drugs administered by the rectal route. Mean rectal pH was considerably higher than that reported for adults; this unexpected alkalinity should be taken into account, when drug formulations are considered for rectal administration …
Noninvasive methods for the detection of upper and lower airway inflammation in atopic children
2006
Background Exhaled nitric oxide (FE NO ) and exhaled breath condensate (EBC) are noninvasive methods to assess inflammation. Objective To investigate the role of the FE NO and of the EBC pH and IL-5 levels in atopic children. Methods We evaluated oral and nasal FE NO and the pH and IL-5 of oral and nasal EBC in children with atopic dermatitis (AD; n=18), allergic rhinitis (AR; n=18), intermittent asthma (n = 21), moderate persistent asthma (n = 18), and healthy controls (HCs; n=16). Results Oral FE NO was significantly increased in asthma, whereas the nasal values were increased in AR and asthma in comparison with HCs. The pH of oral EBC was lower in AD and asthma than in AR and HCs, wherea…
Metabolism of tresperimus by rat aorta semicarbazide-sensitive amine oxidase (SSAO).
2002
Tresperimus (Cellimis), a new immunosuppressive agent, is mainly eliminated in the rat through metabolism, in which the oxidative deamination of the primary amine of the drug plays a major role. We have previously demonstrated in vivo the significant involvement of semicarbazide-sensitive amine oxidase (SSAO) in this reaction. Rat aorta, a tissue with one of the highest specific SSAO activities, was tested as a new in vitro model to elucidate tresperimus metabolism, using a combination of liquid chromatography/mass spectrometry (LC/MS) and high-performance liquid chromatography (HPLC) analyses. The metabolites resulting from the main metabolic pathway of the drug were formed in rat aorta ho…
A Hydrogel Based on a Polyaspartamide: Characterization and Evaluation of In-vivo Biocompatibility and Drug Release in the Rat
1997
Abstract This paper deals with the characterization of a new microparticulate hydrogel obtained by gamma irradiation of α,β-poly[N-(2-hydroxyethyl)-dl-aspartamide] (PHEA). When enzymatic digestion of PHEA hydrogel was evaluated using various concentrations of pepsin and α-chymotrypsin no degradation occurred within 24 h. In-vivo studies showed that this new material is biocompatible after oral administration to rats. PHEA hydrogel was also studied as a system for delivery of diflunisal, an anti-inflammatory drug. In-vitro release studies in simulated gastrointestinal juice (pH 1 or 6.8) showed that most of the drug was released at pH 6.8. In-vivo studies indicated that diflunisal-loaded PHE…
pH distributions in spontaneous and isotransplanted rat tumours.
1988
Spontaneous mammary tumours of the rat with various degrees of malignancy exhibit similar tissue pH distributions. The mean pH (+/- s.d.) of dysplasia is 7.05 +/- 0.20. In benign tumours the mean pH is 6.95 +/- 0.19 and in malignant tumours it is 6.94 +/- 0.19. In contrast, tumours with the same degree of malignancy but different histologies show different pH distributions. Benign tumours with a higher percentage of fibrous tissue exhibit less acidic pH values than those with larger portions of epithelial cells (delta pH = 0.38 pH units). The pH distribution in the benign tumours is independent of the tumour wet weight up to stages of very advanced growth. In the malignant tumours, a trend …