Search results for "Availability"

The effect of chitosan on the bioaccessibility and intestinal permeability of acyclovir

2019

Chitosan is object of pharmaceutical research as a candidate permeability enhancer. However, chitosan was recently shown to reduce the oral bioavailability of acyclovir in humans. The effect of chitosan on two processes determining the oral bioavailability of acyclovir, bioaccessibility and intestinal absorption, was now investigated. Acyclovir's bioaccessibility was studied using the dynamic TNO gastro-Intestinal Model (TIM-1). Four epithelial models were used for permeability experiments: a Caco-2 cell model in absence and presence of mucus and both rat and porcine excised intestinal segments. Study concentrations of acyclovir (0.8 g/l) and chitosan (1.6 g/l and 4 g/l) were in line with t…

Experimental Studies on the Influence of Surfactants on Intestinal Absorption of Drugs Cefadroxil as model drug and sodium taurocholate as natural mo…

2011

The influence of the natural bile acid surfactant sodium taurocholate (CAS 81-24-3) on colic and duodenal (i.e. the proximal third of the small intestine) absorption of cefadroxil (CAS 50370-12-2) was studied using the in situ rat gut technique, and compared with the effect of sodium lauryl sulfate (CAS 151-21-3), the most widely used synthetic anionic surfactant. Previously, the stability, compatibility, and micelle-solubilization characteristics of taurocholate were assessed in order to correct, when necessary, the absorption results. White the passive absorption rate constants (kf, h-1) determined in colon in the presence of increasing lauryl sulfate concentrations showed an asymptotic v…

Preparation and Characterisation of Alendronate-Loaded Chitosan Microparticles Obtained Through the Spray Drying Technique

2009

Microparticles of chitosan (CHT) containing alendronate sodium (AL) were prepared in four drug:polymer ratios (1:1, 1:2, 1:4, 1:6) using the spray drying technique. The efficiency of the method was evaluated by determining production yield (about 70 %) and microencapsulation efficiency, which was almost 100 % in the case of all four of the formulations studied. Particles had a mean size of between 3.6 and 4.6 microm, and a near-spherical shape. The formulations with the highest content of AL (drug:polymer ratio 1:1 and 1:2) showed an asymmetrical distribution of particles, which were larger in size, and had a higher proportion of irregular particles than the other formulations. FT-IR analys…

Combined effects of thermal conditions and food availability on thermal tolerance of the marine bivalve, Perna viridis

2018

Abstract Organisms can mitigate the effects of long term variation in environmental conditions through acclimation, which involves changes in various physiological responses. To elucidate the possible effects of temperature and food concentrations on acclimation capacity, physiological responses of the mussel, Perna viridis, were measured after individuals were held for six weeks under varying temperatures and food availability. Warm-acclimated mussels experiencing higher food levels had significantly greater upper thermal limits than those maintained on lower food levels. In contrast, the upper thermal limits of cold-acclimated mussels were not affected by food levels. For warm-acclimated …

The occurrence and bioavailability of retene and resin acids in sediments of a lake receiving BKME (bleached kraft mill effluent)

1999

Retene (7-isopropyl-1-methylphenantrene) is an alkyl substituted PAH derived primarily from bacterial aromatization of abietic type resin acids. Retene has been shown to induce cytochrome P450 1A in rainbow trout whereas e.g. dehydroabietic acid does not induce it. We analysed resin acids and retene in sediments from seven sites receiving pulp and paper mill effluents from 4 mills, and from two reference sites. All mills have employed treatment of waste waters by activated sludge. The highest concentration of retene measured in sediment was 1600 μg/g d.w. (11 700 μg/g organic carbon, OC) while the highest concentration of resin acids was 1500 μg/g d.w. (9 300 μg/g OC). Downstream from the p…

Sediment-associated retene bioavailability of sediment-associated retene to an oligochaete wormlumbriculus variegatus

2001

The bioavailability of retene spiked to two sediment concentrations (50 and 200 µg/g dry weight) was measured in long-term (28-day) bioaccumulation tests performed on the oligochaeteLumbriculus variegatus Muller. Three sediment organic carbon (SOC) concentrations (1.1, 3.0, 23.0% of dry weight) were used. Growth and reproduction, used as endpoints, indicated that retene was chronically nontoxic at the concentrations employed. Retene was clearly bioavailable, but bioaccumulated about 100 times less in the SOC-rich (23.0%) sediment than in the other two (SOC <3.0%). At the lower retene concentration, retene in the worms was undetectable in the high-SOC sediment. Based on final retene present …

Bioavailability of minerals in foods

2015

The Respiratory Potential of Oxygen: A New Quantity to Characterize State, Effects and Bio-Availability of the Gas in Organism

1992

A number of quantities are known which enable to characterize the state of oxygen in blood, for instance: the concentration, which means the physically solved mass per volume; or the content, which comprises the whole mass per volume irrespective of the molecular state; or capacity, which is the chemically bound mass of oxygen per volume and, relatively, the saturation, or the oxygen partial pressure. These various quantities may be divided into two types: the mass-related and the not-mass-related ones.

Data availability impact on integrated modelling reliability throughout identifiability analysis

2009

Endothelin-1-Mediated Drug Resistance in EGFR-Mutant Non-Small Cell Lung Carcinoma.

2020

Abstract Progression on therapy in non-small cell lung carcinoma (NSCLC) is often evaluated radiographically, however, image-based evaluation of said therapies may not distinguish disease progression due to intrinsic tumor drug resistance or inefficient tumor penetration of the drugs. Here we report that the inhibition of mutated EGFR promotes the secretion of a potent vasoconstrictor, endothelin-1 (EDN1), which continues to increase as the cells become resistant with a mesenchymal phenotype. As EDN1 and its receptor (EDNR) is linked to cancer progression, EDNR-antagonists have been evaluated in several clinical trials with disappointing results. These trials were based on a hypothesis that…