Search results for "Concentration."
showing 10 items of 1849 documents
Association between plasma ionized calcium and lactate concentration
1993
ISE are not suitable for the measurement of ionized calcium under clinical conditions when anions like acetate, lactate or malate are present in concentrations of about 5–10 mmol/l.
In-situ suspended aggregate microextraction: A sample preparation approach for the enrichment of organic compounds in aqueous solutions.
2015
Abstract This work presents in-situ suspended aggregate microextraction (iSAME) as a new and expedient sample preparation method. This new concept capitalizes on the general principles of in-situ solvent formation microextraction, in the sense that extraction is carried out in a supramolecular aggregate phase, which is formed in-situ in the sample through one-step process involving ion-association between a cationic surfactant and a benzene sulfonic acid derivative. The suspended aggregate containing the analytes is then collected in the form of a thin-film on the surface of a common filter paper by suction filtration. The entrapped analytes are released by completely dissolving the thin-fi…
Purification and characterization of the ?-β-hydroxybutyrate dehydrogenase from dromedary liver mitochondria
2001
Abstract d -β-Hydroxybutyrate dehydrogenase (BDH) (EC 1.1.1.30), a membrane enzyme, has been purified to homogeneity from dromedary ( Camelus dromedarius ) liver mitochondria. Our new purification method consisted of the solubilization of mitochondrial membranes by Triton X 100 and purification of BDH by two steps: DEAE-Sephacel and Phenyl-Sepharose. The molecular mass of the enzyme subunit size was 67 kDa. The purified enzyme is recognized by anti rat liver mitochondrial BDH antibodies. Furthermore, BDH activity was absolutely dependent upon phospholipids. BDH is also characterized by specific enzymatic parameters: an optimum pH of approximately 8 for the oxidation reaction, and approximat…
Activity of the dietary flavonoid, apigenin, against multidrug-resistant tumor cells as determined by pharmacogenomics and molecular docking
2015
Apigenin is a common dietary flavonoid with considerable cytotoxic activity in vitro and in vivo. Despite many mechanistic studies, less is known about resistance factors hampering apigenin's activity. We investigated the ATP-binding cassette (ABC) transporters BCRP/ABCG2, P-glycoprotein/ABCB1 and its close relative ABCB5. Multidrug-resistant cells overexpressing these ABC transporters were not cross-resistant toward apigenin. Moreover, apigenin inhibited not only P-glycoprotein but also BCRP by increasing cellular uptake of doxorubicin and synergistic inhibition of cell viability in combination with doxorubicin or docetaxel in multidrug-resistant cells. To perform in silico molecular docki…
Biological response of multicellular emt6 spheroids to exogenous lactate
1991
The influence of elevated lactate concentrations, as found in tumor microregions, on cellular growth, viability, and metabolic state was studied employing the multicellular spheroid model. Spheroids of EMT6/Ro cells were cultured at 37 degrees C in 5% or 20% (v/v) oxygen, using stirred media with various concentrations of exogenous lactate ranging from 0.0 mM (standard conditions) to 20.0 mM. Elevated concentrations of exogenous lactate led to a considerable decrease of the maximum spheroid diameter at growth saturation, e.g., for 20% O2 from around 1700 microns to 700 microns in 0.0 and 20.0 mM lactate respectively. Histological investigations showed that the thickness of the viable cell r…
R-Roscovitine (Seliciclib) prevents DNA damage-induced cyclin A1 upregulation and hinders non-homologous end-joining (NHEJ) DNA repair.
2010
Abstract Background CDK-inhibitors can diminish transcriptional levels of cell cycle-related cyclins through the inhibition of E2F family members and CDK7 and 9. Cyclin A1, an E2F-independent cyclin, is strongly upregulated under genotoxic conditions and functionally was shown to increase NHEJ activity. Cyclin A1 outcompetes with cyclin A2 for CDK2 binding, possibly redirecting its activity towards DNA repair. To see if we could therapeutically block this switch, we analyzed the effects of the CDK-inhibitor R-Roscovitine on the expression levels of cyclin A1 under genotoxic stress and observed subsequent DNA damage and repair mechanisms. Results We found that R-Roscovitine alone was unable …
Impact of Extracellular Acidity on the Activity of P-glycoprotein and the Cytotoxicity of Chemotherapeutic Drugs
2006
AbstractThe expression and activity of P-glycoprotein (pGP) play a role in the multidrug resistance of tumors. Because solid-growing tumors often show pronounced hypoxia or extracellular acidosis, this study attempted to analyze the impact of an acidic environment on the expression and activity of pGP and on the cytotoxicity of chemotherapeutic agents. For this, prostate carcinoma cells were exposed to an acidic extracellular environment (pH 6.6) for up to 24 hours. pGP activity was more than doubled after 3 to 6 hours of incubation in acidic medium, whereas cellular pGP expression remained constant, indicating that increased transport rate is the result of functional modulation. In paralle…
Resistance to diverse apoptotic triggers in multidrug resistant HL60 cells and its possible relationship to the expression of P-glycoprotein, Fas and…
2002
We studied the human HL60 leukemia cell line and its multidrug resistant (MDR) variant HL60R. In contrast to the HL60, HL60R showed an inability to undergo apoptosis from doxorubicin (Dox) or other different stimuli, including cisplatin, Fas ligation and serum withdrawal. HL60R cells lost surface Fas expression, but we found no evidence that Fas/FasL mediates the apoptotic effects of Dox in HL60. P-glycoprotein (P-gp) did not seem to play a major role as a specific inhibitor of apoptosis. In fact, the P-gp inhibitor verapamil reversed only partially the resistance to Dox-induced apoptosis of the MDR cells. In addition, it did not modify the rate of apoptosis induced from the other stimuli i…
Role of the tumor microenvironment in the activity and expression of the p-glycoprotein in human colon carcinoma cells.
2006
The metabolic microenvironment of solid tumors is characterized by an oxygen deficiency and increased anaerobic glycolysis leading to extracellular acidosis and ATP depletion, which in turn may affect other energy-dependent cellular pathways. Since many tumors overexpress active drug transporters (e.g. the p-glycoprotein) leading to a multidrug-resistant phenotype, this study analyzes the impact of the different aspects of the extracellular microenvironment (hypoxia and acidosis) on the activity and expression of the p-glycoprotein (pGP) in the human colon carcinoma cell line LS513. For up to 24 h cells were exposed to hypoxia (pO2<0.5 mmHg), an acidic extracellular environment (pH 6.6), or…
Genome-wide association analyses identify 18 new loci associated with serum urate concentrations
2013
Elevated serum urate concentrations can cause gout, a prevalent and painful inflammatory arthritis. By combining data from >140,000 individuals of European ancestry within the Global Urate Genetics Consortium (GUGC), we identified and replicated 28 genome-wide significant loci in association with serum urate concentrations (18 new regions in or near TRIM46, INHBB, SFMBT1, TMEM171, VEGFA, BAZ1B, PRKAG2, STC1, HNF4G, A1CF, ATXN2, UBE2Q2, IGF1R, NFAT5, MAF, HLF, ACVR1B-ACVRL1 and B3GNT4). Associations for many of the loci were of similar magnitude in individuals of non-European ancestry. We further characterized these loci for associations with gout, transcript expression and the fractional…