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At least 37 records · Page 2Linked to original sources
PubMed2003

[Large-scale real-time titration of green-fluorescence-protein-marked recombinant retrovirus: comparison with standard titration method].

OBJECTIVE: To compare large-scale real-time titration method (LaSRT) with standard titration method by flow cytometry (FACS) for determining the titers of green-fluorescence-protein (GFP)-marked recombinant retrovirus. METHODS: (1) Standard titration method: NIH3T3 cells were inoculated at 2x10(5) /well in 6-well plate, and after cell culture for 12 h, 0.5 ml, 50 microl and 5 microl GFP-marked recombinant retrovirus (n=3) were respectively used to infect the cells, with the final concentration of polybrene being 8 microg/ml. Forty-eight hours later, the cells were treated with trypsin and assayed for the positive rate of GFP by means of FACS. When the positive rate was lower than 10%, the titer was calculated according to the equation: virus titer (TU/ml) =2x10(5)xGFP positive rate/volume of virus stock solution used. (2) LaSRT method: The cells were inoculated at 5,000 cells/well in a 96-well plate, and after cell culture for 12 h, 90 microl/well complete culture medium was used with 8 microg/ml polybrene and 10% newborn bovine serum, 10 microl virus was added into the first well, and ten-fold dilution of the previous virus-containing solution was performed before the virus was added into the next well (8 wells in each group, altogether 3 groups). Forty-eight hours later, inverted fluorescence microscope was used to observe the fluorescence-positive cells in each well. The virus titer was calculated according to the equation: virus titer (TU/ml) =mx10(n+1), where n is the serial number of the reference well, and m the number of positive cells. (3) LaSRT was used to study the influence of freezing/thawing on the titers of recombinant retroviruses. RESULTS: The virus titer obtained with standard method by FACS was (1.54+/-0.38)x10(6) TU/ml, and that of LaSRT was (1.33+/-0.57)x10(6) TU/ml (P>0.05). After one cycle of freezing/thawing, the virus titer dropped to (18.1+/-9.9)% (n=7). CONCLUSION: LaSRT is more rapid and convenient as well as easier to determine the virus titer compared with standard method, and no significant difference is found between the two titration methods.

Animals↗
PubMed1985

Generalized theory for two-phase ion-pair and complexometric titrations. I. Two-phase titrations without side reactions.

A systematic theoretical treatment of the two-phase titration based on ion-pair and metal-complex formation is presented. Equations for the titration curve, accuracy, equivalence point and choice of the indicator are derived. Much attention is paid to the parameters determining the 'titratability' viz. extraction constant, distribution constant, phase volume ratio and the concentration of the analyte. Special attention is given to the role of intermediate ion-pair and metal-complex formation in the aqueous phase. The ion-pair formation in aqueous solution is examined closer by means of the relationship between the association constant in water, the degree of dissociation of the ion pair (alpha) and the concentration of the counter ion. The merits of this theoretical treatment are illustrated with literature examples.

Chemical Phenomena↗
PubMed2005

Standardization of a neutralizing anti-vaccinia antibodies titration method: an essential step for titration of vaccinia immunoglobulins and smallpox vaccines evaluation.

The possibility of mass population vaccination with smallpox vaccine implies the development of anti-vaccinia immunoglobulins for the treatment of severe side effects following vaccination. We have chosen to develop and validate the "gold standard method" (plaque reduction neutralization assay) to titrate neutralizing anti-vaccinia antibodies in two different French laboratories belonging to the Department of Defense (CRSSA) and to the French Health Products Safety Agency (Afssaps). The results of precision, linearity and accuracy of the method led to consider the method as validated. In parallel, we have prepared and lyophilized a pool of anti-vaccinia plasma samples issued from a unique donor and qualified this preparation versus the first British standard to use it as an in-house standard with a titer of 25 international units (IU). This work will allow to titrate, in IU, sera from vaccinated persons in order (i) to titrate purified anti-vaccinia immunoglobulin preparations for vaccine severe side effect treatments; (ii) to investigate the level of neutralizing antibodies in the general population; and (iii) to investigate clinical trials of new generation smallpox vaccines. In the future, this will allow comparability of studies on either smallpox vaccines or on the serological status of the population.

Animals↗
PubMed1975

Titration of tetanus antitoxin by passive hemagglutination. I. Titration of guinea-pig antitoxins at various periods of immunization.

An improved technique for passive hemagglutination (HA) for titration of tetanus antitoxin was described. The use of highly purified tetanus toxoid and of improved diluent increased the specificity and reproducibility of the test. Several hundreds of specimens of guinea-pig serum taken at various stages of immunization were titrated by HA and toxin neutralization (NT) in mice. The ratio of HA to NT titers varied significantly depending on the immunization stage; higher at early stages and lower at later stages. The high HA/NT ratio was not due to the IgM antitoxin, which is very rare in guinea pigs. The variation in discrepancy between HA and NT titers decreased considerably by grouping the serum specimens with respect to the stage of immunization. Thus, it is possible to predict the in vivo titer of a tetanus antitoxin accurately enough for clinical study. The HA test may be useful as an alternative method for titrating tetanus antitoxin in the field trials. Moreover, it can be used for the study of characteristics of antitoxins.

Animals↗
PubMed1985

Affinity gel titration: quantitative analysis of the binding equilibrium between immobilized protein and free ligand by a continuous titration procedure.

A new method, called affinity gel titration, for analyzing the specific interaction between an immobilized protein and a ligand molecule is presented. Only one or two experimental runs permit the determination of not only the equilibrium constant but also the amount of immobilized protein. A suspension of the immobilized protein on agarose gel beads is confined in a constant volume mixing cell. A solution of a specific ligand molecule of constant concentration is introduced into the cell so that its concentration in the cell increases continuously (as in a mixing chamber for forming a convex gradient). The correlation between the concentration of the ligand in the efflux and the cumulative volume of the efflux can be analyzed either by regression to a theoretical curve or by a graphical method. Specific binding of p-aminobenzamidine to immobilized Streptomyces griseus trypsin was studied by this method. The dissociation constant and the amount of active trypsin were determined. The values obtained were in good agreement with the inhibition constant obtained by a kinetic experiment with free trypsin and with the amount of active site measured by using p-nitrophenyl p'-guanidinobenzoate, respectively. A single run of the titration procedure could be completed within 1 h.

Autoanalysis↗
PubMed2005

Differential potentiometric titration: development of a methodology for determining the point of zero charge of metal (hydr)oxides by one titration curve.

A new methodology is presented, called differential potentiometric titration (DPT), which allows the determination of the point of zero charge (pzc) of metal (hydr)oxides using only one potentiometric curve. By performing extensive simulations of potentiometric titrations for various model (hydr)oxides, we found that an inflection point in a H+(cons,surf) versus pH potentiometric curve (H+(cons,surf): hydrogen ions consumed on the surface of the (hydr)oxide) and a peak in the corresponding differential curve, dH+(cons,surf)/dpH versus pH, appear at a pH equal to the pzc assumed for a model (hydr)oxide. This distinguishable peak appears at the same position irrespective of the surface ionization and the interfacial model adopted as well as the assumed ionic strength. It was found that the aforementioned peak also appears in the high-resolution differential potentiometric curves experimentally determined for four oxides (SiO2, TiO2, gamma-Al2O3, and MgO) that are widely used in various environmental and other technological applications. The application of DPT to the above-mentioned oxides provided practically the same pzc values as the corresponding ones achieved by using four different techniques as well as the corresponding isoelectric point (iep) values determined by microelectrophoresis. Differences between the pzc and iep values determined using various techniques in the case of MgO were attributed to the increasing dissolution of this oxide as pH decreases and the adsorption of cations (Mg2+, Na+) on the MgO/electrolytic solution interface.

Adsorption↗
PubMed1980

Bone CO2-titration curves in acute hypercapnia obtained with a modified titration technique.

Bone CO2-titration curves were obtained in mature rats weighing 500-600 g. Animals were exposed for one hour to 1, 3, 5, 10, or 15% CO2 in air. Measurements of bone CO2, were made using a modified titrimetric analysis on fresh and oven-dried samples of paired rat femurs. A manometric method was used for comparison. Arterial blood samples were obtained for measurements of partial pressure of CO2 in arterial blood (PaCO2). Within the range of environmental CO2 concentrations studied, a linear relationship was observed between the PaCO2 and the increment in fresh bone CO2 content. This relationship is defined by the equation: delta fresh bone CO2 (mmol/kg) = 61.8 +/- 0.68 PaCO2. The CO2 increment was confined to a heat-labile, presumably soluble pool comprising 10.5% of the total bone CO2 content. No change in the water content of the bone was observed as a result of acute CO2 exposure. The results of this study demonstrate the rapid in vivo CO2 uptake of bone in response to exposure to increased CO2 levels.

Acute Disease↗
PubMed2003

Labour induction at term--a randomised trial comparing Foley catheter plus titrated oral misoprostol solution, titrated oral misoprostol solution alone, and dinoprostone.

OBJECTIVES: To compare three methods of labour induction. DESIGN: Randomised controlled trial. SETTING: Academic hospitals in Johannesburg, South Africa. SUBJECTS: Women with intact membranes due for induction of labour. METHOD: Randomised, sealed opaque envelopes were used to allocate women to labour induction with extra-amniotic Foley catheter/titrated oral misoprostol solution (N = 174), titrated oral misoprostol solution alone (N = 176), or vaginal dinoprostone (N = 176). Misoprostol was dissolved in water and 20-40 g was given 2-hourly. OUTCOME MEASURES: These were failure to deliver vaginally within 24 hours, additional measures for induction or augmentation of labour, analgesia, and maternal and fetal complications. RESULTS: In the Foley catheter group, misoprostol was required in all but 1 case. Failure to deliver vaginally within 24 hours was similar for the three groups (79/174 v. 70/176 v. 70/176 respectively). Labour augmentation, caesarean section and instrumental delivery were used somewhat more frequently in the Foley/misoprostol group than in the misoprostol alone group, but these differences were not statistically significant. More analgesia was used in the Foley catheter/misoprostol group than in the misoprostol group (64/172 v. 46/175). Side-effects and neonatal complications were similar for the three groups. CONCLUSIONS: Use of extra-amniotic Foley catheter placement showed no measurable benefits over the use of oral misoprostol alone, or vaginal dinoprostone.

Administration, Intravaginal↗