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PubMed1986

A microcomputer program for probit analysis of interleukin-2 (IL-2) titration data.

IL-2 activity is commonly estimated in cell culture supernatants by an IL-2-dependent cell proliferation assay. This method is both reproducible and sensitive. However, it often appears from the literature that statistical analysis of the titration data either is disregarded or, when performed, is based on statistically incorrect assumptions. The proposed method is based on the principle of biological assay by parallel lines as applied to probit analysis of quantitative responses. The procedure has been embodied in a simple and interactive computer program which automatically estimates the IL-2 concentration in the biological sample, in terms of U/ml, and provides its standard error and confidence limits. This program is also suitable for quantitative determination of other biologically active substances that show a sigmoid dose/response relationship.

Animals↗
PubMed1984

Amide proton titration shifts in bull seminal inhibitor IIA by two-dimensional correlated 1H nuclear magnetic resonance (COSY). Manifestation of conformational equilibria involving carboxylate groups.

Amide proton titration shifts in H2O solution of bull seminal inhibitor IIA were measured over the pH range from 3 to 6 using two-dimensional correlated spectroscopy. These data enabled characterization of the pKa values for the majority of the carboxylate groups in the protein. Two glutamate side-chains were found to form hydrogen bonds with their own backbone amide proton. Different temperature variations of the populations of these local, cyclic structure elements are indicated for the individual sites.

Amides↗
PubMed1990

Inhibition of DNA gyrase activity in an in vitro transcription-translation system stimulates gyrA expression in a DNA concentration dependent manner. Evidence for the involvement of factors which may be titrated.

Stimulation of gyrA expression in an in vitro transcription-translation system by novobiocin, a DNA gyrase inhibitor, depends on the DNA concentration in the extract. At low DNA concentrations (less than 20 micrograms/ml) we note significant stimulation (2 to 25 x) upon the addition of novobiocin; at high DNA concentrations, stimulation is minimal. This observation is not due to the limited capacity of the system to transcribe or relax DNA. Using an extract prepared from a novobiocin-resistant strain of Escherichia coli, we were able to show that DNA gyrase mediates the novobiocin-enhanced expression. In an experiment with a fixed level of a gyrA-lac template, we found that the addition of a second non-Lac template increased expression from the gyrA-lac template, while concomitantly decreasing the extent of novobiocin stimulation. These observations are consistent with an inhibitory factor that can be titrated by increasing the DNA concentration and whose effects are minimized when the DNA template is in a relaxed conformation. The results of a mixed-extract experiment using two extracts that differ in their activities and degrees of novobiocin stimulation are also consistent with an inhibitory factor that mediates the relaxation-induced stimulation of transcription.

DNA↗
PubMed1984

Human saliva and taste responses to acids varying in anions, titratable acidity, and pH.

Twenty subjects recorded perceived sourness of solutions of citric + fumaric and of citric + tartaric acids, at pH 3.5 and titratable acidity (TiA) of 4.0 g/l on a moving chart, while parotid saliva flow was recorded via a sialometer . Sourness intensity and flow were greater when citric was the minor acid than when it was dominant. Subjects varied widely in calculated volume of saliva reservoir, but not flow rate (time to 2/3 reservoir vol.). In tartaric-fumaric acid mixtures varying in pH (3.0-3.75) at a constant TiA of 4.0 g/l, and varying in TiA (3.7-4.6 g/l) at a constant pH of 3.5, sourness intensity and parotid flow increased with acidity and decreased with pH. However, eight subjects with a high flow (HF = 1.2 +/- 0.28 g/2 min) and nine subjects with a low flow (LF = 0.43 +/- 0.11 g/2 min) differed widely: (a) In response to variation in stimulus pH and TiA, HF demonstrated marked alteration in flow, but little change in sourness ; LF responded at a lower absolute level, but showed marked changes in sourness and little change in flow; (b) Salivary pH was higher and Na+ was three times greater for the HF than for the LF subjects; and (c) Salivary Ca++ showed a direct relationship with flow and pH among the HF, but an inverse relationship for the LF subjects.

Adult↗
PubMed1980

A comparison of carbon dioxide titration curves of arterial mixed venous and coronary sinus blood.

Two types of titration curve (log PCO2 vs. pH and whole blood [HCO3-] vs. pH) were obtained in anaesthetized dogs by altering FICO2. Both plots reveal a significant progressive decrease in slope from arterial(a) to mixed venous (v) to coronary sinus (cs) blood. Lines drawn between corresponding points on the arterial and mixed venous or coronary sinus curves have slopes determined by the Respiratory Exchange Ratio (R) and are called R lines. Differences in slope between arterial and venous (v or cs) curves may be due to changes in blood flow or of delivery of CO2 to the blood. The former is indicated by constant R values at different CO2 tensions whilst the latter is a reflection of changing R values due to fluctuations in CO2 stores. The myocardium is not an important store for CO2 but CO2 has a profound effect on coronary blood flow and it is this that causes the difference in a-cs slopes. The reverse is true for skeletal muscle where the charging and discharging of CO2 stores brings about the difference in a-v slopes.

Acid-Base Equilibrium↗
PubMed1986

Ventilatory regulation of extracellular pH in crayfish exposed to changes in water titration alkalinity and NaCl concentration.

The mechanisms of extracellular pH regulation were studied in normoxic crayfish Astacus leptodactylus during changes in water ionic composition at 13 degrees C. In artificial waters all ambient physico-chemical properties were controlled. Ventilatory changes and the time course of hemolymph acid-base balance, ABB, were followed after a decrease of water titration alkalinity, TAw, from 4 to 2 meq X L-1 simultaneously associated with either an increase of NaCl concentration, [NaCl]w, from 0.5 to 5 mmol X L-1, or a decrease of [NaCl]w, from 0.5 to 0.15 mmol X L-1. The ABB changes were characterized by a hypercapnic acidosis attributable to the decrease of TAw. Depending on the simultaneous change of [NaCl]w, two different mechanisms of compensation were observed. When [NaCl]w increased, the compensation was metabolic: the ventilatory requirement, VW X MO2-1, did not vary. When [NaCl]w decreased, the compensation was ventilatory: VW X MO2-1 doubled. It is concluded that in water-breathers ventilation, contrary to what is generally accepted, can play a role in extracellular ABB regulation.

Acid-Base Equilibrium↗
PubMed1983

The use of infectivity titrations for measurement of the viability of Entamoeba histolytica after cryopreservation.

An infectivity titration technique is described for the measurement of the viability of Entamoeba histolytica. Using this method an optimal cryopreservation technique has been developed. When amoebae from young cultures were equilibrated with 7.5% dimethylsulphoxide for 15 minutes at 37 degrees C, cooled to -100 degrees C at 1 degree C per minute, and stored in liquid nitrogen, 1 to 2% regularly survived after thawing rapidly at 37 degrees C and, on occasions, 10 to 12% survived.

Animals↗
PubMed1983

Evaluation and standardization of polymerized ragweed extracts by chromatography, radioimmunoassay inhibition, and end point cutaneous titration.

The standardization procedures for polymerized ragweed (PRW) must evaluate activity of PRW with assessments that differ from those used for standard unmodified extracts. This is because PRW allergens are different from conventional ragweed extracts in that they are much greater in average molecular weight and much lower in allergenicity for equivalent immunogenicity. We have evaluated seven samples of PRW for three parameters: allergenicity as determined by cutaneous end point titration, molecular weight distribution as determined by Sephadex G-200 chromatography, and availability of antigen E (AgE) determinants as measured by the ability of an extract to inhibit AgE binding to antibody by using a modification of the Farr technique. The skin test titers and molecular weight profiles provide information as to the safety of a PRW preparation and antigen-binding inhibitory activity gives information about allergenicity and immunogenicity. Appropriate limits may be set for each of these parameters to standardize PRW for clinical use.

Allergens↗
PubMed1991

Indirect evidence of bronchial inflammation assessed by titration of inflammatory mediators in BAL fluid of patients with asthma.

Bronchial inflammation is a characteristic of asthma that may be examined indirectly by bronchoalveolar lavage (BAL). Nine normal individuals were compared with 38 age-matched adults with asthma of variable severity to appreciate the importance of cell activation in the severity of asthma. The severity of asthma was appreciated by the clinical score of Aas and the pulmonary function of the patients. FEV1 ranged between 35% and 130% of predicted. The indirect activation of eosinophils (EOSs), mast cells, fibroblasts, and neutrophils was examined by the titration of eosinophil cationic protein (ECP), tryptase, hyaluronan (HA), and myeloperoxidase (MPO) by radioimmunoassay in BAL fluid (BALF) and cytology of BALF. In the adults with asthma, there was a significantly increased number of EOSs and a significantly increased level of all mediators but MPO. MPO levels were increased in seven patients only; three of these patients were previous smokers. Only ECP and HA levels were significantly correlated with the severity of asthma. These results demonstrate EOSs, mast cells, and fibroblasts are activated in asthma, whereas the involvement of neutrophils is less clear. There was a significant correlation between ECP and HA levels, suggesting a common activation of EOSs and fibroblasts.

Adult↗
PubMed1982

[Correlations between immunoenzymatic test, neutralization test and fluorescent focus reduction test in rabies antibody titration].

Three methods have been used and compared for the detection and titration of antibodies in the serum of humans receiving post-exposure treatment with tissue culture inactivated rabies vaccines: mouse seroneutralization test, fluorescent focus reduction test and immunoenzymatic test. Results have shown that the fluorescent focus reduction test has a sensitivity and specificity which are equivalent to the mouse seroneutralization test with the advantage of giving results in 30 hr instead of 21 days, and that the immunoenzymatic test which avoids the use of laboratory animals and/or cell cultures, and which gives results in 5 hr, may advantageously replace the neutralization methods, particularly for the testing of large numbers of sera.

Antibodies↗
PubMedDate not supplied

Effects of synergistic anions on the proton magnetic resonance spectra and pH titration of histidinyl side chains in the C-terminal half-molecule of ovotransferrin.

High-resolution proton magnetic resonance spectra of the C-terminal half-molecule of ovotransferrin (OTf/2C) clearly resolve the C(2)H resonances of the five histidinyl residues in the protein. Formation of the Ga(III)OTf/2C(anion) ternary complexes results in different chemical shift and titration behaviors for certain C(2)H resonances in the carbonato, oxalato, and malonato complexes. The pKa' of the imidazole group involved in a proton relay with the synergistic anion and a water of hydration appears to be anion independent. Thus the initial attack of a proton on the ternary complex appears to be at a ligand other than the anion or anion-binding imidazole group.

Anions↗
PubMed1986

The determination of binding constants with a differential thermal and potentiometric titration apparatus. II. EDTA, EGTA and calcium.

A differential pH and thermal titrimeter has been used to determine the ionization constants of EDTA and EGTA as well as their calcium complexes. The intrinsic heat of binding is a constant for the pH range 2-11.5 for both substances and is found to be -5.4 kcal mol for EDTA and -7.9 kcal mol-1 for EGTA. The binding constants evaluated by fitting to the potentiometric curves and expressed as the log are 10.25 and 11.0, respectively. These values compare reasonably well to those reported in the literature. We have proposed that the binding of calcium occurs even at acid pH based on the pH drop observed at pH 2 when calcium is added, the reversibility of the thermal and the potentiometric curves, the lack of hysteresis upon rapid titration, the constancy of the intrinsic heat of binding and fitting of the entire potentiometric curves using the appropriate binding constants.

Calcium↗
PubMedDate not supplied

Fast titration experiments using heat conduction microcalorimeters.

Thermopile heat conduction calorimeters normally have high time constants. Multistep titration experiments involving fast processes may then require several hours to perform. It is demonstrated that such experiments can be conducted about 10 times faster, without loss of accuracy, by use of a "dynamic correction method". For a new small vessel thermopile conduction calorimeter, injections can be made at 1.5-min intervals.

Calorimetry↗
PubMed1994

Heat conduction calorimeters: time constants, sensitivity and fast titration experiments.

Seven heat conduction calorimeters have been evaluated in terms of sensitivity and thermal response time. The use of a dynamic method to correct for the thermal inertia of the calorimeter is shown to reduce by one order of magnitude the time required to conduct a stepwise titration experiment involving a fast reaction. The ability to determine association constants of strong 1:1 complexes has been evaluated in terms of the precision of determining thermal energy.

Calorimetry↗
PubMed1980

A simple and rapid microassay for the titration of human respiratory syncytial virus.

A microassay, using tissue culture microplates for the titration of human respiratory syncytial virus by syncytium formation, is described. Virus titers obtained agreed well with those obtained in a larger assay system; the microassay, however, is more rapid and economical. Large numbers of virus samples are easily and rapidly processed as the assay necessitates an incubation period of only three days.

Animals↗
PubMed1984

A comparison of three methods for titration of poliovirus vaccines.

Two methods for in vitro endpoint titration of poliovirus--the roller tube and the microtitration assay--were compared with each other and with the plaque assay, using secondary vervet monkey kidney cells and Vero cells as indicators. The roller tube method is the most reliable under difficult working conditions, but is otherwise cumbersome and expensive. The microtitre method is the most economical and the plaque assay the most sensitive. By suspending freshly trypsinized indicator cells with the virus dilutions before planting, it was possible to simplify the microtitre method considerably. The sensitivity of the plaque assay was improved for Vero cells by absorbing the virus onto freshly planted monolayers. The method was scaled down to a semi-micro level by using 24-well cell culture trays. The slower rate of plaque development under a low calcium overlay medium facilitated a more accurate plaque count.

Animals↗
PubMed1988

A novel EBNA-1 titration method and putative anti-EBNA-1 protein.

A novel and rapid EBNA-1 titration method has been developed which uses immunoprecipitation of specific DNA-protein complexes with EBNA-1-positive serum. The method is more sensitive than the conventional immunofluorescence method and has potential value as a diagnostic reagent for clinical laboratories. TPA induction of putative anti-EBNA-1 protein of cellular origin is discussed, which may play a key role for the shift from latent to lytic replication of EBV.

Antibodies, Viral↗
PubMed1988

Rapid titration of bovine, caprine and human RS virus by a micro-immunoperoxidase assay using a monoclonal antibody and a permissive ovine kidney cell line.

An indirect immunoperoxidase micro-assay, using a continuous cell line derived from ovine kidney cells (OK) and a previously characterized monoclonal antibody (7C2), specific for an exposed and highly conserved epitope of the fusion protein of different strains of RS virus, was used advantageously to rapidly titrate bovine, caprine and human strains of RSV by either quantal (TCID50) or plaque forming assays. Virus titers, obtained in less than 36 h, were in agreement with those obtained by the conventional plaque assays which required an incubation period of 4 days or more. This assay is also applicable to micro-neutralization of fusion inhibition assays for testing serum or screening monoclonal antibodies.

Animals↗