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PubMed1998

Accurate titration of avidin and streptavidin with biotin-fluorophore conjugates in complex, colored biofluids.

A new fluorimetric assay is presented for the specific and reliable quantitation of >/=2 nM avidin and streptavidin. The assay is based on pronounced changes in the fluorescence properties of commercial fluorescein-biotin, or of a newly synthesized biotin-poly(ethylene glycol)-pyrene conjugate, which occur upon binding to avidin and streptavidin. Accurate measurement of (strept)avidin in complex, colored biofluids, such as crude egg white or serum relies on a simple titration protocol. Only occasional recalibration of the reagent solution is required. Due to these merits the proposed assay is particularly suited for rapid measurement of few samples on short notice, for functional control of (strept)avidin-containing reagents after storage, and for the monitoring of (strept)avidin concentrations in large scale processes.

Animals↗
PubMed1977

[Detection and titration of anti-tetanus antibodies by passive hemagglutination].

Human red cells O Rh + are coated with purified tetanus toxoid, by means of chromic chloride as coupling agent. With this reagent and by passive haemagglutination technique, antitetanus antibodies can be automatically screened and titrated in blood donnors plasmas, on Groupamatic equipments. Comparative results of three techniques: counter immunoelectrophoresis; manual passive haemagglutination; automatic passive haemagglutination are given, 4, 92 percent among the 1.219 tested blood donnors plasmas have an antibody greater than or equal to 5 U.I., 16, 24 percent have a titre between 1 and 5 U.I.

Antibodies, Bacterial↗
PubMed2003

Buprenorphine dosing regime for inpatient heroin withdrawal: a symptom-triggered dose titration study.

The study aimed to identify the range of buprenorphine doses required to comfortably alleviate symptoms in patients undergoing inpatient heroin withdrawal using a symptom-triggered titration dosing regime, and to identify the patient characteristics that impact upon the buprenorphine dose requirements. The study was conducted in two Australian inpatient withdrawal units, recruiting 63 dependent, injecting heroin users with no recent methadone treatment, dependence on other drugs, or other active medical or psychiatric conditions. In a single (patient) blinded case series, placebo or 2 mg sublingual buprenorphine tablets was administered four times a day according to severity of withdrawal (assessed with Subjective Opiate Withdrawal Scale). Up to 16 mg buprenorphine was available over the first 4 days of the admission, up to 8 mg on day 5, and placebo continued until day 6. Thirty-two subjects completed the dosing regime, with mean (+/-S.D.) daily doses of 3.8+/-2.8 on day 1, 5.8+/-3.2 on day 2, 4.8+/-3.3 on day 3, 2.3+/-2.6 on day 4, 0.8+/-1.3 on day 5, and a total dose of 17.4+/-9.7. Higher buprenorphine doses were required by those patients with more severe psychosocial dysfunction, women, those with more frequent heroin use, and those with more severe dependence on heroin at intake. A dosing regime using sublingual buprenorphine tablets for short inpatient heroin withdrawal is proposed.

Adolescent↗
PubMed1998

Identification of Btr-regulated genes using a titration assay. Search for a role for this transcriptional regulator in the growth and virulence of Bordetella pertussis.

Bordetella pertussis is the causative agent of the respiratory disease pertussis or whopoping cough. Btr, an oxygen-responsive transcriptional regulator of B. pertussis, is homologous to the FNR protein of E. coli. Using a murine respiratory model, we observed in the present study that Btr is important in growth and survival of B. pertussis in vivo. A titration assay was developed that identified genes containing Btr binding sites including B. pertussis sodB and btr, E. coli aspA and a new B. pertussis gene, brg1. The brg1 gene encodes a protein similar to the LysR family of transcriptional regulators and its expression is activated threefold by Btr under anaerobic growth conditions but unaffected by Btr aerobically. The nucleotide sequence flanking brg1 encodes proteins with similarity to various metabolic enzymes. Putative overlapping promoters and a Btr binding site (FNR box) were identified in the DNA sequence between brg1 and the adjacent genes. These intervening sequences may represent sites for regulation by Btr and Brg1.

Amino Acid Sequence↗
PubMed2001

Development of a novel dosage form for intramuscular injection of titrated extract of Centella asiatica in a mixed micellar system.

Titrated extract of Centella asiatica (TECA), a drug used in treating systemic scleroderma, is poorly water-soluble. A conventional dosage form for the intramuscular injection of TECA, propylene glycol (PG)-based TECA solution, causes severe pain after intramuscular injection. To improve the solubility of TECA and reduce pain after injection, mixed micellar systems composed of 10% surfactant mixture (Tween 20 and Tween 85) and 90% phosphate-buffered saline, pH 7.0 (PBS) were prepared. As the ratio of Tween 20 to Tween 85 increased from 0:10 to 10:0, the solubility of TECA in the mixed micellar systems increased from 7- to 26-fold compared to that in PBS (pH 7.0). The droplet size of micelles gradually decreased with the increasing ratio of Tween 20 to Tween 85 from 0:10 to 4:6, followed by an abrupt decrease in size above the ratio of 6:4. Furthermore, the micellar systems prepared with Tween 20 and Tween 85 at the ratio of 6:4, 8:2 or 10:0 could solubilize TECA more than 10 mg/ml and the resultant droplet sizes were less than 2 microm. No significant changes were observed in the droplet sizes and asiaticoside contents in these micellar formulations during storage, indicating these systems are stable for at least 60 days. Their osmotic pressures were remarkably lower than those of PG-based TECA solution and similar to that of saline solution, irrespective of dilution ratios. Most importantly, they markedly reduced the number of writhes compared with PG-based TECA solution after injection to mice. All of these results suggest that these three TECA micellar formulations prepared with Tween 20 and Tween 85 improved the solubility of TECA and reduced pain following injection, possibly due to the decrease in osmotic pressure. Thus, these micellar formulations composed of optimum ratios of Tween 20 and Tween 85 may have a potential as dosage forms for the intramuscular injection of a poorly water-soluble TECA.

Animals↗
PubMed2000

Determination of the pKa values of beta-blockers by automated potentiometric titrations.

The acid-base equilibrium constants of the beta-blockers atenolol, oxprenolol, timolol and labetalol were determined by automated potentiometric titrations. The pKa values were obtained in water-rich or water methanol medium (20% MeOH) to obviate the solubility problems associated with the compounds. The initial estimates of pKa values were obtained from Gran's method and then, were refined by the NYTIT and ZETA versions of the LETAGROP computer program. The resultant values were 9.4 (I = 0.1 M KCl, 20% methanol) for atenolol, 9.6 (I = 0.1 M KCl) for oxprenolol, 9.4 (I = 0.1 M KCl, 20% methanol) for timolol and 7.4 and 9.4 (I = 0.1 M KCl) for labetalol. The potentiometric method was found to be accurate and easily applicable. The operational criteria for applying the methodology are indicated.

Adrenergic beta-Antagonists↗
PubMed2002

Quantitation of vitamin C content in herbal juice using direct titration.

Vitamin C content in fresh and freeze-dried herbal juice, such as guava (Psidium guajava Linn.) emblic myrobolan (Phyllanthus embica Linn.), lemon (Citrus aurantifollia Swing), sweet pepper (Capsicum annuum Linn.) Garcinia schomburgkiana Pierre and passion fruit (Passiflora laurifoia Linn.) was determined by direct titration with iodine. The method showed excellent linearity (r2>0.99) over the concentration ranges tested (100-500% of the amount found in the juice samples), good precision (R.S.D.<1.5%) and recovery (>97%). The limit of detection and limit of quantitation were 2.2 and 7.3 mg, respectively. The amount of vitamin C found were 80.1 mg/100 g for guava, 226.0 mg/100 g for emblic myrobolan, 52.8 mg/100 g for sweet pepper, 39.1 mg/100 g for passion fruit, 10.5 mg/100 g for lemon and 4.6 mg/100 g for G. schomburgkiana. The stability of vitamin C during the first 4 weeks was remarkably improved after freeze-dried process. The percent reductions of vitamin C after freeze-dried process were 41.4 and 20.4% for guava and emblic myrobolan, respectively. After 8 weeks, the freeze-dried samples contained only traces amount of vitamin C tested by thin layer chromatography.

Ascorbic Acid↗
PubMed1998

[Pressure-controlled mechanical ventilation: a simplified titration method of the extrinsic positive expiratory pressure].

OBJECTIVES: Extrinsic positive end-expiratory pressure (PEEPe) may improve gas distribution within the lungs, induce alveolar recruitment or, conversely, produce pulmonary overdistension, and modify the respiratory impedance. Under pressure-controlled mechanical ventilation (PCV) this phenomenon modifies the minute ventilation and the dynamic compliance of the respiratory system (Crs,dyn). This study was aimed to assess the incidence of a significant gain in Crs,dyn under the effect of PEEPe during PCV. STUDY DESIGN: Prospective, open, descriptive, case series study. PATIENTS: Surgical intensive care unit patients, under sedation, neuromuscular blockade and PCV because of severe hypoxaemia (ARDS or acute lung injury). METHODS: Four incremental levels of PEEPe (4 to 16 cmH2O) of 30 minute duration were applied. Crs,dyn, and PaO2/FIO2 were recorded at the end of each level of PEEPe. The resulting gain in Crs,dyn was calculated and considered as significant if it was greater than the upper limit of confidence (at 99.8%) of the statistical distribution of all the recorded gains. RESULTS: Thirty patients were included, median and extreme values (within brackets) of PaO2/FIO2 of 117 [53-230] and Crs,dyn without PEEPe of 29 [14.3-46.8] mL.cmH2O-1. Among the 120 recorded gains, a gain in Crs,dyn was found significant at least once in 15 tests of PEEPe out of 30. Within the two groups of patients, the increase in PaO2/FIO2 with incremental PEEPe was similar. The levels of PEEPe producing the greatest increase in Crs,dyn were not correlated with the increase in PaO2/FIO2. CONCLUSION: In 50% of the studied patients a significant gain in Crs,dyn was found, allowing a less traumatic PCV. These results suggest the clinical usefulness of this method of titration of PEEPe, which requires neither specific devices nor a disconnection of the patient.

Adult↗
PubMed2000

A titrated morphine analgesic regimen comparing substance users and non-users with AIDS-related pain.

To compare morphine dosage and effectiveness in AIDS patients with/without prior substance use and pain, a prospective, open-label case series lasting 3-18 days was conducted in both outpatients and inpatients at major pain service teaching programs. Forty-four patients, 13 with prior drug use history, who had pain associated with HIV infection or its treatment were administered sustained-release morphine (SRM) every 12 hours. The dose was titrated to pain relief for a period of > or =3 consecutive days (associated with < or =2 immediate-release morphine tablets per 24 hours), or until the patient discontinued from the study or completed 18 study days. Forty-four patients were enrolled (13 with a prior drug use history). Forty were evaluable for an intent-to-treat analgesia, including 11 with a drug use history. Twenty-four (6 users) completed this study. Former users and non-users were similar in demographics, baseline pain intensities, causes of pain, discontinuation, quality of life, and acceptability of therapy. Pain intensity decreased by > or =50% in both groups (P < or = 0.0001). To identify a stable dose, the dose of SRM more than doubled in former users and rose by 31% in non-users (mean final dose 177.4 mg and 84.9 mg, respectively) (P = 0.0018). Immediate-release morphine decreased in both; former users required more (P = 0.0006). These data suggest the utility of morphine for AIDS-related pain. Patients with a prior drug use history benefited but required substantially more morphine.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Methadone: outpatient titration and monitoring strategies in cancer patients.

Methadone can be an effective drug for cancer pain but it can also be difficult to use safely. It has been recommended that rotation to methadone from other opioids be undertaken in a hospital setting. The purpose of the study was to characterize the safety, toxicities, and outcomes of outpatient rotation to methadone for severe cancer pain in a heavily pretreated cohort of cancer patients. Data were collected through a retrospective review of consecutive patients from a tertiary level cancer pain clinic. Twenty-nine patients were rotated to methadone, 13 (45%) due to opioid toxicity and 16 (55%) because of either cost or difficulty swallowing their prior opioid. Eleven of 29 patients (38%) failed methadone due to rapidly progressive cancer, dose-limiting side effects, or other reasons, but the other patients were successfully rotated to methadone. Pain usually improved following rotation to methadone, but drowsiness from methadone was common. On average, it took 32 days to successfully rotate to methadone in the outpatient setting. Cancer patients with advanced disease and severe pain can be safely and effectively rotated to methadone in the outpatient setting. It takes considerably longer to stabilize these patients than patients on lower doses of opioid or those titrated in the inpatient setting. A careful monitoring system is needed to screen for evidence of toxicity.

Analgesics, Opioid↗
PubMed1999

[Rapid relief, with little risk: titration of morphine].

Several years after the introduction of morphine for pain control, its use in pediatrics is limited by the fear of side effects. "Titration" represents a new way of management with a faster pain relief, and low risk of narcotic induced complication, the doses of morphine being self limited to the minimal pain relieving dosage. It consists in administering small doses of morphine every few minutes (10 in intravenous treatment or 30 orally) until total disappearance of pain; the total amount necessary for four hours is the sum of the initial dose and all the additional doses.

Administration, Oral↗
PubMed1994

Inhibition of Semliki Forest virus multiplication in L-cells by combinations of interferon and ribavirin as measured by plaque titration and direct enzyme immunoassay.

Inhibition of Semliki Forest virus (SFV) multiplication in L-cell monolayers by combinations of mouse interferon (IFN) and ribavirin was measured by plaque titration and by direct enzyme immunoassay of SFV in L-cells. When critically inhibitory quantities of IFN and ribavirin were combined, an additive inhibitory effect was observed in either assay.

Animals↗
PubMed1989

Evaluation of different calculation methods for anti-HBs titration.

Anti-HBs titre calculations should be standardized to make comparison between various vaccination programmes and between immunogenicity tests in animals more meaningful. For this purpose, we compared four methods of titre calculation in human and animal sera and in the IgM and IgG fractions of these sera. The four calculation methods are parallel line bioassay, Hollinger method, RIA units and regression-calibration curve. From our results, the following can be concluded: The titration curves of anti-HBs/IgM, anti-HBs/IgG and of animal sera do not always run parallel to the WHO standard curve. Thus, the objective quantification of these anti-HBs cannot be obtained with the WHO standard. The Hollinger method and the RIA units method are identical within the range S/P less than 1. They only differ by a factor of 4. Only dilutions giving results in the linear part of the dose-response curve should be considered for titre calculations. The mean of the results for different dilutions should be used to determine the titre. Within the restrictions mentioned, comparable results were obtained with the four methods.

Animals↗
PubMed2000

Clinical impact of hypnotic-titration guidelines based on EEG bispectral index (BIS) monitoring during routine anesthetic care.

STUDY OBJECTIVES: To examine the impact on perioperative care of routine Bispectral Index (BIS) monitoring during general anesthesia throughout an entire operating room (OR) suite. DESIGN: Open, observational trial with retrospective analysis of guideline performance. Data were analyzed from 1,552 adult patients receiving general anesthesia with surgical times of at least 1 hour and who were extubated by postanesthesia care unit (PACU) discharge. Staff were trained using a simple decision matrix, which integrated BIS titration goals with anesthetic management. Unmonitored patients were compared to either BIS-monitored patients or to performance subgroups based on BIS measurements recorded during anesthetic maintenance ("deep", BIS < 50; "target", 50-65; "light", >65). SETTING: Large, urban academic/trauma center. MEASUREMENTS AND MAIN RESULTS: Demographic profiles of all groups and subgroups were similar. Anesthetic emergence, recovery times, and volatile drug use were significantly shortened or reduced only when BIS values were maintained between 50 and 65. Extubation time from end of surgery decreased by 2.1 minutes from 5.7+/-7 (37%); OR exit time decreased by 2.2 minutes from 9.3+/-6 (24%); eligibility for phase 1 PACU discharge decreased by 4 minutes from 22+/-42 (23%); and actual PACU discharge decreased by 15 minutes from 130+/-78 (7%). PACU extubation frequency decreased from 6.9% to 2.6%. Modest decreases in total intraoperative drug use were noted with an increase in PACU analgesic administration. CONCLUSIONS: Routine application of BIS monitoring throughout an OR suite impacted clinical outcome only if guideline targets were met. BIS values within the last 30 minutes of surgery were not predictive of emergence or recovery. Hypnotic maintenance at BIS < 50 did not confer any clinical advantage over unmonitored cases. Anesthetic maintenance at BIS values between 50 and 65 was associated with shortened emergence and recovery from general anesthesia.

Adult↗
PubMed1998

Induction of anesthesia by titration of eltanolone compared with thiopental and etomidate for coronary artery bypass grafting.

STUDY OBJECTIVE: To evaluate whether induction of anesthesia with eltanolone in coronary artery bypass graft (CABG) patients is associated with greater hemodynamic stability than either thiopental sodium or etomidate. DESIGN: Randomized, controlled study. SETTING: University hospital. PATIENTS: 75 ASA physical status III and IV patients scheduled for elective CABG over 18 years of age, with left ventricular ejection fraction over 30%. INTERVENTIONS: The participants were prospectively randomized into three groups, each group consisting of 25 patients. Anesthesia was induced by titration of either eltanolone, thiopental sodium, or etomidate. The end point was "loss of verbal contact." MEASUREMENTS AND MAIN RESULTS: Hemodynamic variables were recorded in the awake state, 2 minutes after induction, after administration of fentanyl 0.01 mg/kg, and 2 and 5 minutes after intubation. After induction of anesthesia, cardiac index (CI) decreased from 2.6 +/- 0.5 to 2.2 +/- 0.5 Lxmin-1xm-2 in the eltanolone group and remained at this value throughout the study period in contrast to the control groups. After fentanyl was given, mean arterial pressure was significantly lower in the case of eltanolone (69 +/- 15 mmHg) compared with thiopental (81 +/- 19 mmHg) and etomidate (84 +/- 18 mmHg). Mean arterial pressure remained significantly lower at the points of measurement after intubation. Two minutes after intubation, CI was likewise significantly lower in the eltanolone group (2.2 +/- 0.4 Lxmin-1xm-2) compared with the thiopental group (2.7 +/- 0.7 Lxmin-1xm-2). CONCLUSIONS: Eltanolone produces more hemodynamic depression compared with etomidate and thiopental when administered in combination with fentanyl 10 micrograms/kg.

Aged↗
PubMed2001

Protein structure information from mass spectrometry? Selective titration of arginine residues by sulfonates.

Noncovalently bound complexes between basic sites of peptides/proteins and sulfonates are studied using Matrix Assisted Laser Desorption/Ionization (MALDI) Mass Spectrometry. Reactive sulfonate dyes such as Cibacron Blue F3G-A are known to bind to protonated amino groups on the exterior of a protein. In this work, we examine a wide range of other sulfonates with distinctly simpler structure and more predictable reactivity. Naphthalene-sulfonic acid derivatives were found to bind to arginine only, as opposed to expected binding to all basic sites (Arg, Lys and His). Detailed control experiments were designed to unambigously confirm this selectivity and to rule out nonspecific adduct formation in the gas phase. The data show that the number of complex adducts found equals the number of accessible arginine sites on the surface of folded peptides and proteins, plus the N-terminus. Lys and His are not complexed nor are buried residues with hindered access. MALDI-MS can therefore provide fast information related to the exposed surface of these biomolecules. Additional titration experiments with 1-anilino-naphthalene-8-sulfonic acid (ANS) revealed that this fluorescent dye, which was often hypothesized to bind to so-called molten globule states of proteins, behaved exactly like all other naphthalene-sulfonic acids. ANS binding thus occurs largely through the sulfonate group.

Journal Article↗
PubMed1996

Sensing the heat: the application of isothermal titration calorimetry to thermodynamic studies of biomolecular interactions.

Biomolecular interactions can be defined by combining thermodynamic data on the energetic properties of the interaction with high-resolution structural data. The development of high sensitivity isothermal titration calorimetric equipment provides a dramatic advance in the gathering of thermodynamic data, and the interactions between biological macromolecules can now be described with unprecedented accuracy.

Calorimetry↗
PubMed2005

Comparison of manual and homogenizer methods for preparation of tick-derived stabilates of Theileria parva: equivalence testing using an in vitro titration model.

Theileria parva sporozoite stabilates are used in the infection and treatment method of immunization, a widely accepted control option for East Coast fever in cattle. T. parva sporozoites are extracted from infected adult Rhipicephalus appendiculatus ticks either manually, using a pestle and a mortar, or by use of an electric homogenizer. A comparison of the two methods as a function of stabilate infectivity has never been documented. This study was designed to provide a quantitative comparison of stabilates produced by the two methods. The approach was to prepare batches of stabilate by both methods and then subject them to in vitro titration. Equivalence testing was then performed on the average effective doses (ED). The ratio of infective sporozoites yielded by the two methods was found to be 1.14 in favour of the manually ground stabilate with an upper limit of the 95% confidence interval equal to 1.3. We conclude that the choice of method rests more on costs, available infrastructure and standardization than on which method produces a richer sporozoite stabilate.

Animals↗