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PubMed1953

Inhibition of influenza virus multiplication by alkyl derivatives of benzimidazole. I. Kinetic aspects of inhibition by 2,5-dimethylbenzimidazole as measured by infectivity titrations.

At a concentration of 0.0026 M, 2,5-dimethylbenzimidazole caused a number of alterations in the first cycle of multiplication of influenza B virus, Lee strain, in chorioallantoic membrane cultures in vitro. As determined by infectivity titrations in ovo on the membrane per se, the following alterations were observed: The duration of the latent period was increased by 80 per cent. The rate of increase in titer during the incremental period was somewhat decreased. The yield of virus was decreased by about 99 per cent. When the compound was added to membrane cultures at various periods before or after inoculation with the virus, the following findings were obtained: On addition before or along with the virus, the substance caused about 99 per cent inhibition of multiplication. When added during the first 2 hours after inoculation, the compound caused inhibition of a degree which was inversely proportional to the time of addition. When added 3 to 8 hours after inoculation, the substance caused about 80 per cent inhibition. When added after the end of the latent period, no definite inhibition was obtained in the first cycle of multiplication. These results are interpreted as indicating that 2,5-dimethylbenzimidazole acts by reducing the rate of biosynthetic mechanisms necessary for the reproduction of influenza virus particles.

Benzimidazoles↗
PubMed1950

The significance of regression line slope changes in the quantitative titration of complement components.

The hypothesis is discussed that dissociable complexes are formed between elements of a test complement (C') and the reagent used to titrate it for a particular component. Calculations are presented which demonstrate that such complex formation may give considerable changes in slopes of percentage hemolysis-log dose regression lines obtained with mixtures of C' and reagent. It is shown that marked change of slope may occur with relatively little change in the value of the 50 per cent intercept.

Complement System Proteins↗
PubMed2003

Forced oscillation technique in the sleep apnoea/hypopnoea syndrome: identification of respiratory events and nasal continuous positive airway pressure titration.

Sleep breathing disorders (SBD) are related to obstructions resulting from repetitive narrowing and closure of the pharyngeal airway. Their diagnoses and treatment are critically dependent on an accurate identification of and discrimination between types of respiratory events. However, these disorders have been diagnosed using indirect or invasive measurements, which resulted in serious doubts concerning the correct evaluation of breathing events. The forced oscillation technique (FOT) has recently been suggested as a clinical tool able to accurately and non-invasively quantify respiratory obstruction during sleep. The present study investigates the morphology of the impedance signal during different sleep respiratory events and evaluates the ability of impedance measurements in providing adequate nasal continuous positive airway pressure (nCPAP) titration. The results evidenced characteristic patterns in impedance signal morphology that are useful in the identification and classification of abnormal respiratory events. Moreover, significantly higher impedance values were obtained during apnoea and hypopnoea events when compared with normal values (p < 0.01). Studies using impedance measurements to adjust nCPAP showed a significant reduction (p < 0.01) of abnormal respiratory events, and a consequent normalization of the patients. These findings support the use of the FOT as a versatile clinic diagnostic tool helping SBD diagnosis and treatment.

Airway Resistance↗
PubMed2003

Response to methylphenidate in children with attention deficit hyperactivity disorder and manic symptoms in the multimodal treatment study of children with attention deficit hyperactivity disorder titration trial.

OBJECTIVE: Recent reports raise concern that children with attention deficit hyperactivity disorder (ADHD) and some manic symptoms may worsen with stimulant treatment. This study examines the response to methylphenidate in such children. METHODS: Data from children participating in the 1-month methylphenidate titration trial of the Multimodal Treatment Study of Children with ADHD were reanalyzed by dividing the sample into children with and without some manic symptoms. Two "mania proxies" were constructed using items from the Diagnostic Interview Schedule for Children (DISC) or the Child Behavior Checklist (CBCL). Treatment response and side effects are compared between participants with and without proxies. RESULTS: Thirty-two (11%) and 29 (10%) participants fulfilled criteria for the CBCL mania proxy and DISC mania proxy, respectively. Presence or absence of either proxy did not predict a greater or lesser response or side effects. CONCLUSION: Findings suggest that children with ADHD and manic symptoms respond robustly to methylphenidate during the first month of treatment and that these children are not more likely to have an adverse response to methylphenidate. Further research is needed to explore how such children will respond during long-term treatment. Clinicians should not a priori avoid stimulants in children with ADHD and some manic symptoms.

Attention Deficit Disorder with Hyperactivity↗
PubMed2004

Opioid dose titration for severe cancer pain: a systematic evidence-based review.

Dosing strategies to achieve rapid analgesia in patients with severe or crescendo cancer pain are important. A systematic review of research trials for treatment of severe or crescendo cancer pain was conducted; nine studies were identified. Eight trials were prospective; two were randomized between different dosing strategies. Dosing frequency predicted onset to analgesia regardless of baseline opioid dose. None of the trials were associated with evidence of respiratory depression. The studies all suffered significant methodological problems limiting broad conclusions. Until better data exist, opioid dose titration for severe/crescendo pain will be guided by expert opinion and experience.

Analgesics, Opioid↗
PubMed1996

Characterization of 911: a new helper cell line for the titration and propagation of early region 1-deleted adenoviral vectors.

Currently, the preferred host for the production of early region-1 (E1)-deleted recombinant adenoviruses (rAdV) is cell line 293, which was generated by transformation of human embryonic kidney cells by sheared adenovirus 5 (Ad5) DNA. To develop alternative hosts for the production of rAdV, we generated adenovirus-transformed human cell lines by transformation of human embryonic retinoblasts (HER) with a plasmid containing base pairs 79-5789 of the Ad5 genome. One of the established HER cell lines, which we called 911, exhibited favorable growth characteristics and was chosen for further study. This cell line is demonstrated to have several characteristics in common with the well-known 293 cell line: The 911 cell line is highly transfectable, and exhibits similar frequencies of homologous recombination. However, it has additional characteristics that make it a useful alternative for 293. The 911 cells perform particularly well in plaque assays. Upon infection with E1-deleted adenoviruses, plaques become apparent in monolayers of 911 cells already after 3-4 days versus 4-10 days in monolayers of 293 cells, thereby reducing the time required for quantitative plaque assays. Furthermore, yields of E1-deleted adenovirus vectors up to three times as high as those achieved with 293 cells can be obtained with 911 cells. Finally, the Ad5-DNA content of the 911 cell line is completely known. These features make the 911 cell line a useful alternative for the construction, propagation, and titration of E1-deleted recombinant adenoviruses.

Adenovirus E1 Proteins↗
PubMed1998

A tetrazolium-based colorimetric assay for titration of neutralizing antibodies against vaccinia virus.

A colorimetric assay for titration of neutralizing antibodies against vaccinia virus was developed. The test is based on the ability of live cells in culture to reduce the yellow tetrazolium salt MTT (thiazolyl-blue), to its blue formazan derivative. Antisera from individuals vaccinated with vaccinia virus against smallpox were serially diluted, incubated with 100 plaque-forming units (PFU) of vaccinia virus for 1 hour at 37 degrees C, and then transferred to a 96-well plate containing monolayers of B-SC-1 cells. After incubation for 3 to 4 days at 37 degrees C, when more than 80% of the control infected cultures exhibited high degree of cytopathogenic effect, MTT was added. The absorbance of the formazan formed and extracted by dimethylsulfoxide was read at 492 nm by an automatic microplate spectrophotometer. A good correlation was found between the results obtained using this newly developed method and those of the plaque-reduction assay.

Antibodies, Viral↗
PubMed1997

Evaluation of a new protamine titration method to assay heparin in whole blood and plasma.

When unfractionated heparin is used for therapeutic anticoagulation, the heparin effect must be monitored to avoid thrombotic or hemorrhagic complications. The ability of a factor Xa inhibition (XaI) assay was compared with that of a low-level heparin protamine titration (LLHPT) assay to measure the concentration of heparin after heparin was added in vitro to specimens of plasma and whole blood. Heparin effect on the activated partial thromboplastin time also was assessed in the same specimens. The XaI and LLHPT assays had comparable precision and provided linear results over a wide range of heparin concentrations. Both assays slightly underestimated the total amount of heparin added to the specimens. The most rapid test was the whole blood LLHPT assay; this test therefore may be useful for bedside monitoring of heparin. A significant disadvantage of the LLHPT assay was the large sample size required to perform it. These results provide in vitro evidence that the XaI and LLHPT assays can provide equally precise monitoring of heparin concentration.

Anticoagulants↗
PubMed1979

Comparison of the chloride electrode and gravimetric chloride titration sweat tests.

The chloride electrode sweat test and gravimetric chloride titration technic are compared. The two technics gave comparable mean values, ogives, equivalent points, and overlap for patients with cystic fibrosis and healthy subjects. As a single test with either technic has an unacceptable risk for false-positive or false-negative results, tests should always be done in pairs. A statistical interpretation technic based on prevalence and technical variability of the two tests will decrease the number of undiagnosed subjects and will define probability of cystic fibrosis in the undiagnosed group.

Chlorides↗
PubMed1981

Heparin assay and protamine titration.

By utilizing the fact that heparin and protamine sulfate directly neutralize each other, it is possible to quickly detect excess levels of protamine (anti-heparin activity) by back-titrating a plasma specimen with predetermined amounts of heparin. The approach suggested allows for the simultaneous definition of low levels of heparin, and incorporates an equally rapid and accurate measurement of high heparin concentrations. The methodology presented employs heparin assays using the "Protopath" technic. The concept appears to be applicable to other test systems currently designed to monitor heparin activity.

Blood Coagulation Tests↗
PubMed1999

Differential spatial memory impairment after right temporal lobectomy demonstrated using temporal titration.

In this study a temporal titration method to explore the extent to which spatial memory is differentially impaired following right temporal lobectomy was employed. The spatial and non-spatial memory of 19 left and 19 right temporal lobectomy (TL) patients was compared with that of 16 normal controls. The subjects studied an array of 16 toy objects and were subsequently tested for object recall, object recognition and memory for the location of the objects. By systematically varying the retention intervals for each group, it was possible to match all three groups on object recall at sub-ceiling levels. When memory for the position of the objects was assessed at equivalent delays, the right TL group revealed disrupted spatial memory, compared with both left TL and control groups (P < 0.05). MRI was used to quantify the extent of temporal lobe resection in the two groups and a significant correlation between hippocampal removal and both recall of spatial location and object name recall in the right TL group only was shown. These data support the notion of a selective (but not exclusive) spatial memory impairment associated with right temporal lobe damage that is related to the integrity of the hippocampal functioning.

Adult↗
PubMed1985

Immunological titration of 3-N-acetyl-hydroxyamino-4,6-dimethyldipyrido(1,2-a:3',2'-d) imidazole-rat liver DNA adducts.

Antibodies to N-(guanosin-8-yl)-3-N-acetylamino-4,6-dimethyldipyrido(1,2-a :3',2'-d)imidazole were elicited in rabbits by immunization with a conjugate formed between this compound and bovine serum albumin. The specificity of the antibodies was studied by radioimmunoassay. These antibodies were used to titrate the adducts formed in liver DNA of rats treated with 3-N-acetyl-hydroxyamino-4,6-dimethyldipyrido(1,2-a:3',2'-d)imidazo le,p6 a supposed metabolite of the mutagenic amine 3-amino-4,6-dimethyldipyrido(1,2-a:3',2'-d)imidazole (Glu-P-3). It is found that Glu-P-3 residues are covalently bound to the C8 of guanine in acetylated form (70%) and deacetylated form (30%).

Animals↗
PubMed1983

Characterization of the operator sites of the exu regulon in Escherichia coli K-12 by operator-constitutive mutations and repressor titration.

In Escherichia coli, the exu regulon of the hexuronate system involves the three exuT, uxaCA and uxaB operons and is under the negative control of the exuR regulatory gene product. The technique developed by Casadaban, Chou and Cohen was employed to construct two plasmids containing operon fusions in which the lactose genes were fused to the uxaCA and exuT operons. These fusions were transferred into the chromosome by a reciprocal recombination event, and the resulting strains were used for isolation of mutants defective in repression. Two types of operator-constitutive mutants were obtained: one specific for the uxaCA operon expression and the other affecting the exuT gene expression. This genetic evidence confirms that these two operons which are divergently transcribed each possess their own operator site.--The derepressed expression of the two exuT-lac and uxaCA-lac operons and the uxaB gene was also examined upon introduction of plasmids bearing various operators of the exu regulon. The results of testing exuR repressor titration by multiple copies of the exu operators allowed us to show a gradation in the affinity degrees for the three exu operators: uxaBo has the strongest affinity for the exuR repressor and uxaCo the weakest, although that of exuTo seems to be just slightly greater. This gradation may play a role in the control of the exu regulon expression.

Chromosomes, Bacterial↗
PubMed1987

Chequerboard titrations: the influence of the composition of serial dilutions of antibiotics on the fractional inhibitory concentration index and fractional bactericidal concentration index.

Chequerboard titrations carried out with modified serial dilutions of antibiotics such that consecutive concentrations in these series were four times smaller than those in two-fold serial dilutions enable MICs and MBCs to be determined with greater accuracy. Interaction indices calculated by this method can differ markedly from those calculated on the basis of two-fold serial dilutions. The differences calculated in this study ranged from -0.30 to +1.06.

Cefsulodin↗
PubMed1997

Accelerated titration designs for phase I clinical trials in oncology.

BACKGROUND: Many cancer patients in phase I clinical trials are treated at doses of chemotherapeutic agents that are below the biologically active level, thus reducing their chances for therapeutic benefit. Current phase I trials often take a long time to complete and provide little information about interpatient variability or cumulative toxicity. PURPOSE: Our objective was to develop alternative designs for phase I trials so that fewer patients are treated at subtherapeutic dose levels, trials are of reduced duration, and important information (i.e., cumulative toxicity and maximum tolerated dose) needed to plan phase II trials is obtained. METHODS: We fit a stochastic model to data from 20 phase I trials involving the study of nine different drugs. We then simulated new data from the model with the parameters estimated from the actual trials and evaluated the performance of alternative phase I designs on this simulated data. Four designs were evaluated. Design 1 was a conventional design (similar to the commonly used modified Fibonacci method) using cohorts of three to six patients, with 40% dose-step increments and no intrapatient dose escalation. Designs 2 through 4 included only one patient per cohort until one patient experienced dose-limiting toxic effects or two patients experienced grade 2 toxic effects (during their first course of treatment for designs 2 and 3 or during any course of treatment for design 4). Designs 3 and 4 used 100% dose steps during this initial accelerated phase. After the initial accelerated phase, designs 2 through 4 resorted to standard cohorts of three to six patients, with 40% dose-step increments. Designs 2 through 4 used intrapatient dose escalation if the worst toxicity is grade 0-1 in the previous course for that patient. RESULTS: Only three of the actual trials demonstrated cumulative toxic effects of the chemotherapeutic agents in patients. The average number of patients required for a phase I trial was reduced from 39.9 for design 1 to 24.4, 20.7, and 21.2 for designs 2, 3, and 4, respectively. The average number of patients who would be expected to have grade 0-1 toxicity as their worst toxicity over three cycles of treatment is 23.3 for design 1, but only 7.9, 3.9, and 4.8 for designs 2, 3, and 4, respectively. The average number of patients with grade 3 toxicity as their worst toxicity increases from 5.5 for design 1 to 6.2, 6.8, and 6.2 for designs 2, 3, and 4, respectively. The average number of patients with grade 4 toxicity as their worst toxicity increases from 1.9 for design 1 to 3.0, 4.3, and 3.2 for designs 2, 3, and 4, respectively. CONCLUSION: Accelerated titration (i.e., rapid intrapatient drug dose escalation) designs appear to effectively reduce the number of patients who are under-treated, speed the completion of phase I trials, and provide a substantial increase in the information obtained.

Antineoplastic Agents↗
PubMed1989

Absolute mRNA quantification using the polymerase chain reaction (PCR). A novel approach by a PCR aided transcript titration assay (PATTY).

The polymerase chain reaction (PCR) is used as part of a new approach to the absolute quantification of mRNA. We describe a PCR aided transcript titration assay (PATTY) which is based on the co-amplification of an in vitro generated transcript differing by a single base exchange from the target mRNA. Identical portions of a total RNA sample are "spiked" with different amounts of this mutated standard RNA, converted to cDNA and amplified by PCR. Because the base exchange creates a novel restriction endonuclease site, the ratio of co-amplified DNA derived from target mRNA to amplified DNA derived from standard RNA can be determined after restriction endonuclease digestion and separation by gel electrophoresis. This method gives accurate results within 24 hours and is useful especially for the quantification of either low-abundance mRNA or more abundant mRNA present in very small amounts of total RNA. The low-abundance mRNA encoding 4-coumarate:CoA ligase (4CL) in cultured potato cells (Solanum tuberosum L.) was measured in a case study. About 100 molecules per assay could be accurately detected by the new method.

Base Sequence↗
PubMed1977

Polylysine titration of rat liver chromatin fractions after DNase II digestion.

The concentration of free phosphate groups is measured in rat liver chromatin after DNase II digestion using polylysine titration. The unsheared chromatin completely precipitates at lysine/DNA phosphate ratios of 0.5 to 0.6. Digestion of the chromatin reduces the lysine/DNA phosphate ratio of complete precipitation by about 0.2 units suggesting the removal of free phosphate groups. The two chromatin fractions: MgC12 insoluble (template-inactive) and Mg12 soluble (template-active) chromatins precipitate at about the same lysine/DNA phosphate ratio. Some 15% of the MgC12 soluble chromatin remains in solution at any polylysine concentration. The removal of histone H 1 FROM THE MgC12 insoluble chromatin increases the lysine/DNA phosphate ratio by about 0.2 units suggesting that 20% of the DNA phosphate groups in nucleosomes are masked by histone H 1.

Animals↗
PubMed1978

Small-angle X-ray titration of the complex formed between the ribosomal protein S4 and its 16S binding site, S4-RNA: a central core in the 30S subunit.

X-ray scattering titrations at 21 degree C and in ribosomal reconstitution buffer indicate that the S4-RNA and the protein S4 from a 1:1 complex with a stability constant, log K approximately 6.5. When the complex forms, there is only a limited change in the scattering curve indicating that S4-RNA essentially retains its conformation during the complex formation. The increase in the gyration radius as a result of the complex formation, delta R = 4 +/- 3 A, as well as the experimental scattering curve of the complex can be explained by models where the protein S4 is supposed to interact with the periphery of the S4-RNA.

Binding Sites↗