Relevance of the 10X Uncertainty Factor to the Risk Assessment of Drugs Used by Children and Geriatrics

Conventional risk assessment practices utilize a tenfold uncertainty factor (UF) to extrapolate from the general human population to sensitive subgroups, such as children and geriatrics. This study evaluated whether the tenfold UF can be reduced when pharmacokinetic and pharmacodynamic data for pharmaceuticals used by children and geriatrics are incorporated into the risk assessment for human sensitivity. Composite factors (kinetics X dynamics) were calculated from data-derived values for bumetanide, furosemide, metoprolol, atenolol, naproxen, and ibuprofen. For the compounds examined, all of the composite factors were lower than 10. Furthermore, 8 of the 12 composite factors were less than 5.5. Incorporation of human kinetic and dynamic data into risk assessment can aid in reducing the uncertainties associated with sensitive subgroups and further study is encouraged.     

A Study of Safety Factors for Risk Assessment of Drugs Used for Treatment of Attention Deficiency Hyperactivity Disorder in Sensitive Populations

The aim of this study was to search the literature through the library and Internet resources from pharmaceutical companies and associations to obtain pharmacoki-netic and pharmacodynamic data for six of the most used drugs for treatment of Attention Deficiency Hyperactivity Disorder (ADHD). The drugs included meth-ylphenidate, pemoline, haloperidol, bupropion, imipramine, and desipramine. The data collected allowed the evaluation of the 10X uncertainty factor, which was related to healthy adults and sensitive populations (children, elderly and health affected). Once the extensive database review was completed, the data were used to calculate a composite factor (kinetics x dynamics) for each drug. Ten of the 12 data-derived composite factors were less than 10. Therefore, incorporation of human kinetic and dynamic data into risk assessment can help to reduce the uncertainties associated with sensitive subgroups.     

Application of Kinetic and Dynamic Data for Antihistamines to Risk Characterization in Sensitive Populations

A major goal of risk assessment is to protect the health of individuals who may be more sensitive than the general population. This study compared human phar-macokinetic and pharmacodynamic data in sensitive groups (i.e., children, the elderly, diseased states, and poor metabolizers) versus young, healthy adults for the antihistamines cetirizine, fexofenadine, loratadine, azelastine, ebastine, chlorpheniramine, and diphenhydramine. The default components (3.16 each for kinetic and dynamic aspects) of the intraspecies uncertainty factor were adjusted with compound specific data for the antihistamines. The majority (16 of 18) of the composite factors (kinetics X dynamics) for the sensitive groups were less than 10. Children had the lowest composite factors for antihistamines, ranging from 1.1 to 6.3. Application of kinetic and dynamic data for antihistamines to the Renwick/International Programme on Chemical Safety (IPCS) scheme can aid in characterizing the extent of variability in sensitive populations, thereby reducing the uncertainty associated with the risk assessment of sensitive populations.     

Intra-Species Extrapolation in Risk Assessment of Different Classes of Antimicrobials

The risk assessment process for non-carcinogens incorporates all available scientific information, including toxicokinetic and toxicodynamic data. A 10-fold uncertainty factor (UF) is most commonly used to account for underlying variability within the human species. The purposes of this investigation are to evaluate whether the magnitude of the 10X-UF can be reduced when pharmacokinetic and pharma-codynamic data are incorporated to characterize interindividual variability and whether another UF is needed for the children group. An extensive literature search was conducted on seven antimicrobials in order to incorporate information on kinetics and dynamics to allow extrapolation among susceptible humans. The drugs are cefaclor, cefuroxime, erythromycin, clarithromycin, ampicillin, gentamicin and amikacin. The composite factor was calculated using the highest ratio for appropriate parameters and default subfactor. According to the data, we concluded that when relevant kinetic and dynamic data are available, replacing the default factors with actual data-derived values was possible for the antimicrobials evaluated and that there is no need to add another UF to the children group.     

The Use of Kinetic and Dynamic Data in Risk Assessment of Drugs

The risk assessment process for non-carcinogens must incorporate all available scientific information, including toxicokinetic and toxicodynamic data. The framework for exposure limit setting proposed by Renwick and the International Programme on Chemical Safety (IPCS) subdivides traditional 10X uncertainty factors (UFs) into separate partial-log default values based on kinetic and dynamic considerations and allows for incorporation of compound-specific data when available. In this investigation, an extensive literature search was conducted on nine pharmaceuticals in order to incorporate information on kinetics and dynamics to allow extrapolation across species and among susceptible humans. The drugs are diazepam, oxazepam, midazolam, buspirone, fluoxetine, venlafaxine, amlodipine, felodipine, and nifedipine. The composite factors were calculated using the highest ratio or the average ratio for appropriate parameters and default subfactor. For the drugs examined, most of the subfactors for kinetics and dynamics were less than the proposed values by Renwick and IPCS, and the composite factors were far less than 100. From this study, it was concluded that relevant compound-specific kinetic and dynamic data can reduce uncertainties associated with interspecies differences and interindividual variability.     

Inter- and Intra-Species Extrapolation in Risk Assessment of Different Classes of Pesticides

Risk assessors routinely use the reference dose (RfD) approach for non-cancer risk assessment. In this approach, No-Observed-Adverse-Effect-Level (NOAEL) is divided by the product of uncertainty factors (UFs) and, occasionally, an additional modifying factor (MF), each usually employed by default as factors of 10. In the present investigation, kinetic and dynamic data have been used in order to reduce uncertainties when establishing exposure guidelines for examples of chemicals representing four classes of pesticides (warfarin, lindane, carbaryl and parathion). An intensive search of databases was conducted for these pesticides, and toxicokinetic and toxicodynamic parameters in inter- and intra-species were evaluated. The kinetic and dynamic subfactors were less than the proposed values of Renwick and the International Programme on Chemical Safety (IPCS). The composite factors for all the examined pesticides were less than 100. The present study indicated that in setting exposure levels it is important to incorporate kinetic and dynamic data, as they become available, rather than rely on default uncertainty factors, which are imprecise in many cases.     

Gait asymmetry: composite scores for mechanical analyses of sprint running

Gait asymmetry analyses are beneficial from clinical, coaching and technology perspectives. Quantifying overall athlete asymmetry would be useful in allowing comparisons between participants, or between asymmetry and other factors, such as sprint running performance. The aim of this study was to develop composite kinematic and kinetic asymmetry scores to quantify athlete asymmetry during maximal speed sprint running. Eight male sprint trained athletes (age 22±5 years, mass 74.0±8.7 kg and stature 1.79±0.07 m) participated in this study. Synchronised sagittal plane kinematic and kinetic data were collected via a CODA motion analysis system, synchronised to two Kistler force plates. Bilateral, lower limb data were collected during the maximal velocity phase of sprint running (velocity=9.05±0.37 ms(-1)). Kinematic and kinetic composite asymmetry scores were developed using the previously established symmetry angle for discrete variables associated with successful sprint performance and comparisons of continuous joint power data. Unlike previous studies quantifying gait asymmetry, the scores incorporated intra-limb variability by excluding variables from the composite scores that did not display significantly larger (p<0.05) asymmetry than intra-limb variability. The variables that contributed to the composite scores and the magnitude of asymmetry observed for each measure varied on an individual participant basis. The new composite scores indicated the inter-participant differences that exist in asymmetry during sprint running and may serve to allow comparisons between overall athlete asymmetry with other important factors such as performance.     

Human metapneumovirus

Human metapneumovirus (hMPV), first isolated in the Netherlands in 2001, is a member of the genus Metapneumovirus of the sub-family Pneumovirinae of the family Paramyxoviridae. The genomic organization of hMPV is 3'-N-P-M-F-M2-SH-G-L-5'. hMPV resembles the sole member of this genus, avian pneumovirus. hMPV is the most closely related human pathogen to respiratory syncytial virus. Phylogenetic analysis of the nucleotide sequences indicated that there were two genetic groups. Furthermore, each group could be subdivided into two subgroups. hMPV encodes three surface proteins, F, G and SH proteins. The majority of antibodies to hMPV in serum were antibody against F protein, which mediates cross-group neutralization and protection. The incidences of hMPV-associated respiratory infection estimate 5 to 10% in children and 2 to 4% in adults. hMPV generally causes upper respiratory tract infection and flu-like illness, the virus can be associated with lower tract infections, such as wheezy bronchitis, bronchitis, bronchiolitis and pneumonia, in very young children, elderly persons, and immunocompromised patients. hMPV has a seasonal peak during the spring in Japan. Reinfection with hMPV frequently occurs in children, implying that the host immune response induced by natural infection provides incomplete protection. The RT-PCR test is the most sensitive test for detection of hMPV.     

Development of an electrochemical immunosensor for alanine aminotransferase

Alanine aminotransferase (ALT) has been regarded as one of the most sensitive indicators of hepatocellular damage. While ALT is widely used in the practice of medicine, few attempts have been made to develop biosensors applicable to the on-site diagnosis of liver diseases. In the hope of developing an immunosensor for measurement of ALT activity, we have generated monoclonal antibodies to human recombinant ALT and fabricated them for use in a sensor. The ALT immunosensor was composed of the followings: (1) anti-ALT antibody-immobilized outer membrane; (2) pyruvate oxidase-absorbed inner membrane; (3) a self assembled monolayer mediator-coated gold working electrode and an Ag/AgCl reference electrode. The chronoamperometric measurement of the immunosensor was performed with 40 microl of PBS containing substrates and ALT without a washing step in less than 5 min. The dynamic range of ALT immunosensor was presented as five orders of magnitude, ranging between 10 pg/ml and 1 microg/ml. The detection limit and the sensitivity were 10 pg/ml and 26.3 nA/(ng/ml), respectively. In the meantime, the enzyme sensor fabricated without anti-ALT antibody showed much poorer analytical values. The dynamic range, the detection limit, and the sensitivity were 10 ng/ml-100 microg/ml, 10 ng/ml and 11.4 nA/(ng/ml), respectively. The presented results indicated that the immunosensor system provided much better technical performance in all of the aspects evaluated than did the enzyme sensor without the immobilized-antibody.     

Induction of 7-ethoxycoumarin o-deethylase activity in cultured human epithelial cells by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD): evidence for TCDD receptor

The responsiveness of 5 human squamous cell carcinoma (SCC) lines derived from tumors of the epidermis and tongue to 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) was assessed by measuring the induction of the cytochrome P1-450-mediated monooxygenase activity, 7-ethoxycoumarin O-deethylase (ECOD). In 4 of the SCC lines the EC50 for this response was approximately 10(-9)M, whereas in one line the EC50 was 10(-10)M. In each of the less sensitive lines a concentration of 10(-10)M TCDD elicited less than 5% of the maximal enzyme activity. Specific binding of radiolabeled TCDD was detected in the cytosol fraction from all the SCC lines. The relative amount of receptor measured in each line correlated with maximally-induced ECOD activity. The data indicate that human cell lines derived from a target tissue for TCDD toxicity contain the TCDD receptor and show differential sensitivity to TCDD analogous to the murine strain differences in sensitivity regulated by the Ah locus.     

Gall-bladder sensitivity to cholecystokinin in patients with gall stones.

Gall-bladder sensitivity to cholecystokinin (CCK) was determined by dynamic cholescintigraphy in 18 patients with radiolucent gall stones and 18 matched controls during an infusion of CCK in which the rate of infusion was increased. In 10 of the matched pairs the patient was more sensitive than the control, in one the control was more sensitive, and in seven no difference was detected (p = 0.012). It is concluded that patients with cholesterol gall stones have increased gall-bladder sensitivity to CCK, and that this may be important in the pathogenesis of this disease.     

Usefulness and limitation of measurement of insulin-like growth factor binding protein-3 (IGFBP-3) for diagnosis of growth hormone deficiency.

To analyze the utility of insulin-like growth factor binding protein-3 (IGFBP-3) radioimmunoassay for diagnosis of growth hormone deficiency (GHD) we measured IGFBP-3 in sera from normal children, short children and patients with GHD. The sensitivity (true positive ratio) of IGFBP-3 for complete GHD (cGHD) was 93%, while the specificity (true negative ratio) for normal short children (NS) was 88%. In contrast, the sensitivity of IGFBP-3 for partial GHD (pGHD) was only 43%. The poor discrimination between patients with pGHD and NS may be the result of their relatively similar GH level, as compared to cGHD, or due to the limitations of GH stimulation tests. The specificity of IGFBP-3 for NS was excellent in children of all ages: less than 10 years old (87%) and older than 10 (88%). However, sensitivity for GHD was good for children less than 10 years old (84%) but poor for children older than 10 (64%). IGFBP-3 may be less sensitive for diagnosing GHD in older children because IGFBP-3 levels may also increase during puberty due to mechanisms independent of the GH-IGF-I axis.     

Those ubiquitous fertility trends: United States, 1945-1979

1970-79 US fertility trends among differnet racial, regional, age, educational, parity, and socioeconomic subgroups in the population were examined, using own children data from the 1976 Survey of Income and Education (SIE) and the March Current Population Surveys (CPS) from 1968-80. In addition, cross-sectional differences in fertility for the subgroups were compared for 1970 and 1976, using multiple regression analysis. 1st, the appropriateness of using fertility rates obtained from own children data was assessed by comparing fertility rates obtained from the SIE data with those derived from vital statistic and census data. The comparative analysis confirmed that the SIE data yielded an accurate estimate of period fertility rates for currently married women, provided the subgroup samples were sufficiently large. CPS fertility estimates were also judged to be accurate if data from 3 adjacent survey years was pooled to increase sample size. Fertility trends for 5 educational groups were assessed separately for 1967-73. During this periold, there was a marked decline in fertility for all 5 groups; for the group with 5-8 years of education the decline was only 14%, but for the other 4 groups, which included women with 9-16 or more years of education, the decline in fertility ranged from 26-29%. In assessing the 1970-76 trends, the sample was restricted to own children, aged 3 years or less, of currently married women, under 40 years of age. Among whites, there was an overall 20% decline in fertility between 1970-76 and an overall fertility increase of about 2% between 1976-79. These trends were observed in all 28 white subgroups. A similar pattern was observed for blacks. There was an overall fertility decline of 24% between 1970-76, and this decline was apparent for all subgroups except women with college degrees. Betwen 1976-79, black fertility rates, unlike white rates, continued to decline, but the rate of decline was only 3%. Furthermore, the decline in almost all the black subgroups was markedly less than in the 1970-76 periold, and for many of the subgroups the trend was reversed and fertility increased. In summary, the fertility trends noted for 1970-79 were pervasive for almost all the subgroups for both blacks and whites; i.e., there was a marked decline in fertility between 1970-76 and than a reversal or slowing down of the decline during the 1976-79 for all black and white subgroups. Cross-sectional fertility differences in the subgroups in 1970 and in 1979 were quite similar, and fertility rates differed markedly for the separate subgroups. These differences do not, of course, explain the pervasive trends observed in the analysis of the fertility rates over time. A similar study assessing fertility trends among subgroups for the early 1940's through the late 1960s also revealed the pervasive nature of period fertility trends. Demographers have not as yet been able to explain these shifts in fertility that cut across all subgroups in the US and which also characterize the period fertility rates in other developed countries. Tables provided information on 1) total fertility rates by educational level and by geographical region for 1945-1975; 2) % change in number of own children less than 3 years of age among women under age 40 by maternal age, maternal education, initial parity, geographical region, and husband's income; and 3) mean number of own children less than 3 years of age among women under age 40 by maternal age, education, parity, region, and husband's income.     

Detection of postvaccination mumps virus antibody by neutralization test, enzyme-linked immunosorbent assay and sensitive hemagglutination inhibition test

A group of 251 children aged 2-3 years given live attenuated mumps virus vaccine PAVIVAC of Czechoslovak production were tested for antiparotitis antibody levels in pre- and postvaccination sera by neutralization test (NT), enzyme-linked immunosorbent assay (ELISA) and sensitive hemagglutination inhibition test, enhanced by heterologous antibody to human immunoglobulin G (E-HIT). The prevaccination findings were as follows: positive ELISA IgG titres, neutralization antibodies and hemagglutination inhibition antibodies were present in, respectively, 35%, 25.9% and 27.9% of the sera. Postvaccination seroconversions were evaluated in 159 susceptible vaccinees whose prevaccination sera had been negative by all three tests. The lowest seroconversion was detected by NT (74.2%), seroconversions by ELISA and E-HIT were appreciably higher (82.4% and 86.8%, respectively). The seven children showing a seroconversion by E-HIT but not by ELISA had a 4 fold increase of anti-mumps ELISA IgG antibodies as well, but the rise of antibody titres was at a level falling in the range below the positivity criterion for ELISA. The statistically evaluated detection rate for antibodies was significantly higher (significance test "t") by ELISA as compared with neutralization test. However, antibody levels (geometric mean titres) were 8-10 times lower in postvaccination sera than in convalescent sera of 30 children with mumps in all three tests.     

A new high resolution screening method for study of phenotype stress responses of Saccharomyces cerevisae mutants

A high resolution high throughput screening method has been developed for stress response phenotyping of the global Saccharomyces cerevisiae knock out mutant collection. Stress causing agent is added at three concentrations to individual mutant cultures growing in early exponentially phase in 384-well microplates, and the dynamic effect of stress agent exposure is measured by following subsequent growth profiles of individual mutants with a resolution of three optical density measurements per hour. Software was written for calculation of sensitivity coefficients and efficient visual inspection of the growth and inhibition curves. Three DNA damage response causing agents were chosen to explore the feasibility of the new screening method: methyl methanesulphonate, 5-fluorouracil and cisplatin. They were tested in three biological replicas on a 1400 mutant large sub-library of the homozygote diploid S. cerevisiae gene knock out collection. The sub-library consisted of only mutants with a human ortholog to the inactivated gene. Almost 400 mutants were found more sensitive to one or more of the agents. Forty-nine mutants were sensitive to all three agents. One of the mutants, ERK5, sensitive to all three agents was chosen for follow-up human cell experiments to verify that such yeast screens can be used as hypothesis generator for human cell studies. Similar to yeast, HeLa cells became more sensitive against all three DNA damaging agents when co-treated with the ERK5 inhibitor BIX21088, thus supporting the result from the yeast phenotype screen.     

Specifying social structures in preschool classrooms: descriptive and functional distinctions between affiliative subgroups

Preschool children attending Head Start programs (N = 586, 296 boys and 290 girls, between 3 and 5 years of age, over 95% African–American) were observed to determine physical proximity to peers as well as rates of visual attention given and received. Sociometric data were used to derive peer acceptance scores, peer friendships, and sociometric status classifications. Three subgroup types (high mutual proximity (HMP), lower mutual proximity (LMP), and ungrouped children) were identified through complete linkage hierarchical clustering and chi-square procedures from the proximity data. HMP subgroups tended to be larger, to have higher sociometric acceptance scores, and children in these subgroups had more reciprocated friendships than was true for the other subgroup types. Significant within-group preferences and out-group biases were observed for both HMP and LMP subgroups using measures of visual attention and sociometric choice data, but these were more marked for HMP subgroups. Results are consistent with previous ethological studies of affiliative structures in preschool classrooms and also show that methods of data collection and analysis from social ethology and child psychology research traditions are mutually informing.     

A new high resolution screening method for study of phenotype stress responses of Saccharomyces cerevisae mutants

A high resolution high throughput screening method has been developed for stress response phenotyping of the global Saccharomyces cerevisiae knock out mutant collection. Stress causing agent is added at three concentrations to individual mutant cultures growing in early exponentially phase in 384-well microplates, and the dynamic effect of stress agent exposure is measured by following subsequent growth profiles of individual mutants with a resolution of three optical density measurements per hour. Software was written for calculation of sensitivity coefficients and efficient visual inspection of the growth and inhibition curves. Three DNA damage response causing agents were chosen to explore the feasibility of the new screening method: methyl methanesulphonate, 5-fluorouracil and cisplatin. They were tested in three biological replicas on a 1400 mutant large sub-library of the homozygote diploid S. cerevisiae gene knock out collection. The sub-library consisted of only mutants with a human ortholog to the inactivated gene. Almost 400 mutants were found more sensitive to one or more of the agents. Forty-nine mutants were sensitive to all three agents. One of the mutants, ERK5, sensitive to all three agents was chosen for follow-up human cell experiments to verify that such yeast screens can be used as hypothesis generator for human cell studies. Similar to yeast, HeLa cells became more sensitive against all three DNA damaging agents when co-treated with the ERK5 inhibitor BIX21088, thus supporting the result from the yeast phenotype screen.     

In-tube solid-phase microextraction coupled to liquid chromatography (in-tube SPME/LC) analysis of nontricyclic antidepressants in human plasma

A sensitive, selective, and reproducible in-tube solid-phase microextraction and liquid chromatographic (in-tube SPME/LC-UV) method for simultaneous determination of mirtazapine, citalopram, paroxetine, duloxetine, fluoxetine, and sertraline in human plasma was developed, validated and further applied to the analysis of plasma samples from elderly patients undergoing therapy with antidepressants. Important factors in the optimization of in-tube SPME efficiency are discussed, including the sample draw/eject volume, draw/eject cycle number, draw/eject flow-rate, sample pH, and influence of plasma proteins. The quantification limits of the in-tube SPME/LC method varied between 20 and 50ng/mL, with a coefficient of variation lower than 10%. The response of the in-tube SPME/LC method for most of the drugs was linear over a dynamic range from 50 to 500ng/mL, with correlation coefficients higher than 0.9985. The in-tube SPME/LC can be successfully used to analyze plasma samples from ageing patients undergoing therapy with nontricyclic antidepressants.     

A Composite Model for Subgroup Identification and Prediction via Bicluster Analysis

Background

A major challenges in the analysis of large and complex biomedical data is to develop an approach for 1) identifying distinct subgroups in the sampled populations, 2) characterizing their relationships among subgroups, and 3) developing a prediction model to classify subgroup memberships of new samples by finding a set of predictors. Each subgroup can represent different pathogen serotypes of microorganisms, different tumor subtypes in cancer patients, or different genetic makeups of patients related to treatment response.

Methods

This paper proposes a composite model for subgroup identification and prediction using biclusters. A biclustering technique is first used to identify a set of biclusters from the sampled data. For each bicluster, a subgroup-specific binary classifier is built to determine if a particular sample is either inside or outside the bicluster. A composite model, which consists of all binary classifiers, is constructed to classify samples into several disjoint subgroups. The proposed composite model neither depends on any specific biclustering algorithm or patterns of biclusters, nor on any classification algorithms.

Results

The composite model was shown to have an overall accuracy of 97.4% for a synthetic dataset consisting of four subgroups. The model was applied to two datasets where the sample’s subgroup memberships were known. The procedure showed 83.7% accuracy in discriminating lung cancer adenocarcinoma and squamous carcinoma subtypes, and was able to identify 5 serotypes and several subtypes with about 94% accuracy in a pathogen dataset.

Conclusion

The composite model presents a novel approach to developing a biclustering-based classification model from unlabeled sampled data. The proposed approach combines unsupervised biclustering and supervised classification techniques to classify samples into disjoint subgroups based on their associated attributes, such as genotypic factors, phenotypic outcomes, efficacy/safety measures, or responses to treatments. The procedure is useful for identification of unknown species or new biomarkers for targeted therapy.