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A neural network based classification scheme for cytotoxicity predictions:Validation on 30,000 compounds.

Elimination of cytotoxic compounds in the early phases of drug discovery can save substantial amounts of research and development costs. An artificial neural network based approach using atomic fragmental descriptors has been developed to categorize compounds according to their in vitro human cytotoxicity. Fragmental descriptors were obtained from the Atomic7 linear logP calculation method implemented in Pallas PrologP program. We used cytotoxicity values obtained from an in-house screening campaign of a diverse set of 30,000 drug-like molecules. The training set included only the most and least toxic 12,998 compounds, however, cytotoxicity data for all compounds were used for validation. The proposed approach can be safely used for filtering out potentially cytotoxic candidates from the development pipeline before synthesis or assays during lead development or lead optimisation. The trained neural network misclassified less than 5% percent of the non-toxic and 9% of the toxic compounds.

Cell Line↗

Adsorption and desorption of phenol on activated carbon and a comparison of isotherm models.

In this study, the potential of activated carbon for phenol adsorption from aqueous solution was studied. Batch kinetics and isotherm studies were carried out to evaluate the effect of contact time, initial concentration, and desorption characteristics of activated carbon. The equilibrium data in aqueous solutions was represented by the isotherm models. Desorption studies to recover the adsorbed phenol from activated carbon performed with NaOH solution. It is necessary to propose a suitable model to gain a better understanding on the mechanism of phenol desorption. For this purpose, pore diffusion and first-order kinetic models were compared. The diffusivity rate (D/r2) and first-order desorption rate (kD) constants were determined as 6.77 x 10(-4) and 3.924 x 10(-4) s(-1), respectively. The two- and three-parameter in the adopted adsorption isotherm models were obtained using a non-linear regression with the help of MATLAB package program. It was determined that best-fitted adsorption isotherm models were determined to be in the order: Langmiur > Toth > Redlich-Peterson > Freundlich isotherms.

Adsorption↗

Relationship of progression of visual field damage to postural changes in intraocular pressure in patients with normal-tension glaucoma.

PURPOSE: To evaluate whether postural changes of intraocular pressure (IOP) are associated with progression of visual field damage in patients with normal-tension glaucoma (NTG). DESIGN: Prospective, noncomparative, nonrandomized study. PARTICIPANTS: Sixty eyes of 33 patients with NTG. METHODS: Intraocular pressure, blood pressure (BP), and pulse rate (PR) were measured in both sitting and supine positions. Visual fields were examined using Humphrey Field Analyzer (HFA; Zeiss-Humphrey Instruments, Inc., San Leandro, CA). Changes in mean deviation (MD) per year (dB/year), that is, MD slope, were calculated by linear regression analysis of the HFA Statpac 2 program. MAIN OUTCOME MEASURES: The relationship between postural changes of IOP and MD slope was analyzed. The correlation between postural changes of IOP and cardiovascular parameters such as BP and PR also was analyzed. RESULTS: The IOP in the supine position was significantly higher than that in the sitting position (P<0.001, paired t test). There was no significant correlation between MD slope and sitting IOP (Pearson r = 0.172; P = 0.188), but a significant correlation was found between MD slope and supine IOP (r = -0.261; P = 0.043). The MD slope significantly correlated with IOP elevation caused by the postural change (r = -0.682; P<0.001). The systolic BP in the supine position correlated with postural changes of IOP (r = 0.364; P = 0.004), but other cardiovascular parameters did not correlate with IOP parameters. CONCLUSIONS: The progression of visual field damage in NTG is associated with IOP in the supine position and the magnitude of IOP elevation accompanying postural changes. These results suggest that deterioration in NTG may occur when patients are lying flat during sleep.

Aged↗

The relationship between static perimetry and the relative afferent pupillary defect.

This study was undertaken to understand better how damage to the anterior visual pathway may affect the relationship between the visual and pupillomotor systems. The relative afferent pupillary defect and the interocular difference in visual field mean deviation (determined by the Humphrey Field Analyzer Statpac program) were correlated in 137 patients. A moderate linear correlation (r = .66) was found. In 25 patients tested by both static and kinetic perimetry, the correlation could not be significantly improved by considering field loss outside of 30 degrees. The correlation was further studied in four subcategories of diagnosis: optic neuritis (n = 36), idiopathic intracranial hypertension (n = 26), compressive optic neuropathy (n = 14), and anterior ischemic optic neuropathy (n = 7). In compressive optic neuropathy and idiopathic intracranial hypertension, the difference in mean deviation between the two eyes was associated with a larger relative afferent pupillary defect than in optic neuritis and anterior ischemic optic neuropathy. In optic neuritis, the correlation was the poorest. These results indicate that diseases of the afferent visual system may not necessarily affect visual threshold (as tested by static perimetry) and the pupillary light reflex (a suprathreshold test) in the same way.

Adolescent↗

Computational models for prediction of IVF/ICSI outcomes with surgically retrieved spermatozoa.

IVF/intracytoplasmic sperm injection (ICSI) using surgically retrieved spermatozoa (SRS) is a key option in the treatment of severe male infertility. It was aimed to develop a computational model for the prediction of this modality's outcome. A dataset of 113 exemplars, derived from patients who underwent IVF/ICSI with SRS, was retrospectively analysed. The dataset, containing input features maternal age, sperm retrieval technique, type of spermatozoa used, type of male factor and output intrauterine pregnancy, was randomized into a modelling ('training') set of 83 and cross-validation ('test') set of 30. neUROn++, a set of C++ programs, was used to model the dataset using linear and quadratic discriminant function analysis, logistic regression, and neural computation. A 4-hidden node neural network was found to have the highest accuracy, with a test set receiver operator characteristic (ROC) curve area of 0.783. Reverse regression of this neural network showed maternal age to be the most significant feature in predicting pregnancy (P = 0.025), followed by sperm type (P = 0.076). Type of male factor (P = 0.47) and sperm retrieval technique (P = 0.88) did not predict outcome. In summary, a neural network of clinical relevance was found to be superior in terms of IVF/ICSI outcome prediction. Future media deployment is planned.

Adult↗

Thermodynamic prediction of polymer retention in temperature-programmed HPLC.

Temperature programming has been used increasingly in liquid chromatography in recent years. In particular, temperature gradient elution has shown great potential in the analysis of complex polymers. In this study, the polymer retention behavior in temperature gradient interaction chromatography is investigated based on thermodynamic consideration of the retention factor. The polymer retention predicted by the model calculation is in good agreement with the experimental results, and the model allows devising a temperature program for designed retention behaviors such as a linear dependence of retention volume on log(molecular weight) of polymers. In addition, the migration behavior of polymeric solute along the separation column can be simulated, which shows strong molecular weight dependence. The migration behavior is also confirmed experimentally by employing different length columns or delayed injection.

Journal Article↗

Assessing program effects in the presence of treatment-baseline interactions: a latent curve approach.

Methods for assessing treatment effects of longitudinal randomized intervention are considered. The focus is on modeling the nonlinear relationship between treatment effects and baseline often observed in prevention programs designed for at-risk populations. Piecewise linear growth modeling was used to study treatment effects during the different periods of development. A multistep multiple-group analysis procedure is proposed for assessing treatment effects in the presence of nonlinear treatment-baseline interactions. Standard errors of the estimates from this multistep procedure were obtained using a bootstrap approach. The methods are illustrated using data from the Johns Hopkins Prevention Research Center involving an intervention aimed at improving classroom behavior.

Humans↗

Twin study of genetic and environmental influences on adult body size, shape, and composition.

OBJECTIVE: To investigate the genetic and environmental influences on adult body size, shape, and composition in women and men, and to assess the impact of age. MATERIALS AND METHODS: In this cross-sectional study of 325 female and 299 male like-sex healthy twin pairs, on average 38 y old (18-67 y), we determined zygosity by DNA similarity, and performed anthropometry and bioelectrical impedance analysis of body composition. The contribution to the total phenotypic variance of genetic, common environment, and individual environment was estimated in multivariate analysis using the FISHER program. Further, these variance components were analysed as linear functions of age. RESULTS: In both women and men genetic contributions were significant for all phenotypes. Heritability for body mass index was 0.58 and 0.63; for body fat%, 0.59 and 0.63; for total skinfolds, 0.61 and 0.65; for extremity skinfolds 0.65 and 0.62; for truncal skinfolds, 0.50 and 0.69; for suprailiac skinfolds, 0.49 and 0.48; for waist circumference, 0.48 and 0.61; for hip, 0.52 and 0.58; for lean body mass/height2, 0.61 and 0.56; and for height, 0.81 and 0.69, respectively. There was no strong evidence of common environmental effects under the assumptions of no nonadditive effect. The pattern of age trends was inconsistent. However, when significant there was a decrease in heritability with advancing age. DISCUSSION: These findings suggest that adult body size, shape, and composition are highly heritable in both women and men, although a decreasing tendency is seen with advancing age.

Adipose Tissue↗

Counting of residual WBCs in WBC-reduced blood components: a multicenter evaluation of a microvolume fluorimeter by the United Kingdom National Blood Service.

BACKGROUND: Implementation of universal WBC reduction of blood components means that automated analytical methods may be the only satisfactory way for production laboratories to meet increased testing requirements. STUDY DESIGN AND METHODS: A multicenter study on the performance of a microvolume fluorimeter (IMAGN 2000, Becton Dickinson) was undertaken on 519 RBC, 353 platelet, and 27 fresh plasma units. RESULTS: WBC counts for the RBC samples ranged from 0.02 to 6.94 x 10(6) per unit (mean, 0.57) as determined by FC and from 0.02 to 5.53 x 10(6) per unit (mean, 0.40) as determined by MVF with a mean FC bias of +0.15 x 10(6) WBCs per unit, and discrepancies outside the 95% limits of agreement were mainly associated with higher FC counts. The series of platelet samples showed means of 0.90 (range, 0.06-19.45) and 0.66 (range, 0.01-18.95) x 10(6) WBCs per unit for FC and MVF methods, respectively. FC and MVF results were in good agreement at low counts, although significant discrepancies were noted at higher counts. Overall, for the platelet units, there was a mean FC bias of +0.34 x 10(6) WBCs per unit. The intermethod agreement exceeded 99 percent for both types of blood component when the single (both UK and United States) decision point of 5.0 x 10(6) WBCs per unit was applied. The mean WBC counts for the 27 analyzed fresh plasma units were 61.8, 56.0, and 46.0 per microL by Nageotte hemocytometry, FC, and MVF, respectively. CONCLUSIONS: This evaluation found that the level of intersite consistency for FC was relatively poor compared to that for MVF. The results nevertheless validated the broad equivalence of FC and MVF results for the current Council of Europe and UK/US decision points of <1.0 and <5.0 x 10(6) WBCs per unit.

Blood Component Removal↗

The contributions of managed care plans to public health practice: evidence from the nation's largest local health departments.

OBJECTIVE: The authors examine the extent and nature of managed care plans participating in local public health activities. METHODS: In 1998, the authors surveyed the directors of all US local health departments serving jurisdictions of at least 100,000 residents to collect information about public health activities performed in their jurisdictions and about organizations participating in the activities. Multivariate logistic and linear regression models were used to examine organizational and market characteristics associated with managed care plan participation in public health activities. RESULTS: Managed care plans were reported to participate in public health activities in 164 (46%) of the jurisdictions surveyed, and to contribute to 13% of the public health activities performed in the average jurisdiction. Plans appeared most likely to participate in public health activities involving the delivery or management of personal health services and the exchange of health-related information. Managed care participation was more likely to occur in jurisdictions with higher HMO penetration, fewer competing plans, and larger proportions of plans enrolling Medicaid recipients. Participation was positively associated with the overall scope and perceived effectiveness of local public health activities. CONCLUSIONS: Although plans participate in a narrow range of activities, these contributions may complement the work of public health agencies.

Administrative Personnel↗

Physician and plan effects on satisfaction of Medicaid managed care patients with their health care and providers.

As many Medicaid patients move into managed care, it is important that physicians competing to serve these patients understand the factors that lead to patient satisfaction. This study uses survey data from 7,313 Oregon Medicaid managed care patients to create a model describing how provider effects and health plan effects relate to patients' satisfaction with their medical care and provider. Path analysis was used to test the explanatory power and strength of relationships in the model. Perceived technical and interpersonal physician quality and health plan rating were most strongly linked with these patients' satisfaction with their care and provider.

Analysis of Variance↗

Assessment of arterial and cardiopulmonary baroreflex gains from simultaneous recordings of spontaneous cardiovascular and respiratory variability.

OBJECTIVES: In usual models of cardiovascular regulation, arterial pressure drives RR interval through a simple baroreflex, and the influence of respiration is dismissed. We examined the applicability of a trivariate autoregressive model to obtain separate values of the gain of the arterial and non-arterial, i.e. cardiopulmonary, components of the lumped baroreflex, employing spontaneous RR interval, systolic arterial pressure and respiration variability. DESIGN: We studied 30 normal subjects (age 37 +/- 1 years), both at rest and during standing, a condition known to enhance sympathetic activity while reducing venous return. Electrocardiogram was obtained by telemetry, arterial pressure by Finapres and respiration with a piezoelectric respiratory belt Data were acquired with a PC and processed with an ad hoc Windows program. METHODS: We employed an additive and a linear multivariate approach to approximate overall gain of the arterial pressure-heart beat period baroreflex (alphalumped) and of its arterial (alphaart) and non-arterial, i.e. cardiopulmonary (alphacp), components, from continuous beat-by-beat series of RR interval, systolic arterial pressure variability and respiration, without using any non-physiological intervention. RESULTS: The overall baroreflex gain at rest (alphalumped = 23.7 +/- 3.4 ms/mmHg) was subdivided into arterial (alphaart = 5.2 +/- 1.0 ms/mmHg) and cardiopulmonary (alphacp = 18.5 +/- 3.2ms/mmHg) components. During active orthostatism, alphaluumped was diminished to 10.0 +/- 2.2 ms/ mmHg. In addition, standing selectively reduced alphacp to 4.8 +/- 1.3 ms/mmHg, while alphaart was not significantly changed. CONCLUSIONS: A trivariate autoregressive model, that considers explicitly the influence of respiration, can subdivide overall, lumped, arterial pressure-heart period baroreflex gain, into two separate components, alphaart and alphacp. Only the latter is reduced by active orthostatism.

Adult↗

A Canadian Indian Health Status Index.

Health care services for registered "band" Indians in Ontario are provided primarily by the Canadian Federal Government. Complex management methods preclude the direct involvement of Indian people in the decisions for their health resource allocation. Health indicators, need, and health status indexes are reviewed. The biostatistics of mortality and demography of the Indian and reference populations are aggregated with hospitalization/morbidity experience as the Chen G'1 Index, as an indicator of normative and comparative need. This is weighted by linear measurements of perceived need for preventive medicine programs, as ranked and scaled values of priorities, Zj. These were determined by community survey on 11 Indian reserves using a non-probabilistic psychometric method of "pair comparisons," based upon "Thurstone's Law of Comparative Judgement.," The calculation of the aggregate single unit Indian Health Status Index [Log.G'1].Zj and its potential application in a "zero-base" budget is described.

Actuarial Analysis↗

National quality monitoring of Medicare health plans: the relationship between enrollees' reports and the quality of clinical care.

BACKGROUND: The clinical quality of health plans varies. The associations between different measures of health plan quality are incompletely understood. OBJECTIVE: To assess the relationships between enrollee reports on the quality of health plans as measured by the Consumer Assessment of Health Plans Study (CAHPS 2.0) survey and the clinical quality of care measured by the Medicare Health Plan Employer Data and Information Set (HEDIS). DESIGN: Observational cohort study. SAMPLE: National sample of 233 Medicare health plans that reported data using the CAHPS 2.0 survey and Medicare HEDIS during 1998. MEASURES: Five composite measures and four ratings derived from the CAHPS survey and six measures of clinical quality from Medicare HEDIS. RESULTS: Two composite measures ("getting needed care" and "health plan information and customer service") were significantly associated with most of the HEDIS clinical quality measures. The proportion of enrollees having a personal doctor was also significantly associated with rates of mammography, eye exams for diabetics, beta-blocker use after myocardial infarction, and follow-up after mental health hospitalization. Enrollees' ratings of health plan care were less consistently associated with HEDIS performance. In multivariable analyses, the measure of health plan communication ("health plan information and customer service") was the most consistent predictor of HEDIS performance. CONCLUSIONS: The pattern of associations we observed among some of the measures suggests that the CAHPS survey and HEDIS are complementary quality monitoring strategies. Our results suggest that health plans that provide better access and customer service also provide better clinical care.

Aged↗

Photosynthetic acclimation is reflected in specific patterns of gene expression in drought-stressed loblolly pine.

Because the product of a single gene can influence many aspects of plant growth and development, it is necessary to understand how gene products act in concert and upon each other to effect adaptive changes to stressful conditions. We conducted experiments to improve our understanding of the responses of loblolly pine (Pinus taeda) to drought stress. Water was withheld from rooted plantlets of to a measured water potential of -1 MPa for mild stress and -1.5 MPa for severe stress. Net photosynthesis was measured for each level of stress. RNA was isolated from needles and used in hybridizations against a microarray consisting of 2173 cDNA clones from five pine expressed sequence tag libraries. Gene expression was estimated using a two-stage mixed linear model. Subsequently, data mining via inductive logic programming identified rules (relationships) among gene expression, treatments, and functional categories. Changes in RNA transcript profiles of loblolly pine due to drought stress were correlated with physiological data reflecting photosynthetic acclimation to mild stress or photosynthetic failure during severe stress. Analysis of transcript profiles indicated that there are distinct patterns of expression related to the two levels of stress. Genes encoding heat shock proteins, late embryogenic-abundant proteins, enzymes from the aromatic acid and flavonoid biosynthetic pathways, and from carbon metabolism showed distinctive responses associated with acclimation. Five genes shown to have different transcript levels in response to either mild or severe stress were chosen for further analysis using real-time polymerase chain reaction. The real-time polymerase chain reaction results were in good agreement with those obtained on microarrays.

Acclimatization↗

Diverse optical characteristic of the prostate and light delivery system: implications for computer modelling of prostatic photodynamic therapy.

OBJECTIVE: To explore the use of photodynamic therapy (PDT) as a minimally invasive form of treatment for organ-confined prostate cancer, for although there are several therapies, ablative treatments are associated with significant morbidity. MATERIALS AND METHODS: Using the photosensitizer tin etiopurpurin, dogs were treated with interstitially placed laser fibres in an effort to validate PDT for treating prostate cancer. Earlier models assumed a uniform distribution of light output from a cylindrical fibre and a uniform attenuation coefficient throughout the prostate. Subsequent observations show that this model was too simple and that light radiance is not linear. To overcome under-treatment, a computer program to complement real-time fibre placement was developed. RESULTS: As light radiance from interstitially placed laser fibres varies significantly from the commonly assumed ideal cylindrical emission, a predictive mathematical model of prostate PDT needs to consider the real emission. Also, the optical properties of the prostate, e.g. absorption and scattering of light, are anisotropic. Differences in the attenuation coefficient (combining absorption and scattering of light) also varied among different animals. Incorporating all these variables into a computer program produced a virtual model of the photo-ablated zone within +/- 2 mm of that observed in animals. CONCLUSION: PDT of the prostate is not trivial and should benefit from computer-aided methods as it is developed for clinical use.

Animals↗