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At least 595 records · Page 33Linked to original sources
PubMed2005

Autocorrelation of molecular electrostatic potential surface properties combined with partial least squares analysis as new strategy for the prediction of the activity of human A(3) adenosine receptor antagonists.

The combination of molecular electrostatic potential (MEP) surface properties (autocorrelation vectors) with the conventional partial least squares (PLS) analysis has been used for the prediction of the human A(3) receptor antagonist activities. Three-hundred-fifty-eight structurally diverse human A(3) receptor antagonists have been utilized to generate a novel ligand-based three-dimensional structure-activity relationship. Remarkably, our chemical library includes all 21 important chemical classes of human A(3) antagonists currently discovered, and it represents the largest molecular collection used to generate a general human A(3) antagonist structure-activity relationship. A robust quantitative model has been obtained as described by both cross-validated correlation coefficient (r(cv) = 0.81) and prediction capability (r(pred) = 0.82). The proposed MEP/PLS approach can be considered as an alternative hit identification tool in virtual screening applications.

Adenosine A3 Receptor Antagonists↗
PubMed1999

A unified and quantitative receptor model for the microtubule binding of paclitaxel and epothilone.

[formula: see text] Paclitaxel and epothilone represent the two major classes of antimicrotubule agents that promote tubulin polymerization and, presumably, mitotic arrest during cell division. A common minireceptor binding site model at beta-tubulin has been constructed for these structurally divergent compounds. Utilizing 20 amino acids identified in photoaffinity labeling experiments, the 3-D model correlates measured and predicted Ki's with r = 0.99 and rms(delta Gcalc-delta Gexp) = 0.2 kcal/mol. In addition, the model predicts the affinity of compounds not used in the training set and explains much of the SAR for the paclitaxel and epothilone families.

Antineoplastic Agents↗
PubMed2000

Overview of CARMEM: a new dynamic quantitative cardiac model for ECG monitoring and its adaptation to observed signals.

Different approaches have been proposed in order to achieve knowledge integration for coronary care monitoring applications, usually in the form of expert systems. The clinical impact of these expert systems, which are based only on "shallow" knowledge, has not been remarkable due to the difficulties associated with the construction and maintenance of a complete knowledge base. Model-based systems represent an alternative to these problems because they allow efficient integration of the "deep" knowledge on the underlying physiological phenomena being monitored. In this work, a brief review of existing model-based systems for cardiac rhythm interpretation is presented, followed by the description of a new system for Cardiac Arrhythmia Recognition by Model-Based ECG Matching (CARMEM). Fundamental characteristics of CARMEM are presented; in particular, its ability to provide online parameter adaptation to simulate complex rhythms and to match observed ECG signals. The proposed model can be useful for the explanation of the origin of cardiac arrhythmias and contribute towards their robust characterization in the context of coronary care units.

Artificial Intelligence↗
PubMed2005

Rethinking the mood and anxiety disorders: a quantitative hierarchical model for DSM-V.

The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994) groups disorders into diagnostic classes on the basis of the subjective criterion of "shared phenomenological features." There are now sufficient data to eliminate this rational system and replace it with an empirically based structure that reflects the actual similarities among disorders. The existing structural evidence establishes that the mood and anxiety disorders should be collapsed together into an overarching class of emotional disorders, which can be decomposed into 3 subclasses: the bipolar disorders (bipolar I, bipolar II, cyclothymia), the distress disorders (major depression, dysthymic disorder, generalized anxiety disorder, posttraumatic stress disorder), and the fear disorders (panic disorder, agoraphobia, social phobia, specific phobia). The optimal placement of other syndromes (e.g., obsessive-compulsive disorder) needs to be clarified in future research.

Anxiety Disorders↗
PubMed2004

A quantitative model-based approach to examining aging effects on information-integration category learning.

Information-integration category learning was examined in older and younger adults. Accuracy results indicated that older participants learned less well than younger participants in both linear and nonlinear conditions. Model-based analyses indicated that both groups in the linear condition tended to use information integration but that later in training younger participants were more likely to do so. In contrast, the 2 groups in the nonlinear condition were equally likely to use information integration. Further analysis indicated that younger adults were more accurate than older adults when an information-integration approach was adopted, whereas fewer age-related differences were observed when a rule-based approach was used, suggesting that age can have a negative impact on information-integration category learning processes but less impact on rule-based learning.

Adult↗
PubMed1998

Efficacy of orchidopexy on spermatogenesis in the immature mutant 'trans-scrotal' rat as a cryptorchid model by quantitative cytological analysis.

OBJECTIVES: To determine whether cryptorchidism is a congenital malformation and whether the impaired spermatogenesis in immature testes can be reversed by early orchidopexy, using the mutant trans-scrotal (T-S) rat which is normally masculinized but has cryptorchidism in 85% of males. MATERIALS AND METHODS: First, T-S rats (six per group) with ectopic testes destined to be undescended were investigated histologically at 4, 7 and 14 days after birth. Secondly, 12-day-old T-S rats were divided into four groups which underwent different procedures, i.e. 1, with normally descending testes (normal control, 10 rats); 2, with undescended testes (UDT) treated by orchidopexy (treated UDT, eight rats); 3, with UDT treated by a sham operation (sham-operated UDT, six rats); and 4, with UDT left untreated (untreated UDT, six rats). Thirty days after operation the testicular anatomy was recorded; excised testes were examined histologically and different types of germ cells were counted per tubule cross-section microscopically. RESULTS: There were no quantitative or morphological differences in the numbers of gonocytes, type-A spermatogonia or Leydig cells in the seminiferous tubules between normal and ectopic testes in the first 14 days after birth. However, by 21 days of age spermatogenesis in the UDT had declined with transformation from primary leptotene spermatocytes to spermatids. There were significantly more Leydig cells in the untreated UDT at 30 days than in normal control testes. The impaired spermatogenesis in UDT was restored by early orchidopexy and there were significantly more seminiferous tubules at stage 3 (pachytene spermatocytes) and stage 4 (spermatids) than in the untreated or sham-operated groups (P < 0.001). CONCLUSIONS: These results show that in the T-S rat with cryptorchidism, the testicular damage is not a congenital malformation and can be reversed with early surgical correction.

Animals↗
PubMed2000

Tachycardia: an autosomal, monogenic, biallelic, recessive trait.

A brief commentary of the genetics of blood pressure is presented. The importance of the mechanisms of blood pressure regulation, among which heart rate is relevant, is emphasized. The analysis of a small population to test the quantitative model of the trait heart rate, considered as a metric character, is presented. The analysis of heart rate fitting to a qualitative model of inheritance is carried out. The results displayed might support the hypothesis that tachycardia could be an autosomal, monogenic, biallelic recessive trait.

Alleles↗
PubMed1983

A quantitative genetic model of reciprocal altruism: a condition for kin or group selection to prevail.

A condition is derived for reciprocal altruism to evolve by kin or group selection. It is assumed that many additively acting genes of small effect and the environment determine the probability that an individual is a reciprocal altruist, as opposed to being unconditionally selfish. The particular form of reciprocal altruism considered is TIT FOR TAT, a strategy that involves being altruistic on the first encounter with another individual and doing whatever the other did on the previous encounter in subsequent encounters with the same individual. Encounters are restricted to individuals of the same generation belonging to the same kin or breeding group, but first encounters occur at random within that group. The number of individuals with which an individual interacts is assumed to be the same within any kin or breeding group. There are 1 + i expected encounters between two interacting individuals. On any encounter, it is assumed that an individual who behaves altruistically suffers a cost in personal fitness proportional to c while improving his partner's fitness by the same proportion of b. Then, the condition for kin or group selection to prevail is [Formula: see text] if group size is sufficiently large and the group mean and the within-group genotypic variance of the trait value (i.e., the probability of being a TIT-FOR-TAT strategist) are uncorrelated. Here, C, Vb, and Tb are the population mean, between-group variance, and between-group third central moment of the trait value and r is the correlation between the additive genotypic values of interacting kin or of individuals within the same breeding group. The right-hand side of the above inequality is monotone decreasing in C if we hold Tb/Vb constant, and kin and group selection become superfluous beyond a certain threshold value of C. The effect of finite group size is also considered in a kin-selection model.

Altruism↗
PubMed2001

Quantitative genetic modeling of variation in human brain morphology.

The degree to which individual variation in brain structure in humans is genetically or environmentally determined is as yet not well understood. We studied the brains of 54 monozygotic (33 male, 21 female) and 58 dizygotic (17 male, 20 female, 21 opposite sex) pairs of twins and 34 of their full siblings (19 male, 15 female) by means of high resolution magnetic resonance imaging scans. Structural equation modeling was used to quantify the genetic and environmental contributions to phenotypic (co)variance in whole brain, gray and white matter volume of the cerebrum, lateral ventricle volume and associated variables such as intracranial volume and height. Because the cerebral cortex makes up more that two-thirds of the brain mass and almost three-quarters of its synapses, our data predominantly concerns the telencephalon. Genetic factors accounted for most of the individual differences in whole brain (90%), gray (82%) and white (88%) matter volume. Individual differences in lateral ventricle volume were best explained by a model containing common (58%) and unique (42%) environmental factors, indicating genes to be of no or minor influence. In our sample, genetic or environmental influences were not different for males and females. The same genes influenced brain volumes and intracranial volume and almost completely explained their high phenotypic correlation. Genes influencing gray and white matter overlapped to a large extent and completely determined their phenotypic correlation. The high heritability estimates that were found indicate that brain volumes may be useful as intermediate phenotypes in behavioral genetic research.

Adult↗
PubMed2000

Primary placement of a titanium motility post in a porous polyethylene orbital implant: animal model with quantitative assessment of fibrovascular ingrowth and vascular density.

PURPOSE: To determine whether a Medpor porous polyethylene orbital implant, at the time of initial orbital implant surgery, will tolerate the insertion of a titanium screw on the anterior surface of the implant. METHODS: Twelve New Zealand white rabbits were enucleated and implanted with a porous polyethylene orbital implant. At the time of enucleation, the porous polyethylene orbital implants were drilled, and titanium motility coupling posts were inserted. The motility coupling posts were inserted at two projection heights (2 or 4 mm) and either covered within Tenon capsule/conjunctiva (eight implants) or left exposed (four implants). Rabbits were killed at 6 or 12 weeks. Clinical tissue tolerance, histologic response to the motility coupling post, and vascular density of the porous polyethylene orbital implant were evaluated. RESULTS: The motility coupling posts were well tolerated, and extrusion or migration of the motility coupling post did not occur. The average percentage cross-sectional area of the implant occupied by fibrovascular tissue at 6 and 12 weeks was 76.3% and 97.5%, respectively. In comparing the vascular density (number of vessels per square millimeter) in the porous polyethylene orbital implant within a 1-mm zone immediately surrounding the motility coupling post, no significant difference between this zone and the vascular density found within its entire corresponding annulus was found at either 6 or 12 weeks. CONCLUSIONS: During the 6- and 12-week observation periods, all implanted motility coupling posts demonstrated favorable tissue tolerance and stable interfaces with surrounding tissues. The extent of fibrovascular tissue ingrowth and vascular density verify that initial screw insertion does not adversely affect the healing process after porous polyethylene orbital implant implantation. Thus, primary placement of the motility coupling post may obviate the need for a secondary surgical procedure.

Animals↗
PubMed2004

Phonons from powder diffraction: a quantitative model-independent evaluation.

We describe a model-independent approach for the extraction of detailed lattice dynamics information from neutron powder diffraction data, based on a statistical analysis of atomistic configurations generated using reverse Monte Carlo structural refinement. Phonon dispersion curves for MgO extracted in this way are shown to reproduce many of the important features found in those determined independently using neutron triple-axis spectroscopy. By means of molecular dynamics simulations, we quantify the extent to which the diffraction data are sensitive to lattice dynamics in this system.

Journal Article↗